Use latest language features (#2176)

* Make use of language features line AsyncDispose, init etc.

* Fix build errors

* Improve Unit Tests

* Improve Unit Tests

* Improve Unit Tests

* Update samples

* Remove obsolete benchmarks

* Code cleanup

* Improve unit tests

* Improve Unit Tests

* Fix Unit Tests

* Improve Unit Tests

* Improve Unit Tests

* Restore unit tests

* Exclude load tests from unit tests

Source/MQTTnet.AspTestApp/Pages/Index.cshtml.cs

@@ -4,20 +4,19 @@
 
 using Microsoft.AspNetCore.Mvc.RazorPages;
 
-namespace MQTTnet.AspTestApp.Pages
+namespace MQTTnet.AspTestApp.Pages;
+
+public class IndexModel : PageModel
 {
-    public class IndexModel : PageModel
+    readonly ILogger<IndexModel> _logger;
+
+    public IndexModel(ILogger<IndexModel> logger)
     {
-        private readonly ILogger<IndexModel> _logger;
+        _logger = logger;
+    }
 
-        public IndexModel(ILogger<IndexModel> logger)
-        {
-            _logger = logger;
-        }
-
-        public void OnGet()
-        {
-
-        }
+    public void OnGet()
+    {
+        _logger.LogDebug("OnGet");
     }
 }

Source/MQTTnet.AspnetCore/ApplicationBuilderExtensions.cs

@@ -33,10 +33,8 @@ public static class ApplicationBuilderExtensions
                 }
 
                 var adapter = app.ApplicationServices.GetRequiredService<MqttWebSocketServerAdapter>();
-                using (var webSocket = await context.WebSockets.AcceptWebSocketAsync(subProtocol).ConfigureAwait(false))
-                {
-                    await adapter.RunWebSocketConnectionAsync(webSocket, context);
-                }
+                using var webSocket = await context.WebSockets.AcceptWebSocketAsync(subProtocol).ConfigureAwait(false);
+                await adapter.RunWebSocketConnectionAsync(webSocket, context);
             });
 
         return app;

Source/MQTTnet.AspnetCore/ConnectionBuilderExtensions.cs

@@ -4,13 +4,12 @@
 
 using Microsoft.AspNetCore.Connections;
 
-namespace MQTTnet.AspNetCore
+namespace MQTTnet.AspNetCore;
+
+public static class ConnectionBuilderExtensions
 {
-    public static class ConnectionBuilderExtensions
+    public static IConnectionBuilder UseMqtt(this IConnectionBuilder builder)
     {
-        public static IConnectionBuilder UseMqtt(this IConnectionBuilder builder)
-        {
-            return builder.UseConnectionHandler<MqttConnectionHandler>();
-        }
+        return builder.UseConnectionHandler<MqttConnectionHandler>();
     }
-}
+}

Source/MQTTnet.AspnetCore/EndpointRouterExtensions.cs

@@ -6,19 +6,17 @@ using System;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Routing;
 
-namespace MQTTnet.AspNetCore
+namespace MQTTnet.AspNetCore;
+
+public static class EndpointRouterExtensions
 {
-    public static class EndpointRouterExtensions
+    public static void MapMqtt(this IEndpointRouteBuilder endpoints, string pattern)
     {
-        public static void MapMqtt(this IEndpointRouteBuilder endpoints, string pattern)
+        ArgumentNullException.ThrowIfNull(endpoints);
+
+        endpoints.MapConnectionHandler<MqttConnectionHandler>(pattern, options =>
         {
-            ArgumentNullException.ThrowIfNull(endpoints);
-
-            endpoints.MapConnectionHandler<MqttConnectionHandler>(pattern, options =>
-            {
-                options.WebSockets.SubProtocolSelector = MqttSubProtocolSelector.SelectSubProtocol;
-            });
-        }
+            options.WebSockets.SubProtocolSelector = MqttSubProtocolSelector.SelectSubProtocol;
+        });
     }
-}
-
+}

Source/MQTTnet.AspnetCore/MqttClientConnectionContextFactory.cs

@@ -7,28 +7,27 @@ using MQTTnet.Adapter;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Formatter;
 
-namespace MQTTnet.AspNetCore
+namespace MQTTnet.AspNetCore;
+
+public sealed class MqttClientConnectionContextFactory : IMqttClientAdapterFactory
 {
-    public sealed class MqttClientConnectionContextFactory : IMqttClientAdapterFactory
+    public IMqttChannelAdapter CreateClientAdapter(MqttClientOptions options, MqttPacketInspector packetInspector, IMqttNetLogger logger)
     {
-        public IMqttChannelAdapter CreateClientAdapter(MqttClientOptions options, MqttPacketInspector packetInspector, IMqttNetLogger logger)
+        if (options == null) throw new ArgumentNullException(nameof(options));
+
+        switch (options.ChannelOptions)
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-
-            switch (options.ChannelOptions)
+            case MqttClientTcpOptions tcpOptions:
             {
-                case MqttClientTcpOptions tcpOptions:
-                    {
-                        var tcpConnection = new SocketConnection(tcpOptions.RemoteEndpoint);
+                var tcpConnection = new SocketConnection(tcpOptions.RemoteEndpoint);
 
-                        var formatter = new MqttPacketFormatterAdapter(options.ProtocolVersion, new MqttBufferWriter(4096, 65535));
-                        return new MqttConnectionContext(formatter, tcpConnection);
-                    }
-                default:
-                    {
-                        throw new NotSupportedException();
-                    }
+                var formatter = new MqttPacketFormatterAdapter(options.ProtocolVersion, new MqttBufferWriter(4096, 65535));
+                return new MqttConnectionContext(formatter, tcpConnection);
+            }
+            default:
+            {
+                throw new NotSupportedException();
             }
         }
     }
-}
+}

Source/MQTTnet.AspnetCore/MqttConnectionHandler.cs

@@ -33,13 +33,11 @@ public sealed class MqttConnectionHandler : ConnectionHandler, IMqttServerAdapte
         }
 
         var formatter = new MqttPacketFormatterAdapter(new MqttBufferWriter(_serverOptions.WriterBufferSize, _serverOptions.WriterBufferSizeMax));
-        using (var adapter = new MqttConnectionContext(formatter, connection))
+        using var adapter = new MqttConnectionContext(formatter, connection);
+        var clientHandler = ClientHandler;
+        if (clientHandler != null)
         {
-            var clientHandler = ClientHandler;
-            if (clientHandler != null)
-            {
-                await clientHandler(adapter).ConfigureAwait(false);
-            }
+            await clientHandler(adapter).ConfigureAwait(false);
         }
     }
 

Source/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -43,10 +43,8 @@ public sealed class MqttWebSocketServerAdapter : IMqttServerAdapter
                 var formatter = new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535));
                 var channel = new MqttWebSocketChannel(webSocket, remoteEndPoint, isSecureConnection, clientCertificate);
 
-                using (var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger))
-                {
-                    await clientHandler(channelAdapter).ConfigureAwait(false);
-                }
+                using var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger);
+                await clientHandler(channelAdapter).ConfigureAwait(false);
             }
         }
         finally

Source/MQTTnet.AspnetCore/SocketAwaitable.cs

@@ -12,34 +12,28 @@ using System.Threading.Tasks;
 
 namespace MQTTnet.AspNetCore;
 
-public class SocketAwaitable : ICriticalNotifyCompletion
+public class SocketAwaitable(PipeScheduler ioScheduler) : ICriticalNotifyCompletion
 {
-    static readonly Action _callbackCompleted = () =>
+    static readonly Action CallbackCompleted = () =>
     {
     };
 
-    readonly PipeScheduler _ioScheduler;
     int _bytesTransferred;
 
     Action _callback;
     SocketError _error;
 
-    public SocketAwaitable(PipeScheduler ioScheduler)
-    {
-        _ioScheduler = ioScheduler;
-    }
-
-    public bool IsCompleted => ReferenceEquals(_callback, _callbackCompleted);
+    public bool IsCompleted => ReferenceEquals(_callback, CallbackCompleted);
 
     public void Complete(int bytesTransferred, SocketError socketError)
     {
         _error = socketError;
         _bytesTransferred = bytesTransferred;
-        var continuation = Interlocked.Exchange(ref _callback, _callbackCompleted);
+        var continuation = Interlocked.Exchange(ref _callback, CallbackCompleted);
 
         if (continuation != null)
         {
-            _ioScheduler.Schedule(state => ((Action)state)(), continuation);
+            ioScheduler.Schedule(state => ((Action)state)(), continuation);
         }
     }
 
@@ -50,7 +44,7 @@ public class SocketAwaitable : ICriticalNotifyCompletion
 
     public int GetResult()
     {
-        Debug.Assert(ReferenceEquals(_callback, _callbackCompleted));
+        Debug.Assert(ReferenceEquals(_callback, CallbackCompleted));
 
         _callback = null;
 
@@ -64,7 +58,7 @@ public class SocketAwaitable : ICriticalNotifyCompletion
 
     public void OnCompleted(Action continuation)
     {
-        if (ReferenceEquals(_callback, _callbackCompleted) || ReferenceEquals(Interlocked.CompareExchange(ref _callback, continuation, null), _callbackCompleted))
+        if (ReferenceEquals(_callback, CallbackCompleted) || ReferenceEquals(Interlocked.CompareExchange(ref _callback, continuation, null), CallbackCompleted))
         {
             Task.Run(continuation);
         }

Source/MQTTnet.AspnetCore/SocketConnection.cs

@@ -18,11 +18,11 @@ namespace MQTTnet.AspNetCore;
 public sealed class SocketConnection : ConnectionContext
 {
     readonly EndPoint _endPoint;
+
     volatile bool _aborted;
     IDuplexPipe _application;
     SocketReceiver _receiver;
     SocketSender _sender;
-
     Socket _socket;
 
     public SocketConnection(EndPoint endPoint)
@@ -40,10 +40,13 @@ public sealed class SocketConnection : ConnectionContext
     }
 
     public override string ConnectionId { get; set; }
+
     public override IFeatureCollection Features { get; }
 
     public bool IsConnected { get; private set; }
+
     public override IDictionary<object, object> Items { get; set; }
+
     public override IDuplexPipe Transport { get; set; }
 
     public override ValueTask DisposeAsync()
@@ -78,7 +81,7 @@ public sealed class SocketConnection : ConnectionContext
         IsConnected = true;
     }
 
-    Exception ConnectionAborted()
+    static Exception ConnectionAborted()
     {
         return new MqttCommunicationException("Connection Aborted");
     }
@@ -95,8 +98,7 @@ public sealed class SocketConnection : ConnectionContext
         {
             error = new MqttCommunicationException(ex);
         }
-        catch (SocketException ex) when (ex.SocketErrorCode == SocketError.OperationAborted || ex.SocketErrorCode == SocketError.ConnectionAborted ||
-                                         ex.SocketErrorCode == SocketError.Interrupted || ex.SocketErrorCode == SocketError.InvalidArgument)
+        catch (SocketException ex) when (ex.SocketErrorCode is SocketError.OperationAborted or SocketError.ConnectionAborted or SocketError.Interrupted or SocketError.InvalidArgument)
         {
             if (!_aborted)
             {
@@ -123,10 +125,10 @@ public sealed class SocketConnection : ConnectionContext
         {
             if (_aborted)
             {
-                error = error ?? ConnectionAborted();
+                error ??= ConnectionAborted();
             }
 
-            _application.Output.Complete(error);
+            await _application.Output.CompleteAsync(error);
         }
     }
 

Source/MQTTnet.Benchmarks/AsyncLockBenchmark.cs

@@ -9,57 +9,54 @@ using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Internal;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[MemoryDiagnoser]
+public class AsyncLockBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [MemoryDiagnoser]
-    public class AsyncLockBenchmark : BaseBenchmark
+    [Benchmark]
+    public async Task Synchronize_100_Tasks()
     {
-        [Benchmark]
-        public async Task Synchronize_100_Tasks()
+        const int tasksCount = 100;
+
+        var tasks = new Task[tasksCount];
+        var asyncLock = new AsyncLock();
+        var globalI = 0;
+
+        for (var i = 0; i < tasksCount; i++)
         {
-            const int tasksCount = 100;
-
-            var tasks = new Task[tasksCount];
-            var asyncLock = new AsyncLock();
-            var globalI = 0;
-
-            for (var i = 0; i < tasksCount; i++)
-            {
-                tasks[i] = Task.Run(
-                    async () =>
-                    {
-                        using (await asyncLock.EnterAsync().ConfigureAwait(false))
-                        {
-                            var localI = globalI;
-                            await Task.Delay(5).ConfigureAwait(false); // Increase the chance for wrong data.
-                            localI++;
-                            globalI = localI;
-                        }
-                    });
-            }
-
-            await Task.WhenAll(tasks).ConfigureAwait(false);
-
-            if (globalI != tasksCount)
-            {
-                throw new Exception($"Code is broken ({globalI})!");
-            }
-        }
-        
-        [Benchmark]
-        public async Task Wait_100_000_Times()
-        {
-            var asyncLock = new AsyncLock();
-
-            using (var cancellationToken = new CancellationTokenSource())
-            {
-                for (var i = 0; i < 100000; i++)
+            tasks[i] = Task.Run(
+                async () =>
                 {
-                    using (await asyncLock.EnterAsync(cancellationToken.Token).ConfigureAwait(false))
+                    using (await asyncLock.EnterAsync().ConfigureAwait(false))
                     {
+                        var localI = globalI;
+                        await Task.Delay(5).ConfigureAwait(false); // Increase the chance for wrong data.
+                        localI++;
+                        globalI = localI;
                     }
-                }
+                });
+        }
+
+        await Task.WhenAll(tasks).ConfigureAwait(false);
+
+        if (globalI != tasksCount)
+        {
+            throw new Exception($"Code is broken ({globalI})!");
+        }
+    }
+
+    [Benchmark]
+    public async Task Wait_100_000_Times()
+    {
+        var asyncLock = new AsyncLock();
+
+        using var cancellationToken = new CancellationTokenSource();
+        for (var i = 0; i < 100000; i++)
+        {
+            using (await asyncLock.EnterAsync(cancellationToken.Token).ConfigureAwait(false))
+            {
             }
         }
     }

Source/MQTTnet.Benchmarks/BaseBenchmark.cs

@@ -2,9 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+public abstract class BaseBenchmark
 {
-    public abstract class BaseBenchmark
-    {
-    }
 }

Source/MQTTnet.Benchmarks/ChannelAdapterBenchmark.cs

@@ -12,79 +12,78 @@ using MQTTnet.Formatter;
 using MQTTnet.Packets;
 using MQTTnet.Tests.Mockups;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[MemoryDiagnoser]
+public sealed class ChannelAdapterBenchmark : BaseBenchmark
 {
-    [MemoryDiagnoser]
-    public sealed class ChannelAdapterBenchmark : BaseBenchmark
+    MqttChannelAdapter _channelAdapter;
+    int _iterations;
+    MqttPublishPacket _packet;
+    MemoryStream _stream;
+
+    [Benchmark]
+    public void Receive_10000_Messages()
     {
-        MqttChannelAdapter _channelAdapter;
-        int _iterations;
-        MqttPublishPacket _packet;
-        MemoryStream _stream;
+        _stream.Position = 0;
 
-        [Benchmark]
-        public void Receive_10000_Messages()
+        for (var i = 0; i < 10000; i++)
         {
-            _stream.Position = 0;
-
-            for (var i = 0; i < 10000; i++)
-            {
-                _channelAdapter.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
-            }
-
-            _stream.Position = 0;
+            _channelAdapter.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
         }
 
-        [Benchmark]
-        public void Send_10000_Messages()
+        _stream.Position = 0;
+    }
+
+    [Benchmark]
+    public void Send_10000_Messages()
+    {
+        _stream.Position = 0;
+
+        for (var i = 0; i < 10000; i++)
         {
-            _stream.Position = 0;
-
-            for (var i = 0; i < 10000; i++)
-            {
-                _channelAdapter.SendPacketAsync(_packet, CancellationToken.None).GetAwaiter().GetResult();
-            }
-
-            _stream.Position = 0;
+            _channelAdapter.SendPacketAsync(_packet, CancellationToken.None).GetAwaiter().GetResult();
         }
 
-        [GlobalSetup]
-        public void Setup()
+        _stream.Position = 0;
+    }
+
+    [GlobalSetup]
+    public void Setup()
+    {
+        _packet = new MqttPublishPacket
         {
-            _packet = new MqttPublishPacket
-            {
-                Topic = "A"
-            };
+            Topic = "A"
+        };
 
-            var serializer = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
+        var serializer = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
 
-            var serializedPacket = Join(serializer.Encode(_packet).Join());
+        var serializedPacket = Join(serializer.Encode(_packet).Join());
 
-            _iterations = 10000;
+        _iterations = 10000;
 
-            _stream = new MemoryStream(_iterations * serializedPacket.Length);
+        _stream = new MemoryStream(_iterations * serializedPacket.Length);
 
-            for (var i = 0; i < _iterations; i++)
-            {
-                _stream.Write(serializedPacket, 0, serializedPacket.Length);
-            }
-
-            _stream.Position = 0;
-
-            var channel = new MemoryMqttChannel(_stream);
-
-            _channelAdapter = new MqttChannelAdapter(channel, serializer, new MqttNetEventLogger());
+        for (var i = 0; i < _iterations; i++)
+        {
+            _stream.Write(serializedPacket, 0, serializedPacket.Length);
         }
 
-        static byte[] Join(params ArraySegment<byte>[] chunks)
-        {
-            var buffer = new MemoryStream();
-            foreach (var chunk in chunks)
-            {
-                buffer.Write(chunk.Array, chunk.Offset, chunk.Count);
-            }
+        _stream.Position = 0;
 
-            return buffer.ToArray();
+        var channel = new MemoryMqttChannel(_stream);
+
+        _channelAdapter = new MqttChannelAdapter(channel, serializer, new MqttNetEventLogger());
+    }
+
+    static byte[] Join(params ArraySegment<byte>[] chunks)
+    {
+        var buffer = new MemoryStream();
+        foreach (var chunk in chunks)
+        {
+            buffer.Write(chunk.Array, chunk.Offset, chunk.Count);
         }
+
+        return buffer.ToArray();
     }
 }

Source/MQTTnet.Benchmarks/LoggerBenchmark.cs

@@ -2,90 +2,90 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Diagnostics;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Diagnostics.Logger;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter]
+[MemoryDiagnoser]
+public class LoggerBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter]
-    [MemoryDiagnoser]
-    public class LoggerBenchmark : BaseBenchmark
+    MqttNetNullLogger _nullLogger;
+    MqttNetSourceLogger _sourceNullLogger;
+
+    MqttNetEventLogger _eventLogger;
+    MqttNetSourceLogger _sourceEventLogger;
+
+    MqttNetEventLogger _eventLoggerNoListener;
+    MqttNetSourceLogger _sourceEventLoggerNoListener;
+
+    bool _useHandler;
+
+    [GlobalSetup]
+    public void Setup()
     {
-        MqttNetNullLogger _nullLogger;
-        MqttNetSourceLogger _sourceNullLogger;
+        _nullLogger = new MqttNetNullLogger();
+        _sourceNullLogger = _nullLogger.WithSource("Source");
 
-        MqttNetEventLogger _eventLogger;
-        MqttNetSourceLogger _sourceEventLogger;
+        _eventLogger = new MqttNetEventLogger();
+        _eventLogger.LogMessagePublished += OnLogMessagePublished;
+        _sourceEventLogger = _eventLogger.WithSource("Source");
 
-        MqttNetEventLogger _eventLoggerNoListener;
-        MqttNetSourceLogger _sourceEventLoggerNoListener;
+        _eventLoggerNoListener = new MqttNetEventLogger();
+        _sourceEventLoggerNoListener = _eventLoggerNoListener.WithSource("Source");
+    }
 
-        bool _useHandler;
-
-        [GlobalSetup]
-        public void Setup()
+    void OnLogMessagePublished(object sender, MqttNetLogMessagePublishedEventArgs eventArgs)
+    {
+        if (_useHandler)
         {
-            _nullLogger = new MqttNetNullLogger();
-            _sourceNullLogger = _nullLogger.WithSource("Source");
-
-            _eventLogger = new MqttNetEventLogger();
-            _eventLogger.LogMessagePublished += OnLogMessagePublished;
-            _sourceEventLogger = _eventLogger.WithSource("Source");
-
-            _eventLoggerNoListener = new MqttNetEventLogger();
-            _sourceEventLoggerNoListener = _eventLoggerNoListener.WithSource("Source");
-        }
-
-        void OnLogMessagePublished(object sender, MqttNetLogMessagePublishedEventArgs eventArgs)
-        {
-            if (_useHandler)
-            {
-                eventArgs.LogMessage.ToString();
-            }
-        }
-
-        [Benchmark]
-        public void Log_10000_Messages_No_Listener()
-        {
-            _useHandler = false;
-
-            for (var i = 0; i < 10000; i++)
-            {
-                _sourceEventLoggerNoListener.Verbose("test log message {0}", "parameter");
-            }
-        }
-
-        [Benchmark]
-        public void Log_10000_Messages_With_To_String()
-        {
-            _useHandler = true;
-
-            for (var i = 0; i < 10000; i++)
-            {
-                _sourceEventLogger.Verbose("test log message {0}", "parameter");
-            }
-        }
-
-        [Benchmark]
-        public void Log_10000_Messages_Without_To_String()
-        {
-            _useHandler = false;
-
-            for (var i = 0; i < 10000; i++)
-            {
-                _sourceEventLogger.Verbose("test log message {0}", "parameter");
-            }
-        }
-
-        [Benchmark]
-        public void Log_10000_Messages_With_NullLogger()
-        {
-            for (var i = 0; i < 10000; i++)
-            {
-                _sourceNullLogger.Verbose("test log message {0}", "parameter");
-            }
+            Debug.WriteLine(eventArgs.LogMessage.ToString());
         }
     }
-}
+
+    [Benchmark]
+    public void Log_10000_Messages_No_Listener()
+    {
+        _useHandler = false;
+
+        for (var i = 0; i < 10000; i++)
+        {
+            _sourceEventLoggerNoListener.Verbose("test log message {0}", "parameter");
+        }
+    }
+
+    [Benchmark]
+    public void Log_10000_Messages_With_To_String()
+    {
+        _useHandler = true;
+
+        for (var i = 0; i < 10000; i++)
+        {
+            _sourceEventLogger.Verbose("test log message {0}", "parameter");
+        }
+    }
+
+    [Benchmark]
+    public void Log_10000_Messages_Without_To_String()
+    {
+        _useHandler = false;
+
+        for (var i = 0; i < 10000; i++)
+        {
+            _sourceEventLogger.Verbose("test log message {0}", "parameter");
+        }
+    }
+
+    [Benchmark]
+    public void Log_10000_Messages_With_NullLogger()
+    {
+        for (var i = 0; i < 10000; i++)
+        {
+            _sourceNullLogger.Verbose("test log message {0}", "parameter");
+        }
+    }
+}

Source/MQTTnet.Benchmarks/MemoryCopyBenchmark.cs

@@ -3,38 +3,38 @@ using BenchmarkDotNet.Jobs;
 using System;
 
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class MemoryCopyBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter, RankColumn]
-    [MemoryDiagnoser]
-    public class MemoryCopyBenchmark
+    const int MaxLength = 1024 * 8;
+
+    byte[] _source;
+    byte[] _target;
+
+    [Params(64 - 1, 128 - 1, 256 - 1, 512 - 1, 1024 - 1, 2048 - 1, 5096 - 1)]
+    public int Length { get; set; }
+
+    [GlobalSetup]
+    public void Setup()
     {
-        const int max_length = 1024 * 8;
-        private byte[] source;
-        private byte[] target;
-
-        [Params(64 - 1, 128 - 1, 256 - 1, 512 - 1, 1024 - 1, 2048 - 1, 5096 - 1)]
-        public int Length { get; set; }
-
-        [GlobalSetup]
-        public void Setup()
-        {
-            source = new byte[max_length];
-            target = new byte[max_length];
-        }
-
-        [Benchmark(Baseline = true)]
-        public void Array_Copy()
-        {
-            Array.Copy(source, 0, target, 0, Length);
-        }
-
-        [Benchmark]
-        public void Memory_Copy()
-        {
-            MQTTnet.Internal.MqttMemoryHelper.Copy(source, 0, target, 0, Length);
-        }
-
+        _source = new byte[MaxLength];
+        _target = new byte[MaxLength];
     }
+
+    [Benchmark(Baseline = true)]
+    public void Array_Copy()
+    {
+        Array.Copy(_source, 0, _target, 0, Length);
+    }
+
+    [Benchmark]
+    public void Memory_Copy()
+    {
+        Internal.MqttMemoryHelper.Copy(_source, 0, _target, 0, Length);
+    }
+
 }

Source/MQTTnet.Benchmarks/MessageDeliveryBenchmark.cs

@@ -4,7 +4,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
@@ -23,22 +22,19 @@ public class MessageDeliveryBenchmark : BaseBenchmark
     int _messagesExpectedCount;
     int _messagesReceivedCount;
     Dictionary<string, IMqttClient> _mqttPublisherClientsByPublisherName;
-
     MqttServer _mqttServer;
     List<IMqttClient> _mqttSubscriberClients;
+
+    [Params(1000, 10000)] public int _numPublishers;
+
+    [Params(5, 10, 20, 50)] public int _numSubscribedTopicsPerSubscriber;
+
+    [Params(10)] public int _numSubscribers;
+
+    [Params(1, 5)] public int _numTopicsPerPublisher;
     Dictionary<string, string> _publisherByTopic;
-    List<MqttApplicationMessage> _topicPublishMessages;
-
     Dictionary<string, List<string>> _topicsByPublisher;
 
-    [Params(1000, 10000)] public int NumPublishers;
-
-    [Params(5, 10, 20, 50)] public int NumSubscribedTopicsPerSubscriber;
-
-    [Params(10)] public int NumSubscribers;
-
-    [Params(1, 5)] public int NumTopicsPerPublisher;
-
     [GlobalCleanup]
     public void Cleanup()
     {
@@ -64,14 +60,11 @@ public class MessageDeliveryBenchmark : BaseBenchmark
         _mqttServer = null;
     }
 
-    /// <summary>
-    ///     Publish messages and wait for messages sent to subscribers
-    /// </summary>
     [Benchmark]
     public void DeliverMessages()
     {
         // There should be one message received per publish for each subscribed topic
-        _messagesExpectedCount = NumSubscribedTopicsPerSubscriber * NumSubscribers;
+        _messagesExpectedCount = _numSubscribedTopicsPerSubscriber * _numSubscribers;
 
         // Loop for a while and exchange messages
 
@@ -82,8 +75,6 @@ public class MessageDeliveryBenchmark : BaseBenchmark
         // same payload for all messages
         var payload = new byte[] { 1, 2, 3, 4 };
 
-        var tasks = new List<Task>();
-
         // publish a message for each subscribed topic
         foreach (var topic in _allSubscribedTopics)
         {
@@ -101,35 +92,23 @@ public class MessageDeliveryBenchmark : BaseBenchmark
         }
         catch
         {
+            // Ignore all errors.
         }
 
         _cancellationTokenSource.Dispose();
 
         if (_messagesReceivedCount < _messagesExpectedCount)
         {
-            throw new Exception(string.Format("Messages Received Count mismatch, expected {0}, received {1}", _messagesExpectedCount, _messagesReceivedCount));
+            throw new Exception($"Messages Received Count mismatch, expected {_messagesExpectedCount}, received {_messagesReceivedCount}");
         }
     }
 
-
     [GlobalSetup]
     public void Setup()
     {
         _lockMsgCount = new object();
 
-        Dictionary<string, List<string>> singleWildcardTopicsByPublisher;
-        Dictionary<string, List<string>> multiWildcardTopicsByPublisher;
-
-        TopicGenerator.Generate(NumPublishers, NumTopicsPerPublisher, out _topicsByPublisher, out singleWildcardTopicsByPublisher, out multiWildcardTopicsByPublisher);
-
-        var topics = _topicsByPublisher.First().Value;
-        _topicPublishMessages = new List<MqttApplicationMessage>();
-        // Prepare messages, same for each publisher
-        foreach (var topic in topics)
-        {
-            var message = new MqttApplicationMessageBuilder().WithTopic(topic).WithPayload(new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 }).Build();
-            _topicPublishMessages.Add(message);
-        }
+        TopicGenerator.Generate(_numPublishers, _numTopicsPerPublisher, out _topicsByPublisher, out _, out _);
 
         // Create server
         var serverFactory = new MqttServerFactory();
@@ -139,7 +118,7 @@ public class MessageDeliveryBenchmark : BaseBenchmark
         _mqttServer.StartAsync().GetAwaiter().GetResult();
 
         // Create publisher clients
-        _mqttPublisherClientsByPublisherName = new Dictionary<string, IMqttClient>();
+        _mqttPublisherClientsByPublisherName = [];
         foreach (var pt in _topicsByPublisher)
         {
             var publisherName = pt.Key;
@@ -151,13 +130,13 @@ public class MessageDeliveryBenchmark : BaseBenchmark
 
         // Create subscriber clients
         _mqttSubscriberClients = new List<IMqttClient>();
-        for (var i = 0; i < NumSubscribers; i++)
+        for (var i = 0; i < _numSubscribers; i++)
         {
             var mqttSubscriberClient = clientFactory.CreateMqttClient();
             _mqttSubscriberClients.Add(mqttSubscriberClient);
 
             var subscriberOptions = new MqttClientOptionsBuilder().WithTcpServer("localhost").WithClientId("subscriber" + i).Build();
-            mqttSubscriberClient.ApplicationMessageReceivedAsync += r =>
+            mqttSubscriberClient.ApplicationMessageReceivedAsync += _ =>
             {
                 // count messages and signal cancellation when expected message count is reached
                 lock (_lockMsgCount)
@@ -171,12 +150,13 @@ public class MessageDeliveryBenchmark : BaseBenchmark
 
                 return Task.CompletedTask;
             };
+
             mqttSubscriberClient.ConnectAsync(subscriberOptions).GetAwaiter().GetResult();
         }
 
 
         var allTopics = new List<string>();
-        _publisherByTopic = new Dictionary<string, string>();
+        _publisherByTopic = [];
         foreach (var t in _topicsByPublisher)
         {
             foreach (var topic in t.Value)
@@ -189,21 +169,18 @@ public class MessageDeliveryBenchmark : BaseBenchmark
         // Subscribe to NumSubscribedTopics topics spread across all topics
         _allSubscribedTopics = new List<string>();
 
-        var totalNumTopics = NumPublishers * NumTopicsPerPublisher;
-        var topicIndexStep = totalNumTopics / (NumSubscribedTopicsPerSubscriber * NumSubscribers);
-        if (topicIndexStep * NumSubscribedTopicsPerSubscriber * NumSubscribers != totalNumTopics)
+        var totalNumTopics = _numPublishers * _numTopicsPerPublisher;
+        var topicIndexStep = totalNumTopics / (_numSubscribedTopicsPerSubscriber * _numSubscribers);
+        if (topicIndexStep * _numSubscribedTopicsPerSubscriber * _numSubscribers != totalNumTopics)
         {
             throw new Exception(
-                string.Format(
-                    "The total number of topics must be divisible by the number of subscribed topics across all subscribers. Total number of topics: {0}, topic step: {1}",
-                    totalNumTopics,
-                    topicIndexStep));
+                $"The total number of topics must be divisible by the number of subscribed topics across all subscribers. Total number of topics: {totalNumTopics}, topic step: {topicIndexStep}");
         }
 
         var topicIndex = 0;
         foreach (var mqttSubscriber in _mqttSubscriberClients)
         {
-            for (var i = 0; i < NumSubscribedTopicsPerSubscriber; ++i, topicIndex += topicIndexStep)
+            for (var i = 0; i < _numSubscribedTopicsPerSubscriber; ++i, topicIndex += topicIndexStep)
             {
                 var topic = allTopics[topicIndex];
                 _allSubscribedTopics.Add(topic);

Source/MQTTnet.Benchmarks/MessageProcessingMqttConnectionContextBenchmark.cs

@@ -9,65 +9,64 @@ using Microsoft.AspNetCore.Hosting;
 using MQTTnet.AspNetCore;
 using MQTTnet.Diagnostics.Logger;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[MemoryDiagnoser]
+public class MessageProcessingMqttConnectionContextBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [MemoryDiagnoser]
-    public class MessageProcessingMqttConnectionContextBenchmark : BaseBenchmark
+    IWebHost _host;
+    IMqttClient _mqttClient;
+    MqttApplicationMessage _message;
+
+    [GlobalSetup]
+    public void Setup()
     {
-        IWebHost _host;
-        IMqttClient _mqttClient;
-        MqttApplicationMessage _message;
+        _host = WebHost.CreateDefaultBuilder()
+            .UseKestrel(o => o.ListenAnyIP(1883, l => l.UseMqtt()))
+            .ConfigureServices(services => {
+                services
+                    .AddHostedMqttServer(mqttServerOptions => mqttServerOptions.WithoutDefaultEndpoint())
+                    .AddMqttConnectionHandler();
+            })
+            .Configure(app => {
+                app.UseMqttServer(_ => {
 
-        [GlobalSetup]
-        public void Setup()
+                });
+            })
+            .Build();
+
+        var factory = new MqttClientFactory();
+        _mqttClient = factory.CreateMqttClient(new MqttNetEventLogger(), new MqttClientConnectionContextFactory());
+
+        _host.StartAsync().GetAwaiter().GetResult();
+
+        var clientOptions = new MqttClientOptionsBuilder()
+            .WithTcpServer("localhost").Build();
+
+        _mqttClient.ConnectAsync(clientOptions).GetAwaiter().GetResult();
+
+        _message = new MqttApplicationMessageBuilder()
+            .WithTopic("A")
+            .Build();
+    }
+
+    [GlobalCleanup]
+    public void Cleanup()
+    {
+        _mqttClient.DisconnectAsync().GetAwaiter().GetResult();
+        _mqttClient.Dispose();
+
+        _host.StopAsync().GetAwaiter().GetResult();
+        _host.Dispose();
+    }
+
+    [Benchmark]
+    public void Send_10000_Messages()
+    {
+        for (var i = 0; i < 10000; i++)
         {
-            _host = WebHost.CreateDefaultBuilder()
-                   .UseKestrel(o => o.ListenAnyIP(1883, l => l.UseMqtt()))
-                   .ConfigureServices(services => {
-                        services
-                            .AddHostedMqttServer(mqttServerOptions => mqttServerOptions.WithoutDefaultEndpoint())
-                            .AddMqttConnectionHandler();
-                   })
-                   .Configure(app => {
-                       app.UseMqttServer(s => {
-
-                       });
-                   })
-                   .Build();
-
-            var factory = new MqttClientFactory();
-            _mqttClient = factory.CreateMqttClient(new MqttNetEventLogger(), new MqttClientConnectionContextFactory());
-
-            _host.StartAsync().GetAwaiter().GetResult();
-
-            var clientOptions = new MqttClientOptionsBuilder()
-                .WithTcpServer("localhost").Build();
-
-            _mqttClient.ConnectAsync(clientOptions).GetAwaiter().GetResult();
-
-            _message = new MqttApplicationMessageBuilder()
-                .WithTopic("A")
-                .Build();
-        }
-
-        [GlobalCleanup]
-        public void Cleanup()
-        {
-            _mqttClient.DisconnectAsync().GetAwaiter().GetResult();
-            _mqttClient.Dispose();
-
-            _host.StopAsync().GetAwaiter().GetResult();
-            _host.Dispose();
-        }
-
-        [Benchmark]
-        public void Send_10000_Messages()
-        {
-            for (var i = 0; i < 10000; i++)
-            {
-                _mqttClient.PublishAsync(_message).GetAwaiter().GetResult();
-            }
+            _mqttClient.PublishAsync(_message).GetAwaiter().GetResult();
         }
     }
-}
+}

Source/MQTTnet.Benchmarks/MqttBufferReaderBenchmark.cs

@@ -8,36 +8,35 @@ using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Formatter;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[MemoryDiagnoser]
+public class MqttBufferReaderBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [MemoryDiagnoser]
-    public class MqttBufferReaderBenchmark
+    byte[] _buffer;
+    int _bufferLength;
+
+    [GlobalSetup]
+    public void GlobalSetup()
     {
-        byte[] _buffer;
-        int _bufferLength;
+        var writer = new MqttBufferWriter(1024, 1024);
+        writer.WriteString("hgfjkdfkjlghfdjghdfljkdfhgdlkjfshgsldkfjghsdflkjghdsflkjhrstiuoghlkfjbhnfbutghjoiöjhklötnbhtroliöuhbjntluiobkjzbhtdrlskbhtruhjkfthgbkftgjhgfiklhotriuöhbjtrsioöbtrsötrhträhtrühjtriüoätrhjtsrölbktrbnhtrulöbionhströloubinströoliubhnsöotrunbtöroisntröointröioujhgötiohjgötorshjnbgtöorihbnjtröoihbjntröobntröoibntrjhötrohjbtröoihntröoibnrtoiöbtrjnboöitrhjtnriohötrhjtöroihjtroöihjtroösibntsroönbotöirsbntöoihjntröoihntroöbtrboöitrnhoöitrhjntröoishbnjtröosbhtröbntriohjtröoijtöoitbjöotibjnhöotirhbjntroöibhnjrtoöibnhtroöibnhtörsbnhtöoirbnhtöroibntoörhjnbträöbtrbträbtrbtirbätrsibohjntrsöiobthnjiohjsrtoib");
 
-        [GlobalSetup]
-        public void GlobalSetup()
-        {
-            var writer = new MqttBufferWriter(1024, 1024);
-            writer.WriteString("hgfjkdfkjlghfdjghdfljkdfhgdlkjfshgsldkfjghsdflkjghdsflkjhrstiuoghlkfjbhnfbutghjoiöjhklötnbhtroliöuhbjntluiobkjzbhtdrlskbhtruhjkfthgbkftgjhgfiklhotriuöhbjtrsioöbtrsötrhträhtrühjtriüoätrhjtsrölbktrbnhtrulöbionhströloubinströoliubhnsöotrunbtöroisntröointröioujhgötiohjgötorshjnbgtöorihbnjtröoihbjntröobntröoibntrjhötrohjbtröoihntröoibnrtoiöbtrjnboöitrhjtnriohötrhjtöroihjtroöihjtroösibntsroönbotöirsbntöoihjntröoihntroöbtrboöitrnhoöitrhjntröoishbnjtröosbhtröbntriohjtröoijtöoitbjöotibjnhöotirhbjntroöibhnjrtoöibnhtroöibnhtörsbnhtöoirbnhtöroibntoörhjnbträöbtrbträbtrbtirbätrsibohjntrsöiobthnjiohjsrtoib");
+        _buffer = writer.GetBuffer();
+        _bufferLength = writer.Length;
+    }
 
-            _buffer = writer.GetBuffer();
-            _bufferLength = writer.Length;
-        }
+    [Benchmark]
+    public void Use_Span()
+    {
+        var span = _buffer.AsSpan(0, _bufferLength);
+        Encoding.UTF8.GetString(span);
+    }
 
-        [Benchmark]
-        public void Use_Span()
-        {
-            var span = _buffer.AsSpan(0, _bufferLength);
-            Encoding.UTF8.GetString(span);
-        }
-        
-        [Benchmark]
-        public void Use_Encoding()
-        {
-            Encoding.UTF8.GetString(_buffer, 0, _bufferLength);
-        }
+    [Benchmark]
+    public void Use_Encoding()
+    {
+        Encoding.UTF8.GetString(_buffer, 0, _bufferLength);
     }
 }

Source/MQTTnet.Benchmarks/MqttPacketReaderWriterBenchmark.cs

@@ -8,89 +8,88 @@ using BenchmarkDotNet.Jobs;
 using MQTTnet.Formatter;
 using MQTTnet.Tests.Mockups;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[MemoryDiagnoser]
+public class MqttPacketReaderWriterBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [MemoryDiagnoser]
-    public class MqttPacketReaderWriterBenchmark : BaseBenchmark
+    readonly byte[] _demoPayload = new byte[1024];
+
+    byte[] _readPayload;
+
+    [GlobalCleanup]
+    public void GlobalCleanup()
     {
-        readonly byte[] _demoPayload = new byte[1024];
-        
-        byte[] _readPayload;
+    }
 
-        [GlobalCleanup]
-        public void GlobalCleanup()
+    [GlobalSetup]
+    public void GlobalSetup()
+    {
+        TestEnvironment.EnableLogger = false;
+
+        var writer = new MqttBufferWriter(4096, 65535);
+        writer.WriteString("A relative short string.");
+        writer.WriteBinary(_demoPayload);
+        writer.WriteByte(0x01);
+        writer.WriteByte(0x02);
+        writer.WriteVariableByteInteger(5647382);
+        writer.WriteString("A relative short string.");
+        writer.WriteVariableByteInteger(8574489);
+        writer.WriteBinary(_demoPayload);
+        writer.WriteByte(2);
+        writer.WriteByte(0x02);
+        writer.WriteString("fjgffiogfhgfhoihgoireghreghreguhreguireoghreouighreouighreughreguiorehreuiohruiorehreuioghreug");
+        writer.WriteBinary(_demoPayload);
+
+        _readPayload = new ArraySegment<byte>(writer.GetBuffer(), 0, writer.Length).ToArray();
+    }
+
+    [Benchmark]
+    public void Read_100_000_Messages()
+    {
+        var reader = new MqttBufferReader();
+        reader.SetBuffer(_readPayload, 0, _readPayload.Length);
+
+        for (var i = 0; i < 100000; i++)
         {
+            reader.Seek(0);
+
+            reader.ReadString();
+            reader.ReadBinaryData();
+            reader.ReadByte();
+            reader.ReadByte();
+            reader.ReadVariableByteInteger();
+            reader.ReadString();
+            reader.ReadVariableByteInteger();
+            reader.ReadBinaryData();
+            reader.ReadByte();
+            reader.ReadByte();
+            reader.ReadString();
+            reader.ReadBinaryData();
         }
+    }
 
-        [GlobalSetup]
-        public void GlobalSetup()
+    [Benchmark]
+    public void Write_100_000_Messages()
+    {
+        var writer = new MqttBufferWriter(4096, 65535);
+
+        for (var i = 0; i < 100000; i++)
         {
-            TestEnvironment.EnableLogger = false;
-            
-            var writer = new MqttBufferWriter(4096, 65535);
             writer.WriteString("A relative short string.");
-            writer.WriteBinary(_demoPayload);
             writer.WriteByte(0x01);
             writer.WriteByte(0x02);
             writer.WriteVariableByteInteger(5647382);
             writer.WriteString("A relative short string.");
-            writer.WriteVariableByteInteger(8574489);
+            writer.WriteVariableByteInteger(8574589);
             writer.WriteBinary(_demoPayload);
             writer.WriteByte(2);
             writer.WriteByte(0x02);
             writer.WriteString("fjgffiogfhgfhoihgoireghreghreguhreguireoghreouighreouighreughreguiorehreuiohruiorehreuioghreug");
             writer.WriteBinary(_demoPayload);
 
-            _readPayload = new ArraySegment<byte>(writer.GetBuffer(), 0, writer.Length).ToArray();
-        }
-
-        [Benchmark]
-        public void Read_100_000_Messages()
-        {
-            var reader = new MqttBufferReader();
-            reader.SetBuffer(_readPayload, 0, _readPayload.Length);
-
-            for (var i = 0; i < 100000; i++)
-            {
-                reader.Seek(0);
-
-                reader.ReadString();
-                reader.ReadBinaryData();
-                reader.ReadByte();
-                reader.ReadByte();
-                reader.ReadVariableByteInteger();
-                reader.ReadString();
-                reader.ReadVariableByteInteger();
-                reader.ReadBinaryData();
-                reader.ReadByte();
-                reader.ReadByte();
-                reader.ReadString();
-                reader.ReadBinaryData();
-            }
-        }
-        
-        [Benchmark]
-        public void Write_100_000_Messages()
-        {
-            var writer = new MqttBufferWriter(4096, 65535);
-
-            for (var i = 0; i < 100000; i++)
-            {
-                writer.WriteString("A relative short string.");
-                writer.WriteByte(0x01);
-                writer.WriteByte(0x02);
-                writer.WriteVariableByteInteger(5647382);
-                writer.WriteString("A relative short string.");
-                writer.WriteVariableByteInteger(8574589);
-                writer.WriteBinary(_demoPayload);
-                writer.WriteByte(2);
-                writer.WriteByte(0x02);
-                writer.WriteString("fjgffiogfhgfhoihgoireghreghreguhreguireoghreouighreouighreughreguiorehreuiohruiorehreuioghreug");
-                writer.WriteBinary(_demoPayload);
-
-                writer.Reset(0);
-            }
+            writer.Reset(0);
         }
     }
 }

Source/MQTTnet.Benchmarks/MqttTcpChannelBenchmark.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Buffers;
 using System.Reflection;
 using System.Threading;

Source/MQTTnet.Benchmarks/Program.cs

@@ -5,138 +5,135 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using BenchmarkDotNet.Loggers;
 using BenchmarkDotNet.Running;
-using MQTTnet.Diagnostics;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+public static class Program
 {
-    public static class Program
+    static int _selectedBenchmarkIndex;
+    static List<Type> _benchmarks;
+
+    public static void Main(string[] arguments)
     {
-        static int _selectedBenchmarkIndex;
-        static List<Type> _benchmarks;
+        _benchmarks = CollectBenchmarks();
+        HandleArguments(arguments);
 
-        public static void Main(string[] arguments)
+        while (true)
         {
-            _benchmarks = CollectBenchmarks();
-            HandleArguments(arguments);
+            RenderMenu();
 
-            while (true)
+            var key = Console.ReadKey(true);
+
+            if (key.Key == ConsoleKey.DownArrow)
             {
-                RenderMenu();
-
-                var key = Console.ReadKey(true);
-
-                if (key.Key == ConsoleKey.DownArrow)
+                _selectedBenchmarkIndex++;
+                if (_selectedBenchmarkIndex > _benchmarks.Count - 1)
                 {
-                    _selectedBenchmarkIndex++;
-                    if (_selectedBenchmarkIndex > _benchmarks.Count - 1)
-                    {
-                        _selectedBenchmarkIndex = 0;
-                    }
-                }
-                else if (key.Key == ConsoleKey.UpArrow)
-                {
-                    _selectedBenchmarkIndex--;
-                    if (_selectedBenchmarkIndex < 0)
-                    {
-                        _selectedBenchmarkIndex = _benchmarks.Count - 1;
-                    }
-                }
-                else if (key.Key == ConsoleKey.Escape)
-                {
-                    Environment.Exit(0);
-                }
-                else if (key.Key == ConsoleKey.Enter)
-                {
-                    break;
+                    _selectedBenchmarkIndex = 0;
                 }
             }
-
-            BenchmarkRunner.Run(_benchmarks[_selectedBenchmarkIndex]);
-
-            Console.ForegroundColor = ConsoleColor.Yellow;
-            Console.WriteLine("Press any key to exit");
-            Console.ReadLine();
-        }
-
-        static List<Type> CollectBenchmarks()
-        {
-            var benchmarks = new List<Type>();
-
-            var types = typeof(Program).Assembly.GetExportedTypes();
-            foreach (var type in types)
+            else if (key.Key == ConsoleKey.UpArrow)
             {
-                if (typeof(BaseBenchmark).IsAssignableFrom(type))
+                _selectedBenchmarkIndex--;
+                if (_selectedBenchmarkIndex < 0)
                 {
-                    if (type != typeof(BaseBenchmark))
-                    {
-                        benchmarks.Add(type);
-                    }
+                    _selectedBenchmarkIndex = _benchmarks.Count - 1;
                 }
             }
-
-            return benchmarks.OrderBy(b => b.Name).ToList();
-        }
-
-        static void HandleArguments(string[] arguments)
-        {
-            if (arguments.Length == 0)
+            else if (key.Key == ConsoleKey.Escape)
             {
-                return;
+                Environment.Exit(0);
             }
-
-            // Allow for preselection to avoid developer frustration.
-
-            if (int.TryParse(arguments[0], out var benchmarkIndex))
+            else if (key.Key == ConsoleKey.Enter)
             {
-                _selectedBenchmarkIndex = benchmarkIndex;
-                return;
-            }
-
-            _selectedBenchmarkIndex = _benchmarks.FindIndex(b => b.Name.Equals(arguments[0]));
-
-            if (_selectedBenchmarkIndex < 0)
-            {
-                _selectedBenchmarkIndex = 0;
-            }
-
-            if (_selectedBenchmarkIndex > _benchmarks.Count - 1)
-            {
-                _selectedBenchmarkIndex = _benchmarks.Count - 1;
+                break;
             }
         }
 
-        static void RenderMenu()
+        BenchmarkRunner.Run(_benchmarks[_selectedBenchmarkIndex]);
+
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine("Press any key to exit");
+        Console.ReadLine();
+    }
+
+    static List<Type> CollectBenchmarks()
+    {
+        var benchmarks = new List<Type>();
+
+        var types = typeof(Program).Assembly.GetExportedTypes();
+        foreach (var type in types)
         {
-            Console.Clear();
-
-            Console.WriteLine($"MQTTnet - Benchmarks");
-            Console.WriteLine("-----------------------------------------------");
-            Console.ForegroundColor = ConsoleColor.Yellow;
-            Console.WriteLine("Press arrow keys for benchmark selection");
-            Console.WriteLine("Press Enter for benchmark execution");
-            Console.WriteLine("Press Esc for exit");
-            Console.ForegroundColor = ConsoleColor.White;
-            Console.WriteLine();
-
-            for (var index = 0; index < _benchmarks.Count; index++)
+            if (typeof(BaseBenchmark).IsAssignableFrom(type))
             {
-                var benchmark = _benchmarks[index];
-
-                if (_selectedBenchmarkIndex == index)
+                if (type != typeof(BaseBenchmark))
                 {
-                    Console.Write("-> ");
+                    benchmarks.Add(type);
                 }
-                else
-                {
-                    Console.Write("   ");
-                }
-
-                Console.WriteLine(benchmark.Name);
             }
+        }
 
-            Console.WriteLine();
+        return benchmarks.OrderBy(b => b.Name).ToList();
+    }
+
+    static void HandleArguments(string[] arguments)
+    {
+        if (arguments.Length == 0)
+        {
+            return;
+        }
+
+        // Allow for preselection to avoid developer frustration.
+
+        if (int.TryParse(arguments[0], out var benchmarkIndex))
+        {
+            _selectedBenchmarkIndex = benchmarkIndex;
+            return;
+        }
+
+        _selectedBenchmarkIndex = _benchmarks.FindIndex(b => b.Name.Equals(arguments[0]));
+
+        if (_selectedBenchmarkIndex < 0)
+        {
+            _selectedBenchmarkIndex = 0;
+        }
+
+        if (_selectedBenchmarkIndex > _benchmarks.Count - 1)
+        {
+            _selectedBenchmarkIndex = _benchmarks.Count - 1;
         }
     }
+
+    static void RenderMenu()
+    {
+        Console.Clear();
+
+        Console.WriteLine($"MQTTnet - Benchmarks");
+        Console.WriteLine("-----------------------------------------------");
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine("Press arrow keys for benchmark selection");
+        Console.WriteLine("Press Enter for benchmark execution");
+        Console.WriteLine("Press Esc for exit");
+        Console.ForegroundColor = ConsoleColor.White;
+        Console.WriteLine();
+
+        for (var index = 0; index < _benchmarks.Count; index++)
+        {
+            var benchmark = _benchmarks[index];
+
+            if (_selectedBenchmarkIndex == index)
+            {
+                Console.Write("-> ");
+            }
+            else
+            {
+                Console.Write("   ");
+            }
+
+            Console.WriteLine(benchmark.Name);
+        }
+
+        Console.WriteLine();
+    }
 }

Source/MQTTnet.Benchmarks/ReaderExtensionsBenchmark.cs

@@ -1,240 +1,86 @@
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
-using MQTTnet.Adapter;
 using MQTTnet.AspNetCore;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
-using MQTTnet.Packets;
-using System;
 using System.Buffers;
 using System.IO;
 using System.IO.Pipelines;
-using System.Linq;
 using System.Threading.Tasks;
 
-namespace MQTTnet.Benchmarks
-{
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter, RankColumn]
-    [MemoryDiagnoser]
-    public class ReaderExtensionsBenchmark
-    {
-        MqttPacketFormatterAdapter mqttPacketFormatter;
-        MemoryStream stream;
+namespace MQTTnet.Benchmarks;
 
-        [GlobalSetup]
-        public void GlobalSetup()
-        {
-            mqttPacketFormatter = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
-            var mqttMessage = new MqttApplicationMessageBuilder()
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class ReaderExtensionsBenchmark
+{
+    MqttPacketFormatterAdapter _mqttPacketFormatter;
+    MemoryStream _stream;
+
+    [GlobalSetup]
+    public void GlobalSetup()
+    {
+        _mqttPacketFormatter = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
+        var mqttMessage = new MqttApplicationMessageBuilder()
             .WithTopic("topic")
             .WithPayload(new byte[10 * 1024])
             .Build();
 
-            var packet = MqttPublishPacketFactory.Create(mqttMessage);
-
-            var buffer = mqttPacketFormatter.Encode(packet);
-            stream = new MemoryStream();
-            stream.Write(buffer.Packet);
-            stream.Write(buffer.Payload.ToArray());
-            mqttPacketFormatter.Cleanup();
-        }
-
-        [Benchmark(Baseline = true)]
-        public async Task Before()
-        {
-            stream.Position = 0;
-            var input = PipeReader.Create(stream);
-
-            while (true)
-            {
-                ReadResult readResult;
-                var readTask = input.ReadAsync();
-                if (readTask.IsCompleted)
-                {
-                    readResult = readTask.Result;
-                }
-                else
-                {
-                    readResult = await readTask.ConfigureAwait(false);
-                }
-
-                var buffer = readResult.Buffer;
-
-                var consumed = buffer.Start;
-                var observed = buffer.Start;
-
-                try
-                {
-                    if (!buffer.IsEmpty)
-                    {
-                        if (ReaderExtensions_Before.TryDecode(mqttPacketFormatter, buffer, out var packet, out consumed, out observed, out var received))
-                        {
-                            break;
-                        }
-                    }
-                    else if (readResult.IsCompleted)
-                    {
-                        throw new MqttCommunicationException("Connection Aborted");
-                    }
-                }
-                finally
-                {
-                    // The buffer was sliced up to where it was consumed, so we can just advance to the start.
-                    // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
-                    // before yielding the read again.
-                    input.AdvanceTo(consumed, observed);
-                }
-            }
-        }
-
-        [Benchmark]
-        public async Task After()
-        {
-            stream.Position = 0;
-            var input = PipeReader.Create(stream);
-
-            while (true)
-            {
-                ReadResult readResult;
-                var readTask = input.ReadAsync();
-                if (readTask.IsCompleted)
-                {
-                    readResult = readTask.Result;
-                }
-                else
-                {
-                    readResult = await readTask.ConfigureAwait(false);
-                }
-
-                var buffer = readResult.Buffer;
-
-                var consumed = buffer.Start;
-                var observed = buffer.Start;
-
-                try
-                {
-                    if (!buffer.IsEmpty)
-                    {
-                        if (ReaderExtensions.TryDecode(mqttPacketFormatter, buffer, out var packet, out consumed, out observed, out var received))
-                        {
-                            break;
-                        }
-                    }
-                    else if (readResult.IsCompleted)
-                    {
-                        throw new MqttCommunicationException("Connection Aborted");
-                    }
-                }
-                finally
-                {
-                    // The buffer was sliced up to where it was consumed, so we can just advance to the start.
-                    // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
-                    // before yielding the read again.
-                    input.AdvanceTo(consumed, observed);
-                }
-            }
-        }
-
-        public static class ReaderExtensions_Before
-        {
-            public static bool TryDecode(MqttPacketFormatterAdapter formatter,
-                in ReadOnlySequence<byte> input,
-                out MqttPacket packet,
-                out SequencePosition consumed,
-                out SequencePosition observed,
-                out int bytesRead)
-            {
-                ArgumentNullException.ThrowIfNull(formatter);
-
-                packet = null;
-                consumed = input.Start;
-                observed = input.End;
-                bytesRead = 0;
-                var copy = input;
-
-                if (copy.Length < 2)
-                {
-                    return false;
-                }
-
-                var fixedHeader = copy.First.Span[0];
-                if (!TryReadBodyLength(ref copy, out int headerLength, out var bodyLength))
-                {
-                    return false;
-                }
-
-                if (copy.Length < bodyLength)
-                {
-                    return false;
-                }
-
-                var bodySlice = copy.Slice(0, bodyLength);
-                var buffer = GetMemory(bodySlice).ToArray();
-
-                var receivedMqttPacket = new ReceivedMqttPacket(fixedHeader, new ArraySegment<byte>(buffer, 0, buffer.Length), buffer.Length + 2);
-
-                if (formatter.ProtocolVersion == MqttProtocolVersion.Unknown)
-                {
-                    formatter.DetectProtocolVersion(receivedMqttPacket);
-                }
-
-                packet = formatter.Decode(receivedMqttPacket);
-                consumed = bodySlice.End;
-                observed = bodySlice.End;
-                bytesRead = headerLength + bodyLength;
-                return true;
-            }
-
-            static ReadOnlyMemory<byte> GetMemory(in ReadOnlySequence<byte> input)
-            {
-                if (input.IsSingleSegment)
-                {
-                    return input.First;
-                }
-
-                // Should be rare
-                return input.ToArray();
-            }
-
-            static bool TryReadBodyLength(ref ReadOnlySequence<byte> input, out int headerLength, out int bodyLength)
-            {
-                // Alorithm taken from https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/errata01/os/mqtt-v3.1.1-errata01-os-complete.html.
-                var multiplier = 1;
-                var value = 0;
-                byte encodedByte;
-                var index = 1;
-                headerLength = 0;
-                bodyLength = 0;
-
-                var temp = GetMemory(input.Slice(0, Math.Min(5, input.Length))).Span;
-
-                do
-                {
-                    if (index == temp.Length)
-                    {
-                        return false;
-                    }
-
-                    encodedByte = temp[index];
-                    index++;
-
-                    value += (byte)(encodedByte & 127) * multiplier;
-                    if (multiplier > 128 * 128 * 128)
-                    {
-                        throw new MqttProtocolViolationException($"Remaining length is invalid (Data={string.Join(",", temp.Slice(1, index).ToArray())}).");
-                    }
-
-                    multiplier *= 128;
-                } while ((encodedByte & 128) != 0);
-
-                input = input.Slice(index);
-
-                headerLength = index;
-                bodyLength = value;
-                return true;
-            }
-        }
+        var packet = MqttPublishPacketFactory.Create(mqttMessage);
 
+        var buffer = _mqttPacketFormatter.Encode(packet);
+        _stream = new MemoryStream();
+        _stream.Write(buffer.Packet);
+        _stream.Write(buffer.Payload.ToArray());
+        _mqttPacketFormatter.Cleanup();
     }
-}
+
+    [Benchmark]
+    public async Task After()
+    {
+        _stream.Position = 0;
+        var input = PipeReader.Create(_stream);
+
+        while (true)
+        {
+            ReadResult readResult;
+            var readTask = input.ReadAsync();
+            if (readTask.IsCompleted)
+            {
+                readResult = readTask.Result;
+            }
+            else
+            {
+                readResult = await readTask.ConfigureAwait(false);
+            }
+
+            var buffer = readResult.Buffer;
+
+            var consumed = buffer.Start;
+            var observed = buffer.Start;
+
+            try
+            {
+                if (!buffer.IsEmpty)
+                {
+                    if (_mqttPacketFormatter.TryDecode(buffer, out _, out consumed, out observed, out _))
+                    {
+                        break;
+                    }
+                }
+                else if (readResult.IsCompleted)
+                {
+                    throw new MqttCommunicationException("Connection Aborted");
+                }
+            }
+            finally
+            {
+                // The buffer was sliced up to where it was consumed, so we can just advance to the start.
+                // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
+                // before yielding the read again.
+                input.AdvanceTo(consumed, observed);
+            }
+        }
+    }
+}

Source/MQTTnet.Benchmarks/RoundtripProcessingBenchmark.cs

@@ -3,28 +3,27 @@ using BenchmarkDotNet.Jobs;
 using MQTTnet.Tests.Mockups;
 using MQTTnet.Tests.Server;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class RoundtripProcessingBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter, RankColumn]
-    [MemoryDiagnoser]
-    public class RoundtripProcessingBenchmark : BaseBenchmark
+    [GlobalSetup]
+    public void GlobalSetup()
     {
-        [GlobalSetup]
-        public void GlobalSetup()
-        {
-            TestEnvironment.EnableLogger = false;
-        }
-        
-        [GlobalCleanup]
-        public void GlobalCleanup()
-        {
-        }
-        
-        [Benchmark]
-        public void Handle_100_000_Messages_In_Receiving_Client()
-        {
-            new Load_Tests().Handle_100_000_Messages_In_Receiving_Client().GetAwaiter().GetResult();
-        }
+        TestEnvironment.EnableLogger = false;
+    }
+
+    [GlobalCleanup]
+    public void GlobalCleanup()
+    {
+    }
+
+    [Benchmark]
+    public void Handle_100_000_Messages_In_Receiving_Client()
+    {
+        new Load_Tests().Handle_100_000_Messages_In_Receiving_Client().GetAwaiter().GetResult();
     }
 }

Source/MQTTnet.Benchmarks/SendPacketAsyncBenchmark.cs

@@ -7,63 +7,61 @@ using System.IO;
 using System.IO.Pipelines;
 using System.Threading.Tasks;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class SendPacketAsyncBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter, RankColumn]
-    [MemoryDiagnoser]
-    public class SendPacketAsyncBenchmark : BaseBenchmark
+    MemoryStream _stream;
+    MqttPacketBuffer _buffer;
+
+    [GlobalSetup]
+    public void GlobalSetup()
     {
-        MemoryStream stream;
-        MqttPacketBuffer buffer;
+        _stream = new MemoryStream(1024);
+        var packet = new ArraySegment<byte>(new byte[10]);
+        _buffer = new MqttPacketBuffer(packet);
+    }
 
-        [GlobalSetup]
-        public void GlobalSetup()
+    [Benchmark(Baseline = true)]
+    public async ValueTask Before()
+    {
+        _stream.Position = 0;
+        var output = PipeWriter.Create(_stream);
+
+        WritePacketBuffer(output, _buffer);
+        await output.FlushAsync();
+    }
+
+    [Benchmark]
+    public async ValueTask After()
+    {
+        _stream.Position = 0;
+        var output = PipeWriter.Create(_stream);
+
+        if (_buffer.Payload.Length == 0)
         {
-            stream = new MemoryStream(1024);
-            var packet = new ArraySegment<byte>(new byte[10]);
-            buffer = new MqttPacketBuffer(packet);
+            await output.WriteAsync(_buffer.Packet).ConfigureAwait(false);
         }
-
-        [Benchmark(Baseline = true)]
-        public async ValueTask Before()
+        else
         {
-            stream.Position = 0;
-            var output = PipeWriter.Create(stream);
-
-            WritePacketBuffer(output, buffer);
-            await output.FlushAsync();
-        }
-
-        [Benchmark]
-        public async ValueTask After()
-        {
-            stream.Position = 0;
-            var output = PipeWriter.Create(stream);
-
-            if (buffer.Payload.Length == 0)
-            {
-                await output.WriteAsync(buffer.Packet).ConfigureAwait(false);
-            }
-            else
-            {
-                WritePacketBuffer(output, buffer);
-                await output.FlushAsync().ConfigureAwait(false);
-            }
-        }
-
-
-        static void WritePacketBuffer(PipeWriter output, MqttPacketBuffer buffer)
-        {
-            // copy MqttPacketBuffer's Packet and Payload to the same buffer block of PipeWriter
-            // MqttPacket will be transmitted within the bounds of a WebSocket frame after PipeWriter.FlushAsync
-
-            var span = output.GetSpan(buffer.Length);
-
-            buffer.Packet.AsSpan().CopyTo(span);
-            buffer.Payload.CopyTo(span.Slice(buffer.Packet.Count));
-
-            output.Advance(buffer.Length);
+            WritePacketBuffer(output, _buffer);
+            await output.FlushAsync().ConfigureAwait(false);
         }
     }
+
+    static void WritePacketBuffer(PipeWriter output, MqttPacketBuffer buffer)
+    {
+        // copy MqttPacketBuffer's Packet and Payload to the same buffer block of PipeWriter
+        // MqttPacket will be transmitted within the bounds of a WebSocket frame after PipeWriter.FlushAsync
+
+        var span = output.GetSpan(buffer.Length);
+
+        buffer.Packet.AsSpan().CopyTo(span);
+        buffer.Payload.CopyTo(span[buffer.Packet.Count..]);
+
+        output.Advance(buffer.Length);
+    }
 }

Source/MQTTnet.Benchmarks/SerializerBenchmark.cs

@@ -17,103 +17,102 @@ using MQTTnet.Diagnostics.Logger;
 using System.Buffers;
 using System.Net;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter]
+[MemoryDiagnoser]
+public class SerializerBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter]
-    [MemoryDiagnoser]
-    public class SerializerBenchmark : BaseBenchmark
+    MqttPacket _packet;
+    ArraySegment<byte> _serializedPacket;
+    IMqttPacketFormatter _serializer;
+    MqttBufferWriter _bufferWriter;
+
+    [GlobalSetup]
+    public void GlobalSetup()
     {
-        MqttPacket _packet;
-        ArraySegment<byte> _serializedPacket;
-        IMqttPacketFormatter _serializer;
-        MqttBufferWriter _bufferWriter;
-
-        [GlobalSetup]
-        public void GlobalSetup()
+        _packet = new MqttPublishPacket
         {
-            _packet = new MqttPublishPacket
-            {
-                Topic = "A"
-            };
+            Topic = "A"
+        };
 
-            _bufferWriter = new MqttBufferWriter(4096, 65535);
-            _serializer = new MqttV3PacketFormatter(_bufferWriter, MqttProtocolVersion.V311);
-            _serializedPacket = _serializer.Encode(_packet).Join();
-        }
+        _bufferWriter = new MqttBufferWriter(4096, 65535);
+        _serializer = new MqttV3PacketFormatter(_bufferWriter, MqttProtocolVersion.V311);
+        _serializedPacket = _serializer.Encode(_packet).Join();
+    }
 
-        [Benchmark]
-        public void Serialize_10000_Messages()
+    [Benchmark]
+    public void Serialize_10000_Messages()
+    {
+        for (var i = 0; i < 10000; i++)
         {
-            for (var i = 0; i < 10000; i++)
-            {
-                _serializer.Encode(_packet);
-                _bufferWriter.Cleanup();
-            }
-        }
-
-        [Benchmark]
-        public void Deserialize_10000_Messages()
-        {
-            var channel = new BenchmarkMqttChannel(_serializedPacket);
-            var reader = new MqttChannelAdapter(channel, new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535)), new MqttNetEventLogger());
-
-            for (var i = 0; i < 10000; i++)
-            {
-                channel.Reset();
-
-                var header = reader.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
-            }
-        }
-
-        class BenchmarkMqttChannel : IMqttChannel
-        {
-            readonly ArraySegment<byte> _buffer;
-            int _position;
-
-            public BenchmarkMqttChannel(ArraySegment<byte> buffer)
-            {
-                _buffer = buffer;
-                _position = _buffer.Offset;
-            }
-
-            public EndPoint RemoteEndPoint { get; set; }
-
-            public bool IsSecureConnection { get; } = false;
-
-            public X509Certificate2 ClientCertificate { get; }
-
-            public void Reset()
-            {
-                _position = _buffer.Offset;
-            }
-
-            public Task ConnectAsync(CancellationToken cancellationToken)
-            {
-                throw new NotSupportedException();
-            }
-
-            public Task DisconnectAsync(CancellationToken cancellationToken)
-            {
-                throw new NotSupportedException();
-            }
-
-            public Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
-            {
-                Array.Copy(_buffer.Array, _position, buffer, offset, count);
-                _position += count;
-
-                return Task.FromResult(count);
-            }
-
-            public Task WriteAsync(ReadOnlySequence<byte> buffer, bool isEndOfPacket, CancellationToken cancellationToken)
-            {
-                throw new NotSupportedException();
-            }
-
-            public void Dispose()
-            {
-            }
+            _serializer.Encode(_packet);
+            _bufferWriter.Cleanup();
         }
     }
-}
+
+    [Benchmark]
+    public void Deserialize_10000_Messages()
+    {
+        var channel = new BenchmarkMqttChannel(_serializedPacket);
+        var reader = new MqttChannelAdapter(channel, new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535)), new MqttNetEventLogger());
+
+        for (var i = 0; i < 10000; i++)
+        {
+            channel.Reset();
+
+            reader.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
+        }
+    }
+
+    class BenchmarkMqttChannel : IMqttChannel
+    {
+        readonly ArraySegment<byte> _buffer;
+        int _position;
+
+        public BenchmarkMqttChannel(ArraySegment<byte> buffer)
+        {
+            _buffer = buffer;
+            _position = _buffer.Offset;
+        }
+
+        public EndPoint RemoteEndPoint { get; set; }
+
+        public bool IsSecureConnection { get; } = false;
+
+        public X509Certificate2 ClientCertificate { get; set; }
+
+        public void Reset()
+        {
+            _position = _buffer.Offset;
+        }
+
+        public Task ConnectAsync(CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public Task DisconnectAsync(CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            Array.Copy(_buffer!.Array!, _position, buffer, offset, count);
+            _position += count;
+
+            return Task.FromResult(count);
+        }
+
+        public Task WriteAsync(ReadOnlySequence<byte> buffer, bool isEndOfPacket, CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}

Source/MQTTnet.Benchmarks/ServerProcessingBenchmark.cs

@@ -7,34 +7,33 @@ using BenchmarkDotNet.Jobs;
 using MQTTnet.Tests.Mockups;
 using MQTTnet.Tests.Server;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class ServerProcessingBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter, RankColumn]
-    [MemoryDiagnoser]
-    public class ServerProcessingBenchmark : BaseBenchmark
+    [GlobalSetup]
+    public void GlobalSetup()
     {
-        [GlobalSetup]
-        public void GlobalSetup()
-        {
-            TestEnvironment.EnableLogger = false;
-        }
-        
-        [GlobalCleanup]
-        public void GlobalCleanup()
-        {
-        }
-        
-        [Benchmark]
-        public void Handle_100_000_Messages_In_Server_MqttClient()
-        {
-            new Load_Tests().Handle_100_000_Messages_In_Server().GetAwaiter().GetResult();
-        }
-        
-        //[Benchmark]
-        public void Handle_100_000_Messages_In_Server_LowLevelMqttClient()
-        {
-            new Load_Tests().Handle_100_000_Messages_In_Low_Level_Client().GetAwaiter().GetResult();
-        }
+        TestEnvironment.EnableLogger = false;
+    }
+
+    [GlobalCleanup]
+    public void GlobalCleanup()
+    {
+    }
+
+    [Benchmark]
+    public void Handle_100_000_Messages_In_Server_MqttClient()
+    {
+        new Load_Tests().Handle_100_000_Messages_In_Server().GetAwaiter().GetResult();
+    }
+
+    //[Benchmark]
+    public void Handle_100_000_Messages_In_Server_LowLevelMqttClient()
+    {
+        new Load_Tests().Handle_100_000_Messages_In_Low_Level_Client().GetAwaiter().GetResult();
     }
 }

Source/MQTTnet.Benchmarks/SubscribeBenchmark.cs

@@ -30,7 +30,7 @@ public class SubscribeBenchmark : BaseBenchmark
     [GlobalSetup]
     public void Setup()
     {
-        TopicGenerator.Generate(NumPublishers, NumTopicsPerPublisher, out var topicsByPublisher, out var singleWildcardTopicsByPublisher, out var multiWildcardTopicsByPublisher);
+        TopicGenerator.Generate(NumPublishers, NumTopicsPerPublisher, out var topicsByPublisher, out _, out _);
         _topics = topicsByPublisher.Values.First();
 
         var serverOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();

Source/MQTTnet.Benchmarks/TcpPipesBenchmark.cs

@@ -11,70 +11,69 @@ using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.AspNetCore;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[MemoryDiagnoser]
+public class TcpPipesBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [MemoryDiagnoser]
-    public class TcpPipesBenchmark : BaseBenchmark
+    IDuplexPipe _client;
+    IDuplexPipe _server;
+
+    [GlobalSetup]
+    public void Setup()
     {
-        IDuplexPipe _client;
-        IDuplexPipe _server;
+        var server = new TcpListener(IPAddress.Any, 1883);
 
-        [GlobalSetup]
-        public void Setup()
+        server.Start(1);
+
+        var task = Task.Run(() => server.AcceptSocket());
+
+        var clientConnection = new SocketConnection(new IPEndPoint(IPAddress.Loopback, 1883));
+
+        clientConnection.StartAsync().GetAwaiter().GetResult();
+        _client = clientConnection.Transport;
+
+        var serverConnection = new SocketConnection(task.GetAwaiter().GetResult());
+        serverConnection.StartAsync().GetAwaiter().GetResult();
+        _server = serverConnection.Transport;
+    }
+
+
+    [Benchmark]
+    public async Task Send_10000_Chunks_Pipe()
+    {
+        var size = 5;
+        var iterations = 10000;
+
+        await Task.WhenAll(WriteAsync(iterations, size), ReadAsync(iterations, size));
+    }
+
+    async Task ReadAsync(int iterations, int size)
+    {
+        await Task.Yield();
+
+        var expected = iterations * size;
+        long read = 0;
+        var input = _client.Input;
+
+        while (read < expected)
         {
-            var server = new TcpListener(IPAddress.Any, 1883);
-
-            server.Start(1);
-
-            var task = Task.Run(() => server.AcceptSocket());
-
-            var clientConnection = new SocketConnection(new IPEndPoint(IPAddress.Loopback, 1883));
-
-            clientConnection.StartAsync().GetAwaiter().GetResult();
-            _client = clientConnection.Transport;
-
-            var serverConnection = new SocketConnection(task.GetAwaiter().GetResult());
-            serverConnection.StartAsync().GetAwaiter().GetResult();
-            _server = serverConnection.Transport;
-        }
-
-
-        [Benchmark]
-        public async Task Send_10000_Chunks_Pipe()
-        {
-            var size = 5;
-            var iterations = 10000;
-
-            await Task.WhenAll(WriteAsync(iterations, size), ReadAsync(iterations, size));
-        }
-
-        async Task ReadAsync(int iterations, int size)
-        {
-            await Task.Yield();
-
-            var expected = iterations * size;
-            long read = 0;
-            var input = _client.Input;
-
-            while (read < expected)
-            {
-                var readresult = await input.ReadAsync(CancellationToken.None).ConfigureAwait(false);
-                input.AdvanceTo(readresult.Buffer.End);
-                read += readresult.Buffer.Length;
-            }
-        }
-
-        async Task WriteAsync(int iterations, int size)
-        {
-            await Task.Yield();
-
-            var output = _server.Output;
-
-            for (var i = 0; i < iterations; i++)
-            {
-                await output.WriteAsync(new byte[size], CancellationToken.None).ConfigureAwait(false);
-            }
+            var readresult = await input.ReadAsync(CancellationToken.None).ConfigureAwait(false);
+            input.AdvanceTo(readresult.Buffer.End);
+            read += readresult.Buffer.Length;
         }
     }
-}
+
+    async Task WriteAsync(int iterations, int size)
+    {
+        await Task.Yield();
+
+        var output = _server.Output;
+
+        for (var i = 0; i < iterations; i++)
+        {
+            await output.WriteAsync(new byte[size], CancellationToken.None).ConfigureAwait(false);
+        }
+    }
+}

Source/MQTTnet.Benchmarks/TopicFilterComparerBenchmark.cs

@@ -2,269 +2,32 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter]
+[MemoryDiagnoser]
+public class TopicFilterComparerBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter]
-    [MemoryDiagnoser]
-    public class TopicFilterComparerBenchmark : BaseBenchmark
+    readonly string _longTopic =
+        "AAAAAAAAAAAAAssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
+
+    [Benchmark]
+    public void MqttTopicFilterComparer_10000_LoopMethod()
     {
-        static readonly char[] TopicLevelSeparator = { '/' };
-
-        readonly string _longTopic =
-            "AAAAAAAAAAAAAssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
-
-        [Benchmark]
-        public void MqttTopicFilterComparer_10000_LoopMethod()
+        for (var i = 0; i < 100000; i++)
         {
-            for (var i = 0; i < 100000; i++)
-            {
-                MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/#");
-                MqttTopicFilterComparer.Compare("sport/tennis/player1/ranking", "sport/#/ranking");
-                MqttTopicFilterComparer.Compare("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
-                MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/tennis/+");
-                MqttTopicFilterComparer.Compare("/finance", "+/+");
-                MqttTopicFilterComparer.Compare("/finance", "/+");
-                MqttTopicFilterComparer.Compare("/finance", "+");
-                MqttTopicFilterComparer.Compare(_longTopic, _longTopic);
-            }
-        }
-
-        [Benchmark]
-        public void MqttTopicFilterComparer_10000_LoopMethod_Without_Pointer()
-        {
-            for (var i = 0; i < 100000; i++)
-            {
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1", "sport/#");
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1/ranking", "sport/#/ranking");
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1", "sport/tennis/+");
-                MqttTopicFilterComparerWithoutPointer.Compare("/finance", "+/+");
-                MqttTopicFilterComparerWithoutPointer.Compare("/finance", "/+");
-                MqttTopicFilterComparerWithoutPointer.Compare("/finance", "+");
-                MqttTopicFilterComparerWithoutPointer.Compare(_longTopic, _longTopic);
-            }
-        }
-
-        [Benchmark]
-        public void MqttTopicFilterComparer_10000_StringSplitMethod()
-        {
-            for (var i = 0; i < 100000; i++)
-            {
-                LegacyMethodByStringSplit("sport/tennis/player1", "sport/#");
-                LegacyMethodByStringSplit("sport/tennis/player1/ranking", "sport/#/ranking");
-                LegacyMethodByStringSplit("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
-                LegacyMethodByStringSplit("sport/tennis/player1", "sport/tennis/+");
-                LegacyMethodByStringSplit("/finance", "+/+");
-                LegacyMethodByStringSplit("/finance", "/+");
-                LegacyMethodByStringSplit("/finance", "+");
-                MqttTopicFilterComparer.Compare(_longTopic, _longTopic);
-            }
-        }
-
-        [GlobalSetup]
-        public void Setup()
-        {
-        }
-
-        static bool LegacyMethodByStringSplit(string topic, string filter)
-        {
-            ArgumentNullException.ThrowIfNull(topic);
-            ArgumentNullException.ThrowIfNull(filter);
-
-            if (string.Equals(topic, filter, StringComparison.Ordinal))
-            {
-                return true;
-            }
-
-            var fragmentsTopic = topic.Split(TopicLevelSeparator, StringSplitOptions.None);
-            var fragmentsFilter = filter.Split(TopicLevelSeparator, StringSplitOptions.None);
-
-            // # > In either case it MUST be the last character specified in the Topic Filter [MQTT-4.7.1-2].
-            for (var i = 0; i < fragmentsFilter.Length; i++)
-            {
-                if (fragmentsFilter[i] == "+")
-                {
-                    continue;
-                }
-
-                if (fragmentsFilter[i] == "#")
-                {
-                    return true;
-                }
-
-                if (i >= fragmentsTopic.Length)
-                {
-                    return false;
-                }
-
-                if (!string.Equals(fragmentsFilter[i], fragmentsTopic[i], StringComparison.Ordinal))
-                {
-                    return false;
-                }
-            }
-
-            return fragmentsTopic.Length == fragmentsFilter.Length;
-        }
-
-        public static class MqttTopicFilterComparerWithoutPointer
-        {
-            public const char LevelSeparator = '/';
-            public const char MultiLevelWildcard = '#';
-            public const char SingleLevelWildcard = '+';
-            public const char ReservedTopicPrefix = '$';
-
-            public static MqttTopicFilterCompareResult Compare(string topic, string filter)
-            {
-                if (string.IsNullOrEmpty(topic))
-                {
-                    return MqttTopicFilterCompareResult.TopicInvalid;
-                }
-
-                if (string.IsNullOrEmpty(filter))
-                {
-                    return MqttTopicFilterCompareResult.FilterInvalid;
-                }
-
-                var filterOffset = 0;
-                var filterLength = filter.Length;
-
-                var topicOffset = 0;
-                var topicLength = topic.Length;
-
-                var topicPointer = topic;
-                var filterPointer = filter;
-
-                var isMultiLevelFilter = filterPointer[filterLength - 1] == MultiLevelWildcard;
-                var isReservedTopic = topicPointer[0] == ReservedTopicPrefix;
-
-                if (isReservedTopic && filterLength == 1 && isMultiLevelFilter)
-                {
-                    // It is not allowed to receive i.e. '$foo/bar' with filter '#'.
-                    return MqttTopicFilterCompareResult.NoMatch;
-                }
-
-                if (isReservedTopic && filterPointer[0] == SingleLevelWildcard)
-                {
-                    // It is not allowed to receive i.e. '$SYS/monitor/Clients' with filter '+/monitor/Clients'.
-                    return MqttTopicFilterCompareResult.NoMatch;
-                }
-
-                if (filterLength == 1 && isMultiLevelFilter)
-                {
-                    // Filter '#' matches basically everything.
-                    return MqttTopicFilterCompareResult.IsMatch;
-                }
-
-                // Go through the filter char by char.
-                while (filterOffset < filterLength && topicOffset < topicLength)
-                {
-                    // Check if the current char is a multi level wildcard. The char is only allowed
-                    // at the very las position.
-                    if (filterPointer[filterOffset] == MultiLevelWildcard && filterOffset != filterLength - 1)
-                    {
-                        return MqttTopicFilterCompareResult.FilterInvalid;
-                    }
-
-                    if (filterPointer[filterOffset] == topicPointer[topicOffset])
-                    {
-                        if (topicOffset == topicLength - 1)
-                        {
-                            // Check for e.g. "foo" matching "foo/#"
-                            if (filterOffset == filterLength - 3 && filterPointer[filterOffset + 1] == LevelSeparator && isMultiLevelFilter)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-
-                            // Check for e.g. "foo/" matching "foo/#"
-                            if (filterOffset == filterLength - 2 && filterPointer[filterOffset] == LevelSeparator && isMultiLevelFilter)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-                        }
-
-                        filterOffset++;
-                        topicOffset++;
-
-                        // Check if the end was reached and i.e. "foo/bar" matches "foo/bar"
-                        if (filterOffset == filterLength && topicOffset == topicLength)
-                        {
-                            return MqttTopicFilterCompareResult.IsMatch;
-                        }
-
-                        var endOfTopic = topicOffset == topicLength;
-
-                        if (endOfTopic && filterOffset == filterLength - 1 && filterPointer[filterOffset] == SingleLevelWildcard)
-                        {
-                            if (filterOffset > 0 && filterPointer[filterOffset - 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            return MqttTopicFilterCompareResult.IsMatch;
-                        }
-                    }
-                    else
-                    {
-                        if (filterPointer[filterOffset] == SingleLevelWildcard)
-                        {
-                            // Check for invalid "+foo" or "a/+foo" subscription
-                            if (filterOffset > 0 && filterPointer[filterOffset - 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            // Check for bad "foo+" or "foo+/a" subscription
-                            if (filterOffset < filterLength - 1 && filterPointer[filterOffset + 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            filterOffset++;
-                            while (topicOffset < topicLength && topicPointer[topicOffset] != LevelSeparator)
-                            {
-                                topicOffset++;
-                            }
-
-                            if (topicOffset == topicLength && filterOffset == filterLength)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-                        }
-                        else if (filterPointer[filterOffset] == MultiLevelWildcard)
-                        {
-                            if (filterOffset > 0 && filterPointer[filterOffset - 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            if (filterOffset + 1 != filterLength)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            return MqttTopicFilterCompareResult.IsMatch;
-                        }
-                        else
-                        {
-                            // Check for e.g. "foo/bar" matching "foo/+/#".
-                            if (filterOffset > 0 && filterOffset + 2 == filterLength && topicOffset == topicLength && filterPointer[filterOffset - 1] == SingleLevelWildcard &&
-                                filterPointer[filterOffset] == LevelSeparator && isMultiLevelFilter)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-
-                            return MqttTopicFilterCompareResult.NoMatch;
-                        }
-                    }
-                }
-
-                return MqttTopicFilterCompareResult.NoMatch;
-            }
+            MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/#");
+            MqttTopicFilterComparer.Compare("sport/tennis/player1/ranking", "sport/#/ranking");
+            MqttTopicFilterComparer.Compare("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
+            MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/tennis/+");
+            MqttTopicFilterComparer.Compare("/finance", "+/+");
+            MqttTopicFilterComparer.Compare("/finance", "/+");
+            MqttTopicFilterComparer.Compare("/finance", "+");
+            MqttTopicFilterComparer.Compare(_longTopic, _longTopic);
         }
     }
 }

Source/MQTTnet.Benchmarks/TopicGenerator.cs

@@ -1,84 +1,83 @@
 using System;
 using System.Collections.Generic;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+public class TopicGenerator
 {
-    public class TopicGenerator
+    public static void Generate(
+        int numPublishers,
+        int numTopicsPerPublisher,
+        out Dictionary<string, List<string>> topicsByPublisher,
+        out Dictionary<string, List<string>> singleWildcardTopicsByPublisher,
+        out Dictionary<string, List<string>> multiWildcardTopicsByPublisher)
     {
-        public static void Generate(
-            int numPublishers,
-            int numTopicsPerPublisher,
-            out Dictionary<string, List<string>> topicsByPublisher,
-            out Dictionary<string, List<string>> singleWildcardTopicsByPublisher,
-            out Dictionary<string, List<string>> multiWildcardTopicsByPublisher)
+        topicsByPublisher = new Dictionary<string, List<string>>();
+        singleWildcardTopicsByPublisher = new Dictionary<string, List<string>>();
+        multiWildcardTopicsByPublisher = new Dictionary<string, List<string>>();
+
+        // Find some reasonable distribution across three topic levels
+        var topicsPerLevel = (int)Math.Pow(numTopicsPerPublisher, 1.0 / 3.0);
+        if (topicsPerLevel <= 0)
         {
-            topicsByPublisher = new Dictionary<string, List<string>>();
-            singleWildcardTopicsByPublisher = new Dictionary<string, List<string>>();
-            multiWildcardTopicsByPublisher = new Dictionary<string, List<string>>();
+            topicsPerLevel = 1;
+        }
 
-            // Find some reasonable distribution across three topic levels
-            var topicsPerLevel = (int)Math.Pow(numTopicsPerPublisher, 1.0 / 3.0);
-            if (topicsPerLevel <= 0)
+        var numLevel1Topics = topicsPerLevel;
+        var numLevel2Topics = topicsPerLevel;
+
+        var maxNumLevel3Topics = 1 + (int)((double)numTopicsPerPublisher / numLevel1Topics / numLevel2Topics);
+        if (maxNumLevel3Topics <= 0)
+        {
+            maxNumLevel3Topics = 1;
+        }
+
+        for (var p = 0; p < numPublishers; ++p)
+        {
+            var publisherTopicCount = 0;
+            var publisherName = "pub" + p;
+            for (var l1 = 0; l1 < numLevel1Topics; ++l1)
             {
-                topicsPerLevel = 1;
-            }
-
-            var numLevel1Topics = topicsPerLevel;
-            var numLevel2Topics = topicsPerLevel;
-
-            var maxNumLevel3Topics = 1 + (int)((double)numTopicsPerPublisher / numLevel1Topics / numLevel2Topics);
-            if (maxNumLevel3Topics <= 0)
-            {
-                maxNumLevel3Topics = 1;
-            }
-
-            for (var p = 0; p < numPublishers; ++p)
-            {
-                var publisherTopicCount = 0;
-                var publisherName = "pub" + p;
-                for (var l1 = 0; l1 < numLevel1Topics; ++l1)
+                for (var l2 = 0; l2 < numLevel2Topics; ++l2)
                 {
-                    for (var l2 = 0; l2 < numLevel2Topics; ++l2)
+                    for (var l3 = 0; l3 < maxNumLevel3Topics; ++l3)
                     {
-                        for (var l3 = 0; l3 < maxNumLevel3Topics; ++l3)
+                        if (publisherTopicCount >= numTopicsPerPublisher)
                         {
-                            if (publisherTopicCount >= numTopicsPerPublisher)
-                            {
-                                break;
-                            }
-
-                            var topic = $"{publisherName}/building{l1 + 1}/level{l2 + 1}/sensor{l3 + 1}";
-                            AddPublisherTopic(publisherName, topic, topicsByPublisher);
-
-                            if (l2 == 0)
-                            {
-                                var singleWildcardTopic = $"{publisherName}/building{l1 + 1}/+/sensor{l3 + 1}";
-                                AddPublisherTopic(publisherName, singleWildcardTopic, singleWildcardTopicsByPublisher);
-                            }
-
-                            if (l1 == 0 && l3 == 0)
-                            {
-                                var multiWildcardTopic = $"{publisherName}/+/level{l2 + 1}/+";
-                                AddPublisherTopic(publisherName, multiWildcardTopic, multiWildcardTopicsByPublisher);
-                            }
-
-                            ++publisherTopicCount;
+                            break;
                         }
+
+                        var topic = $"{publisherName}/building{l1 + 1}/level{l2 + 1}/sensor{l3 + 1}";
+                        AddPublisherTopic(publisherName, topic, topicsByPublisher);
+
+                        if (l2 == 0)
+                        {
+                            var singleWildcardTopic = $"{publisherName}/building{l1 + 1}/+/sensor{l3 + 1}";
+                            AddPublisherTopic(publisherName, singleWildcardTopic, singleWildcardTopicsByPublisher);
+                        }
+
+                        if (l1 == 0 && l3 == 0)
+                        {
+                            var multiWildcardTopic = $"{publisherName}/+/level{l2 + 1}/+";
+                            AddPublisherTopic(publisherName, multiWildcardTopic, multiWildcardTopicsByPublisher);
+                        }
+
+                        ++publisherTopicCount;
                     }
                 }
             }
         }
+    }
 
-        static void AddPublisherTopic(string publisherName, string topic, Dictionary<string, List<string>> topicsByPublisher)
+    static void AddPublisherTopic(string publisherName, string topic, Dictionary<string, List<string>> topicsByPublisher)
+    {
+        List<string> topicList;
+        if (!topicsByPublisher.TryGetValue(publisherName, out topicList))
         {
-            List<string> topicList;
-            if (!topicsByPublisher.TryGetValue(publisherName, out topicList))
-            {
-                topicList = new List<string>();
-                topicsByPublisher.Add(publisherName, topicList);
-            }
-
-            topicList.Add(topic);
+            topicList = new List<string>();
+            topicsByPublisher.Add(publisherName, topicList);
         }
+
+        topicList.Add(topic);
     }
 }

Source/MQTTnet.Benchmarks/UnsubscribeBenchmark.cs

@@ -14,15 +14,15 @@ public class UnsubscribeBenchmark : BaseBenchmark
 {
     const int NumPublishers = 1;
     const int NumTopicsPerPublisher = 10000;
+
     IMqttClient _mqttClient;
     MqttServer _mqttServer;
-
     List<string> _topics;
 
     [GlobalSetup]
     public void Setup()
     {
-        TopicGenerator.Generate(NumPublishers, NumTopicsPerPublisher, out var topicsByPublisher, out var singleWildcardTopicsByPublisher, out var multiWildcardTopicsByPublisher);
+        TopicGenerator.Generate(NumPublishers, NumTopicsPerPublisher, out var topicsByPublisher, out _, out _);
         _topics = topicsByPublisher.Values.First();
 
         var serverOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();

Source/MQTTnet.Extensions.Rpc/DefaultMqttRpcClientTopicGenerationStrategy.cs

@@ -4,27 +4,26 @@
 
 using System;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class DefaultMqttRpcClientTopicGenerationStrategy : IMqttRpcClientTopicGenerationStrategy
 {
-    public sealed class DefaultMqttRpcClientTopicGenerationStrategy : IMqttRpcClientTopicGenerationStrategy
+    public MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context)
     {
-        public MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context)
+        ArgumentNullException.ThrowIfNull(context);
+
+        if (context.MethodName.Contains("/") || context.MethodName.Contains("+") || context.MethodName.Contains("#"))
         {
-            ArgumentNullException.ThrowIfNull(context);
-
-            if (context.MethodName.Contains("/") || context.MethodName.Contains("+") || context.MethodName.Contains("#"))
-            {
-                throw new ArgumentException("The method name cannot contain /, + or #.");
-            }
-
-            var requestTopic = $"MQTTnet.RPC/{Guid.NewGuid():N}/{context.MethodName}";
-            var responseTopic = requestTopic + "/response";
-
-            return new MqttRpcTopicPair
-            {
-                RequestTopic = requestTopic,
-                ResponseTopic = responseTopic
-            };
+            throw new ArgumentException("The method name cannot contain /, + or #.");
         }
+
+        var requestTopic = $"MQTTnet.RPC/{Guid.NewGuid():N}/{context.MethodName}";
+        var responseTopic = requestTopic + "/response";
+
+        return new MqttRpcTopicPair
+        {
+            RequestTopic = requestTopic,
+            ResponseTopic = responseTopic
+        };
     }
-}
+}

Source/MQTTnet.Extensions.Rpc/IMqttRpcClient.cs

@@ -8,12 +8,11 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public interface IMqttRpcClient : IDisposable
 {
-    public interface IMqttRpcClient : IDisposable
-    {
-        Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string,object> parameters = null);
-        
-        Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default);
-    }
+    Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string,object> parameters = null);
+
+    Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default);
 }

Source/MQTTnet.Extensions.Rpc/IMqttRpcClientTopicGenerationStrategy.cs

@@ -2,10 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public interface IMqttRpcClientTopicGenerationStrategy
 {
-    public interface IMqttRpcClientTopicGenerationStrategy
-    {
-        MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context);
-    }
-}
+    MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context);
+}

Source/MQTTnet.Extensions.Rpc/MqttFactoryExtensions.cs

@@ -4,26 +4,25 @@
 
 using System;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public static class MqttFactoryExtensions
 {
-    public static class MqttFactoryExtensions
+    public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory clientFactory, IMqttClient mqttClient)
     {
-        public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory clientFactory, IMqttClient mqttClient)
-        {
-            return clientFactory.CreateMqttRpcClient(
-                mqttClient,
-                new MqttRpcClientOptions
-                {
-                    TopicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy()
-                });
-        }
+        return clientFactory.CreateMqttRpcClient(
+            mqttClient,
+            new MqttRpcClientOptions
+            {
+                TopicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy()
+            });
+    }
 
-        public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory _, IMqttClient mqttClient, MqttRpcClientOptions rpcClientOptions)
-        {
-            ArgumentNullException.ThrowIfNull(mqttClient);
-            ArgumentNullException.ThrowIfNull(rpcClientOptions);
+    public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory _, IMqttClient mqttClient, MqttRpcClientOptions rpcClientOptions)
+    {
+        ArgumentNullException.ThrowIfNull(mqttClient);
+        ArgumentNullException.ThrowIfNull(rpcClientOptions);
 
-            return new MqttRpcClient(mqttClient, rpcClientOptions);
-        }
+        return new MqttRpcClient(mqttClient, rpcClientOptions);
     }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClient.cs

@@ -6,7 +6,6 @@ using System;
 using System.Buffers;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Exceptions;
@@ -14,128 +13,125 @@ using MQTTnet.Formatter;
 using MQTTnet.Internal;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class MqttRpcClient : IMqttRpcClient
 {
-    public sealed class MqttRpcClient : IMqttRpcClient
+    readonly IMqttClient _mqttClient;
+    readonly MqttRpcClientOptions _options;
+
+    readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>>();
+
+    public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
     {
-        readonly IMqttClient _mqttClient;
-        readonly MqttRpcClientOptions _options;
+        _mqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
+        _options = options ?? throw new ArgumentNullException(nameof(options));
 
-        readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>>();
+        _mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
+    }
 
-        public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
+    public void Dispose()
+    {
+        _mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
+
+        foreach (var tcs in _waitingCalls)
         {
-            _mqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
-            _options = options ?? throw new ArgumentNullException(nameof(options));
-
-            _mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
+            tcs.Value.TrySetCanceled();
         }
 
-        public void Dispose()
+        _waitingCalls.Clear();
+    }
+
+    public async Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null)
+    {
+        using var timeoutToken = new CancellationTokenSource(timeout);
+        try
         {
-            _mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
-
-            foreach (var tcs in _waitingCalls)
-            {
-                tcs.Value.TrySetCanceled();
-            }
-
-            _waitingCalls.Clear();
+            return await ExecuteAsync(methodName, payload, qualityOfServiceLevel, parameters, timeoutToken.Token).ConfigureAwait(false);
         }
-
-        public async Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null)
+        catch (OperationCanceledException exception)
         {
-            using (var timeoutToken = new CancellationTokenSource(timeout))
+            if (timeoutToken.IsCancellationRequested)
             {
-                try
-                {
-                    return await ExecuteAsync(methodName, payload, qualityOfServiceLevel, parameters, timeoutToken.Token).ConfigureAwait(false);
-                }
-                catch (OperationCanceledException exception)
-                {
-                    if (timeoutToken.IsCancellationRequested)
-                    {
-                        throw new MqttCommunicationTimedOutException(exception);
-                    }
-
-                    throw;
-                }
-            }
-        }
-
-        public async Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default)
-        {
-            ArgumentNullException.ThrowIfNull(methodName);
-
-            var context = new TopicGenerationContext(_mqttClient, _options, methodName, parameters, qualityOfServiceLevel);
-            var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(context);
-
-            var requestTopic = topicNames.RequestTopic;
-            var responseTopic = topicNames.ResponseTopic;
-
-            if (string.IsNullOrWhiteSpace(requestTopic))
-            {
-                throw new MqttProtocolViolationException("RPC request topic is empty.");
+                throw new MqttCommunicationTimedOutException(exception);
             }
 
-            if (string.IsNullOrWhiteSpace(responseTopic))
-            {
-                throw new MqttProtocolViolationException("RPC response topic is empty.");
-            }
-
-            var requestMessageBuilder = new MqttApplicationMessageBuilder().WithTopic(requestTopic).WithPayload(payload).WithQualityOfServiceLevel(qualityOfServiceLevel);
-
-            if (_mqttClient.Options.ProtocolVersion == MqttProtocolVersion.V500)
-            {
-                requestMessageBuilder.WithResponseTopic(responseTopic);
-            }
-
-            var requestMessage = requestMessageBuilder.Build();
-
-            try
-            {
-                var awaitable = new AsyncTaskCompletionSource<byte[]>();
-
-                if (!_waitingCalls.TryAdd(responseTopic, awaitable))
-                {
-                    throw new InvalidOperationException();
-                }
-
-                var subscribeOptions = new MqttClientSubscribeOptionsBuilder().WithTopicFilter(responseTopic, qualityOfServiceLevel).Build();
-
-                await _mqttClient.SubscribeAsync(subscribeOptions, cancellationToken).ConfigureAwait(false);
-                await _mqttClient.PublishAsync(requestMessage, cancellationToken).ConfigureAwait(false);
-
-                using (cancellationToken.Register(
-                           () =>
-                           {
-                               awaitable.TrySetCanceled();
-                           }))
-                {
-                    return await awaitable.Task.ConfigureAwait(false);
-                }
-            }
-            finally
-            {
-                _waitingCalls.TryRemove(responseTopic, out _);
-                await _mqttClient.UnsubscribeAsync(responseTopic, CancellationToken.None).ConfigureAwait(false);
-            }
-        }
-
-        Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
-        {
-            if (!_waitingCalls.TryRemove(eventArgs.ApplicationMessage.Topic, out var awaitable))
-            {
-                return CompletedTask.Instance;
-            }
-
-            var payloadBuffer = eventArgs.ApplicationMessage.Payload.ToArray();
-            awaitable.TrySetResult(payloadBuffer);
-
-            // Set this message to handled to that other code can avoid execution etc.
-            eventArgs.IsHandled = true;
-
-            return CompletedTask.Instance;
+            throw;
         }
     }
+
+    public async Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(methodName);
+
+        var context = new TopicGenerationContext(_mqttClient, _options, methodName, parameters, qualityOfServiceLevel);
+        var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(context);
+
+        var requestTopic = topicNames.RequestTopic;
+        var responseTopic = topicNames.ResponseTopic;
+
+        if (string.IsNullOrWhiteSpace(requestTopic))
+        {
+            throw new MqttProtocolViolationException("RPC request topic is empty.");
+        }
+
+        if (string.IsNullOrWhiteSpace(responseTopic))
+        {
+            throw new MqttProtocolViolationException("RPC response topic is empty.");
+        }
+
+        var requestMessageBuilder = new MqttApplicationMessageBuilder().WithTopic(requestTopic).WithPayload(payload).WithQualityOfServiceLevel(qualityOfServiceLevel);
+
+        if (_mqttClient.Options.ProtocolVersion == MqttProtocolVersion.V500)
+        {
+            requestMessageBuilder.WithResponseTopic(responseTopic);
+        }
+
+        var requestMessage = requestMessageBuilder.Build();
+
+        try
+        {
+            var awaitable = new AsyncTaskCompletionSource<byte[]>();
+
+            if (!_waitingCalls.TryAdd(responseTopic, awaitable))
+            {
+                throw new InvalidOperationException();
+            }
+
+            var subscribeOptions = new MqttClientSubscribeOptionsBuilder().WithTopicFilter(responseTopic, qualityOfServiceLevel).Build();
+
+            await _mqttClient.SubscribeAsync(subscribeOptions, cancellationToken).ConfigureAwait(false);
+            await _mqttClient.PublishAsync(requestMessage, cancellationToken).ConfigureAwait(false);
+
+            using (cancellationToken.Register(
+                       () =>
+                       {
+                           awaitable.TrySetCanceled();
+                       }))
+            {
+                return await awaitable.Task.ConfigureAwait(false);
+            }
+        }
+        finally
+        {
+            _waitingCalls.TryRemove(responseTopic, out _);
+            await _mqttClient.UnsubscribeAsync(responseTopic, CancellationToken.None).ConfigureAwait(false);
+        }
+    }
+
+    Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
+    {
+        if (!_waitingCalls.TryRemove(eventArgs.ApplicationMessage.Topic, out var awaitable))
+        {
+            return CompletedTask.Instance;
+        }
+
+        var payloadBuffer = eventArgs.ApplicationMessage.Payload.ToArray();
+        awaitable.TrySetResult(payloadBuffer);
+
+        // Set this message to handled to that other code can avoid execution etc.
+        eventArgs.IsHandled = true;
+
+        return CompletedTask.Instance;
+    }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClientExtensions.cs

@@ -8,17 +8,16 @@ using System.Text;
 using System.Threading.Tasks;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public static class MqttRpcClientExtensions
 {
-    public static class MqttRpcClientExtensions
+    public static Task<byte[]> ExecuteAsync(this IMqttRpcClient client, TimeSpan timeout, string methodName, string payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string,object> parameters = null)
     {
-        public static Task<byte[]> ExecuteAsync(this IMqttRpcClient client, TimeSpan timeout, string methodName, string payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string,object> parameters = null)
-        {
-            if (client == null) throw new ArgumentNullException(nameof(client));
+        if (client == null) throw new ArgumentNullException(nameof(client));
 
-            var buffer = Encoding.UTF8.GetBytes(payload ?? string.Empty);
+        var buffer = Encoding.UTF8.GetBytes(payload ?? string.Empty);
 
-            return client.ExecuteAsync(timeout, methodName, buffer, qualityOfServiceLevel, parameters);
-        }
+        return client.ExecuteAsync(timeout, methodName, buffer, qualityOfServiceLevel, parameters);
     }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClientOptions.cs

@@ -2,10 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class MqttRpcClientOptions
 {
-    public sealed class MqttRpcClientOptions
-    {
-        public IMqttRpcClientTopicGenerationStrategy TopicGenerationStrategy { get; set; } = new DefaultMqttRpcClientTopicGenerationStrategy();
-    }
-}
+    public IMqttRpcClientTopicGenerationStrategy TopicGenerationStrategy { get; set; } = new DefaultMqttRpcClientTopicGenerationStrategy();
+}

Source/MQTTnet.Extensions.Rpc/MqttRpcClientOptionsBuilder.cs

@@ -4,25 +4,24 @@
 
 using System;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class MqttRpcClientOptionsBuilder
 {
-    public sealed class MqttRpcClientOptionsBuilder
+    IMqttRpcClientTopicGenerationStrategy _topicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy();
+
+    public MqttRpcClientOptions Build()
     {
-        IMqttRpcClientTopicGenerationStrategy _topicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy();
-
-        public MqttRpcClientOptions Build()
+        return new MqttRpcClientOptions
         {
-            return new MqttRpcClientOptions
-            {
-                TopicGenerationStrategy = _topicGenerationStrategy
-            };
-        }
+            TopicGenerationStrategy = _topicGenerationStrategy
+        };
+    }
 
-        public MqttRpcClientOptionsBuilder WithTopicGenerationStrategy(IMqttRpcClientTopicGenerationStrategy value)
-        {
-            _topicGenerationStrategy = value ?? throw new ArgumentNullException(nameof(value));
+    public MqttRpcClientOptionsBuilder WithTopicGenerationStrategy(IMqttRpcClientTopicGenerationStrategy value)
+    {
+        _topicGenerationStrategy = value ?? throw new ArgumentNullException(nameof(value));
 
-            return this;
-        }
+        return this;
     }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcTopicPair.cs

@@ -2,12 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Extensions.Rpc
-{
-    public sealed class MqttRpcTopicPair
-    {
-        public string RequestTopic { get; set; }
+namespace MQTTnet.Extensions.Rpc;
 
-        public string ResponseTopic { get; set; }
-    }
-}
+public sealed class MqttRpcTopicPair
+{
+    public string RequestTopic { get; set; }
+
+    public string ResponseTopic { get; set; }
+}

Source/MQTTnet.Extensions.Rpc/TopicGenerationContext.cs

@@ -6,37 +6,36 @@ using System;
 using System.Collections.Generic;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class TopicGenerationContext
 {
-    public sealed class TopicGenerationContext
+    public TopicGenerationContext(IMqttClient mqttClient, MqttRpcClientOptions options, string methodName,
+        IDictionary<string, object> parameters, MqttQualityOfServiceLevel qualityOfServiceLevel)
     {
-        public TopicGenerationContext(IMqttClient mqttClient, MqttRpcClientOptions options, string methodName,
-            IDictionary<string, object> parameters, MqttQualityOfServiceLevel qualityOfServiceLevel)
-        {
-            MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
-            Parameters = parameters;
-            QualityOfServiceLevel = qualityOfServiceLevel;
-            MqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
-            Options = options ?? throw new ArgumentNullException(nameof(options));
-        }
-
-        public string MethodName { get; }
-
-        public IDictionary<string, object> Parameters { get; }
-
-        public IMqttClient MqttClient { get; }
-
-        public MqttRpcClientOptions Options { get; }
-
-        /// <summary>
-        ///     Gets or sets the quality of service level.
-        ///     The Quality of Service (QoS) level is an agreement between the sender of a message and the receiver of a message
-        ///     that defines the guarantee of delivery for a specific message.
-        ///     There are 3 QoS levels in MQTT:
-        ///     - At most once  (0): Message gets delivered no time, once or multiple times.
-        ///     - At least once (1): Message gets delivered at least once (one time or more often).
-        ///     - Exactly once  (2): Message gets delivered exactly once (It's ensured that the message only comes once).
-        /// </summary>
-        public MqttQualityOfServiceLevel QualityOfServiceLevel { get; }
+        MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
+        Parameters = parameters;
+        QualityOfServiceLevel = qualityOfServiceLevel;
+        MqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
+        Options = options ?? throw new ArgumentNullException(nameof(options));
     }
+
+    public string MethodName { get; }
+
+    public IDictionary<string, object> Parameters { get; }
+
+    public IMqttClient MqttClient { get; }
+
+    public MqttRpcClientOptions Options { get; }
+
+    /// <summary>
+    ///     Gets or sets the quality of service level.
+    ///     The Quality of Service (QoS) level is an agreement between the sender of a message and the receiver of a message
+    ///     that defines the guarantee of delivery for a specific message.
+    ///     There are 3 QoS levels in MQTT:
+    ///     - At most once  (0): Message gets delivered no time, once or multiple times.
+    ///     - At least once (1): Message gets delivered at least once (one time or more often).
+    ///     - Exactly once  (2): Message gets delivered exactly once (It's ensured that the message only comes once).
+    /// </summary>
+    public MqttQualityOfServiceLevel QualityOfServiceLevel { get; }
 }

Source/MQTTnet.Extensions.TopicTemplate/MQTTnet.Extensions.TopicTemplate.csproj

@@ -47,7 +47,7 @@
 
     <ItemGroup>
         <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
-        <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+        <PackageReference Include="System.ValueTuple" Version="4.6.1" />
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.Extensions.TopicTemplate/MqttTopicTemplate.cs

@@ -230,7 +230,7 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
             throw new ArgumentException("the topic has to match this template", nameof(topic));
         }
 
-        return parseParameterValuesInternal(topic);
+        return ParseParameterValuesInternal(topic);
     }
 
     /// <summary>
@@ -330,7 +330,7 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
         return parameters.Aggregate(this, (t, p) => t.TrySetParameter(p.parameter, p.value));
     }
 
-    IEnumerable<(string parameter, int index, string value)> parseParameterValuesInternal(string topic)
+    IEnumerable<(string parameter, int index, string value)> ParseParameterValuesInternal(string topic)
     {
         // because we have a match, we know the segment array is at least the template's length
         var segments = topic.Split(MqttTopicFilterComparer.LevelSeparator);

Source/MQTTnet.Server/Disconnecting/MqttServerClientDisconnectOptions.cs

@@ -5,28 +5,27 @@
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class MqttServerClientDisconnectOptions
 {
-    public sealed class MqttServerClientDisconnectOptions
-    {
-        public MqttDisconnectReasonCode ReasonCode { get; set; } = MqttDisconnectReasonCode.NormalDisconnection;
+    public MqttDisconnectReasonCode ReasonCode { get; set; } = MqttDisconnectReasonCode.NormalDisconnection;
 
-        /// <summary>
-        ///     The reason string is sent to every client via a DISCONNECT packet.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public string ReasonString { get; set; }
+    /// <summary>
+    ///     The reason string is sent to every client via a DISCONNECT packet.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public string ReasonString { get; set; }
 
-        /// <summary>
-        ///     The server reference is sent to every client via a DISCONNECT packet.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public string ServerReference { get; set; }
+    /// <summary>
+    ///     The server reference is sent to every client via a DISCONNECT packet.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public string ServerReference { get; set; }
 
-        /// <summary>
-        ///     These user properties are sent to every client via a DISCONNECT packet.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties { get; set; }
-    }
+    /// <summary>
+    ///     These user properties are sent to every client via a DISCONNECT packet.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/Disconnecting/MqttServerClientDisconnectOptionsBuilder.cs

@@ -5,50 +5,49 @@
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class MqttServerClientDisconnectOptionsBuilder
 {
-    public sealed class MqttServerClientDisconnectOptionsBuilder
+    readonly MqttServerClientDisconnectOptions _options = new MqttServerClientDisconnectOptions();
+
+    public MqttServerClientDisconnectOptions Build()
     {
-        readonly MqttServerClientDisconnectOptions _options = new MqttServerClientDisconnectOptions();
+        return _options;
+    }
 
-        public MqttServerClientDisconnectOptions Build()
+    public MqttServerClientDisconnectOptionsBuilder WithReasonCode(MqttDisconnectReasonCode value)
+    {
+        _options.ReasonCode = value;
+        return this;
+    }
+
+    public MqttServerClientDisconnectOptionsBuilder WithReasonString(string value)
+    {
+        _options.ReasonString = value;
+        return this;
+    }
+
+    public MqttServerClientDisconnectOptionsBuilder WithServerReference(string value)
+    {
+        _options.ServerReference = value;
+        return this;
+    }
+
+    public MqttServerClientDisconnectOptionsBuilder WithUserProperties(List<MqttUserProperty> value)
+    {
+        _options.UserProperties = value;
+        return this;
+    }
+
+    public MqttServerClientDisconnectOptionsBuilder WithUserProperty(string name, string value)
+    {
+        if (_options.UserProperties == null)
         {
-            return _options;
+            _options.UserProperties = new List<MqttUserProperty>();
         }
 
-        public MqttServerClientDisconnectOptionsBuilder WithReasonCode(MqttDisconnectReasonCode value)
-        {
-            _options.ReasonCode = value;
-            return this;
-        }
-
-        public MqttServerClientDisconnectOptionsBuilder WithReasonString(string value)
-        {
-            _options.ReasonString = value;
-            return this;
-        }
-
-        public MqttServerClientDisconnectOptionsBuilder WithServerReference(string value)
-        {
-            _options.ServerReference = value;
-            return this;
-        }
-
-        public MqttServerClientDisconnectOptionsBuilder WithUserProperties(List<MqttUserProperty> value)
-        {
-            _options.UserProperties = value;
-            return this;
-        }
-
-        public MqttServerClientDisconnectOptionsBuilder WithUserProperty(string name, string value)
-        {
-            if (_options.UserProperties == null)
-            {
-                _options.UserProperties = new List<MqttUserProperty>();
-            }
-
-            _options.UserProperties.Add(new MqttUserProperty(name, value));
-            return this;
-        }
+        _options.UserProperties.Add(new MqttUserProperty(name, value));
+        return this;
     }
 }

Source/MQTTnet.Server/Events/ApplicationMessageEnqueuedEventArgs.cs

@@ -2,26 +2,23 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class ApplicationMessageEnqueuedEventArgs : EventArgs
 {
-    public sealed class ApplicationMessageEnqueuedEventArgs : EventArgs
+    public ApplicationMessageEnqueuedEventArgs(string senderClientId, string receiverClientId, MqttApplicationMessage applicationMessage, bool isDropped)
     {
-        public ApplicationMessageEnqueuedEventArgs(string senderClientId, string receiverClientId, MqttApplicationMessage applicationMessage, bool isDropped)
-        {
-            SenderClientId = senderClientId ?? throw new ArgumentNullException( nameof(senderClientId));
-            ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
-            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
-            IsDropped = isDropped;
-        }
-
-        public string SenderClientId { get; }
-
-        public string ReceiverClientId { get; }
-
-        public bool IsDropped { get; }
-
-        public MqttApplicationMessage ApplicationMessage { get; }
+        SenderClientId = senderClientId ?? throw new ArgumentNullException( nameof(senderClientId));
+        ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
+        ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+        IsDropped = isDropped;
     }
+
+    public string SenderClientId { get; }
+
+    public string ReceiverClientId { get; }
+
+    public bool IsDropped { get; }
+
+    public MqttApplicationMessage ApplicationMessage { get; }
 }

Source/MQTTnet.Server/Events/ApplicationMessageNotConsumedEventArgs.cs

@@ -2,26 +2,23 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class ApplicationMessageNotConsumedEventArgs : EventArgs
 {
-    public sealed class ApplicationMessageNotConsumedEventArgs : EventArgs
+    public ApplicationMessageNotConsumedEventArgs(MqttApplicationMessage applicationMessage, string senderId)
     {
-        public ApplicationMessageNotConsumedEventArgs(MqttApplicationMessage applicationMessage, string senderId)
-        {
-            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
-            SenderId = senderId;
-        }
-
-        /// <summary>
-        ///     Gets the application message which was not consumed by any client.
-        /// </summary>
-        public MqttApplicationMessage ApplicationMessage { get; }
-
-        /// <summary>
-        ///     Gets the ID of the client which has sent the affected application message.
-        /// </summary>
-        public string SenderId { get; }
+        ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+        SenderId = senderId;
     }
+
+    /// <summary>
+    ///     Gets the application message which was not consumed by any client.
+    /// </summary>
+    public MqttApplicationMessage ApplicationMessage { get; }
+
+    /// <summary>
+    ///     Gets the ID of the client which has sent the affected application message.
+    /// </summary>
+    public string SenderId { get; }
 }

Source/MQTTnet.Server/Events/ClientAcknowledgedPublishPacketEventArgs.cs

@@ -2,51 +2,49 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientAcknowledgedPublishPacketEventArgs : EventArgs
 {
-    public sealed class ClientAcknowledgedPublishPacketEventArgs : EventArgs
+    public ClientAcknowledgedPublishPacketEventArgs(string clientId, string userName, IDictionary sessionItems, MqttPublishPacket publishPacket, MqttPacketWithIdentifier acknowledgePacket)
     {
-        public ClientAcknowledgedPublishPacketEventArgs(string clientId, string userName, IDictionary sessionItems, MqttPublishPacket publishPacket, MqttPacketWithIdentifier acknowledgePacket)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            UserName = userName;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-            PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
-            AcknowledgePacket = acknowledgePacket ?? throw new ArgumentNullException(nameof(acknowledgePacket));
-        }
-        
-        /// <summary>
-        ///     Gets the packet which was used for acknowledge. This can be a PubAck or PubComp packet.
-        /// </summary>
-        public MqttPacketWithIdentifier AcknowledgePacket { get; }
-
-        /// <summary>
-        ///     Gets the ID of the client which acknowledged a PUBLISH packet.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; }
-
-        /// <summary>
-        ///     Gets whether the PUBLISH packet is fully acknowledged. This is the case for PUBACK (QoS 1) and PUBCOMP (QoS 2.
-        /// </summary>
-        public bool IsCompleted => AcknowledgePacket is MqttPubAckPacket || AcknowledgePacket is MqttPubCompPacket;
-
-        /// <summary>
-        ///     Gets the PUBLISH packet which was acknowledged.
-        /// </summary>
-        public MqttPublishPacket PublishPacket { get; }
-
-        /// <summary>
-        ///     Gets the session items which contain custom user data per session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
+        PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
+        AcknowledgePacket = acknowledgePacket ?? throw new ArgumentNullException(nameof(acknowledgePacket));
     }
+
+    /// <summary>
+    ///     Gets the packet which was used for acknowledge. This can be a PubAck or PubComp packet.
+    /// </summary>
+    public MqttPacketWithIdentifier AcknowledgePacket { get; }
+
+    /// <summary>
+    ///     Gets the ID of the client which acknowledged a PUBLISH packet.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets whether the PUBLISH packet is fully acknowledged. This is the case for PUBACK (QoS 1) and PUBCOMP (QoS 2.
+    /// </summary>
+    public bool IsCompleted => AcknowledgePacket is MqttPubAckPacket || AcknowledgePacket is MqttPubCompPacket;
+
+    /// <summary>
+    ///     Gets the PUBLISH packet which was acknowledged.
+    /// </summary>
+    public MqttPublishPacket PublishPacket { get; }
+
+    /// <summary>
+    ///     Gets the session items which contain custom user data per session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/ClientConnectedEventArgs.cs

@@ -2,70 +2,67 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Net;
 using System.Text;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientConnectedEventArgs : EventArgs
 {
-    public sealed class ClientConnectedEventArgs : EventArgs
+    readonly MqttConnectPacket _connectPacket;
+
+    public ClientConnectedEventArgs(MqttConnectPacket connectPacket, MqttProtocolVersion protocolVersion, EndPoint remoteEndPoint, IDictionary sessionItems)
     {
-        readonly MqttConnectPacket _connectPacket;
-
-        public ClientConnectedEventArgs(MqttConnectPacket connectPacket, MqttProtocolVersion protocolVersion, EndPoint remoteEndPoint, IDictionary sessionItems)
-        {
-            _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
-            ProtocolVersion = protocolVersion;
-            RemoteEndPoint = remoteEndPoint;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        public byte[] AuthenticationData => _connectPacket.AuthenticationData;
-
-        public string AuthenticationMethod => _connectPacket.AuthenticationMethod;
-
-        /// <summary>
-        ///     Gets the client identifier of the connected client.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId => _connectPacket.ClientId;
-
-        /// <summary>
-        ///     Gets the endpoint of the connected client.
-        /// </summary>
-        public EndPoint RemoteEndPoint { get; }
-
-        [Obsolete("Use RemoteEndPoint instead.")]
-        public string Endpoint => RemoteEndPoint?.ToString();
-
-        /// <summary>
-        ///     Gets the protocol version which is used by the connected client.
-        /// </summary>
-        public MqttProtocolVersion ProtocolVersion { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets the user name of the connected client.
-        /// </summary>
-        public string UserName => _connectPacket.Username;
-
-        /// <summary>
-        ///     Gets the password of the connected client.
-        /// </summary>
-        public string Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
-
-        /// <summary>
-        ///     Gets the user properties sent by the client.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties => _connectPacket?.UserProperties;
+        _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
+        ProtocolVersion = protocolVersion;
+        RemoteEndPoint = remoteEndPoint;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    public byte[] AuthenticationData => _connectPacket.AuthenticationData;
+
+    public string AuthenticationMethod => _connectPacket.AuthenticationMethod;
+
+    /// <summary>
+    ///     Gets the client identifier of the connected client.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId => _connectPacket.ClientId;
+
+    /// <summary>
+    ///     Gets the endpoint of the connected client.
+    /// </summary>
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string Endpoint => RemoteEndPoint?.ToString();
+
+    /// <summary>
+    ///     Gets the protocol version which is used by the connected client.
+    /// </summary>
+    public MqttProtocolVersion ProtocolVersion { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the user name of the connected client.
+    /// </summary>
+    public string UserName => _connectPacket.Username;
+
+    /// <summary>
+    ///     Gets the password of the connected client.
+    /// </summary>
+    public string Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
+
+    /// <summary>
+    ///     Gets the user properties sent by the client.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties => _connectPacket?.UserProperties;
 }

Source/MQTTnet.Server/Events/ClientDisconnectedEventArgs.cs

@@ -2,91 +2,88 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Net;
 using System.Text;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientDisconnectedEventArgs : EventArgs
 {
-    public sealed class ClientDisconnectedEventArgs : EventArgs
+    readonly MqttConnectPacket _connectPacket;
+    readonly MqttDisconnectPacket _disconnectPacket;
+
+    public ClientDisconnectedEventArgs(
+        MqttConnectPacket connectPacket,
+        MqttDisconnectPacket disconnectPacket,
+        MqttClientDisconnectType disconnectType,
+        EndPoint remoteEndPoint,
+        IDictionary sessionItems)
     {
-        readonly MqttConnectPacket _connectPacket;
-        readonly MqttDisconnectPacket _disconnectPacket;
+        DisconnectType = disconnectType;
+        RemoteEndPoint = remoteEndPoint;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
 
-        public ClientDisconnectedEventArgs(
-            MqttConnectPacket connectPacket,
-            MqttDisconnectPacket disconnectPacket,
-            MqttClientDisconnectType disconnectType,
-            EndPoint remoteEndPoint,
-            IDictionary sessionItems)
-        {
-            DisconnectType = disconnectType;
-            RemoteEndPoint = remoteEndPoint;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-
-            _connectPacket = connectPacket;
-            // The DISCONNECT packet can be null in case of a non clean disconnect or session takeover.
-            _disconnectPacket = disconnectPacket;
-        }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId => _connectPacket.ClientId;
-
-        /// <summary>
-        ///     Gets the user name of the client.
-        /// </summary>
-        public string UserName => _connectPacket.Username;
-
-        /// <summary>
-        ///     Gets the password of the client.
-        /// </summary>
-        public string Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
-
-        public MqttClientDisconnectType DisconnectType { get; }
-
-        public EndPoint RemoteEndPoint { get; }
-
-        [Obsolete("Use RemoteEndPoint instead.")]
-        public string Endpoint => RemoteEndPoint?.ToString();
-
-        /// <summary>
-        ///     Gets the reason code sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public MqttDisconnectReasonCode? ReasonCode => _disconnectPacket?.ReasonCode;
-
-        /// <summary>
-        ///     Gets the reason string sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public string ReasonString => _disconnectPacket?.ReasonString;
-
-        /// <summary>
-        ///     Gets the session expiry interval sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public uint SessionExpiryInterval => _disconnectPacket?.SessionExpiryInterval ?? 0;
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets the user properties sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties => _disconnectPacket?.UserProperties;
+        _connectPacket = connectPacket;
+        // The DISCONNECT packet can be null in case of a non clean disconnect or session takeover.
+        _disconnectPacket = disconnectPacket;
     }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId => _connectPacket.ClientId;
+
+    /// <summary>
+    ///     Gets the user name of the client.
+    /// </summary>
+    public string UserName => _connectPacket.Username;
+
+    /// <summary>
+    ///     Gets the password of the client.
+    /// </summary>
+    public string Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
+
+    public MqttClientDisconnectType DisconnectType { get; }
+
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string Endpoint => RemoteEndPoint?.ToString();
+
+    /// <summary>
+    ///     Gets the reason code sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public MqttDisconnectReasonCode? ReasonCode => _disconnectPacket?.ReasonCode;
+
+    /// <summary>
+    ///     Gets the reason string sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public string ReasonString => _disconnectPacket?.ReasonString;
+
+    /// <summary>
+    ///     Gets the session expiry interval sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public uint SessionExpiryInterval => _disconnectPacket?.SessionExpiryInterval ?? 0;
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the user properties sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties => _disconnectPacket?.UserProperties;
 }

Source/MQTTnet.Server/Events/ClientSubscribedTopicEventArgs.cs

@@ -2,42 +2,40 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientSubscribedTopicEventArgs : EventArgs
 {
-    public sealed class ClientSubscribedTopicEventArgs : EventArgs
+    public ClientSubscribedTopicEventArgs(string clientId, string userName, MqttTopicFilter topicFilter, IDictionary sessionItems)
     {
-        public ClientSubscribedTopicEventArgs(string clientId, string userName, MqttTopicFilter topicFilter, IDictionary sessionItems)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            UserName = userName;
-            TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets the topic filter.
-        ///     The topic filter can contain topics and wildcards.
-        /// </summary>
-        public MqttTopicFilter TopicFilter { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the topic filter.
+    ///     The topic filter can contain topics and wildcards.
+    /// </summary>
+    public MqttTopicFilter TopicFilter { get; }
 }

Source/MQTTnet.Server/Events/ClientUnsubscribedTopicEventArgs.cs

@@ -2,41 +2,39 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientUnsubscribedTopicEventArgs : EventArgs
 {
-    public sealed class ClientUnsubscribedTopicEventArgs : EventArgs
+    public ClientUnsubscribedTopicEventArgs(string clientId, string userName, string topicFilter, IDictionary sessionItems)
     {
-        public ClientUnsubscribedTopicEventArgs(string clientId, string userName, string topicFilter, IDictionary sessionItems)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            UserName = userName;
-            TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets or sets the topic filter.
-        ///     The topic filter can contain topics and wildcards.
-        /// </summary>
-        public string TopicFilter { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets or sets the topic filter.
+    ///     The topic filter can contain topics and wildcards.
+    /// </summary>
+    public string TopicFilter { get; }
 }

Source/MQTTnet.Server/Events/InterceptingClientApplicationMessageEnqueueEventArgs.cs

@@ -2,34 +2,31 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class InterceptingClientApplicationMessageEnqueueEventArgs : EventArgs
 {
-    public sealed class InterceptingClientApplicationMessageEnqueueEventArgs : EventArgs
+    public InterceptingClientApplicationMessageEnqueueEventArgs(string senderClientId, string receiverClientId, MqttApplicationMessage applicationMessage)
     {
-        public InterceptingClientApplicationMessageEnqueueEventArgs(string senderClientId, string receiverClientId, MqttApplicationMessage applicationMessage)
-        {
-            SenderClientId = senderClientId ?? throw new ArgumentNullException(nameof(senderClientId));
-            ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
-            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
-        }
-
-        /// <summary>
-        ///     Gets or sets whether the enqueue of the application message should be performed or not.
-        ///     If set to _False_ the client will not receive the application message.
-        /// </summary>
-        public bool AcceptEnqueue { get; set; } = true;
-
-        public MqttApplicationMessage ApplicationMessage { get; }
-
-        /// <summary>
-        ///     Indicates if the connection with the sender should be closed.
-        /// </summary>
-        public bool CloseSenderConnection { get; set; }
-
-        public string ReceiverClientId { get; }
-
-        public string SenderClientId { get; }
+        SenderClientId = senderClientId ?? throw new ArgumentNullException(nameof(senderClientId));
+        ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
+        ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
     }
+
+    /// <summary>
+    ///     Gets or sets whether the enqueue of the application message should be performed or not.
+    ///     If set to _False_ the client will not receive the application message.
+    /// </summary>
+    public bool AcceptEnqueue { get; set; } = true;
+
+    public MqttApplicationMessage ApplicationMessage { get; }
+
+    /// <summary>
+    ///     Indicates if the connection with the sender should be closed.
+    /// </summary>
+    public bool CloseSenderConnection { get; set; }
+
+    public string ReceiverClientId { get; }
+
+    public string SenderClientId { get; }
 }

Source/MQTTnet.Server/Events/InterceptingPacketEventArgs.cs

@@ -2,63 +2,60 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 using System.Net;
-using System.Threading;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingPacketEventArgs : EventArgs
 {
-    public sealed class InterceptingPacketEventArgs : EventArgs
+    public InterceptingPacketEventArgs(CancellationToken cancellationToken, string clientId, string userName, EndPoint remoteEndPoint, MqttPacket packet, IDictionary sessionItems)
     {
-        public InterceptingPacketEventArgs(CancellationToken cancellationToken, string clientId, string userName, EndPoint remoteEndPoint, MqttPacket packet, IDictionary sessionItems)
-        {
-            CancellationToken = cancellationToken;
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            UserName = userName;
-            RemoteEndPoint = remoteEndPoint;
-            Packet = packet ?? throw new ArgumentNullException(nameof(packet));
-            SessionItems = sessionItems;
-        }
-
-        /// <summary>
-        ///     Gets the cancellation token from the connection managing thread.
-        ///     Use this in further event processing.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client ID which has sent the packet or will receive the packet.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; }
-
-        /// <summary>
-        ///     Gets the endpoint of the sending or receiving client.
-        /// </summary>
-        public EndPoint RemoteEndPoint { get; }
-
-        [Obsolete("Use RemoteEndPoint instead.")]
-        public string Endpoint => RemoteEndPoint?.ToString();
-
-        /// <summary>
-        ///     Gets or sets the MQTT packet which was received or will be sent.
-        /// </summary>
-        public MqttPacket Packet { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the packet should be processed or not.
-        /// </summary>
-        public bool ProcessPacket { get; set; } = true;
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        CancellationToken = cancellationToken;
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        RemoteEndPoint = remoteEndPoint;
+        Packet = packet ?? throw new ArgumentNullException(nameof(packet));
+        SessionItems = sessionItems;
     }
+
+    /// <summary>
+    ///     Gets the cancellation token from the connection managing thread.
+    ///     Use this in further event processing.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client ID which has sent the packet or will receive the packet.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets the endpoint of the sending or receiving client.
+    /// </summary>
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string Endpoint => RemoteEndPoint?.ToString();
+
+    /// <summary>
+    ///     Gets or sets the MQTT packet which was received or will be sent.
+    /// </summary>
+    public MqttPacket Packet { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the packet should be processed or not.
+    /// </summary>
+    public bool ProcessPacket { get; set; } = true;
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/InterceptingPublishEventArgs.cs

@@ -2,56 +2,53 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Threading;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingPublishEventArgs : EventArgs
 {
-    public sealed class InterceptingPublishEventArgs : EventArgs
+    public InterceptingPublishEventArgs(MqttApplicationMessage applicationMessage, CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems)
     {
-        public InterceptingPublishEventArgs(MqttApplicationMessage applicationMessage, CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems)
-        {
-            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
-            CancellationToken = cancellationToken;
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            UserName = userName;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        public MqttApplicationMessage ApplicationMessage { get; set; }
-
-        /// <summary>
-        ///     Gets the cancellation token which can indicate that the client connection gets down.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; }
-
-        public bool CloseConnection { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the publish should be processed internally.
-        /// </summary>
-        public bool ProcessPublish { get; set; } = true;
-
-        /// <summary>
-        ///     Gets the response which will be sent to the client via the PUBACK etc. packets.
-        /// </summary>
-        public PublishResponse Response { get; } = new PublishResponse();
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+        CancellationToken = cancellationToken;
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    public MqttApplicationMessage ApplicationMessage { get; set; }
+
+    /// <summary>
+    ///     Gets the cancellation token which can indicate that the client connection gets down.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    public bool CloseConnection { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the publish should be processed internally.
+    /// </summary>
+    public bool ProcessPublish { get; set; } = true;
+
+    /// <summary>
+    ///     Gets the response which will be sent to the client via the PUBACK etc. packets.
+    /// </summary>
+    public PublishResponse Response { get; } = new PublishResponse();
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/InterceptingSubscriptionEventArgs.cs

@@ -2,90 +2,86 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingSubscriptionEventArgs : EventArgs
 {
-    public sealed class InterceptingSubscriptionEventArgs : EventArgs
+    public InterceptingSubscriptionEventArgs(
+        CancellationToken cancellationToken,
+        string clientId,
+        string userName,
+        MqttSessionStatus session,
+        MqttTopicFilter topicFilter,
+        List<MqttUserProperty> userProperties)
     {
-        public InterceptingSubscriptionEventArgs(
-            CancellationToken cancellationToken,
-            string clientId,
-            string userName,
-            MqttSessionStatus session,
-            MqttTopicFilter topicFilter,
-            List<MqttUserProperty> userProperties)
-        {
-            CancellationToken = cancellationToken;
-            ClientId = clientId;
-            UserName = userName;
-            Session = session;
-            TopicFilter = topicFilter;
-            UserProperties = userProperties;
-        }
-
-        /// <summary>
-        ///     Gets the cancellation token which can indicate that the client connection gets down.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should close the client connection.
-        /// </summary>
-        public bool CloseConnection { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should create an internal subscription for the client.
-        ///     The broker can also avoid this and return "success" to the client.
-        ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
-        /// </summary>
-        public bool ProcessSubscription { get; set; } = true;
-
-        /// <summary>
-        ///     Gets or sets the reason string which will be sent to the client in the SUBACK packet.
-        /// </summary>
-        public string ReasonString { get; set; }
-
-        /// <summary>
-        ///     Gets the response which will be sent to the client via the SUBACK packet.
-        /// </summary>
-        public SubscribeResponse Response { get; } = new SubscribeResponse();
-
-        /// <summary>
-        ///     Gets the current client session.
-        /// </summary>
-        public MqttSessionStatus Session { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems => Session.Items;
-
-        /// <summary>
-        ///     Gets or sets the topic filter.
-        ///     The topic filter can contain topics and wildcards.
-        /// </summary>
-        public MqttTopicFilter TopicFilter { get; set; }
-
-        /// <summary>
-        ///     Gets or sets the user properties.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties { get; set; }
+        CancellationToken = cancellationToken;
+        ClientId = clientId;
+        UserName = userName;
+        Session = session;
+        TopicFilter = topicFilter;
+        UserProperties = userProperties;
     }
+
+    /// <summary>
+    ///     Gets the cancellation token which can indicate that the client connection gets down.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should close the client connection.
+    /// </summary>
+    public bool CloseConnection { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should create an internal subscription for the client.
+    ///     The broker can also avoid this and return "success" to the client.
+    ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
+    /// </summary>
+    public bool ProcessSubscription { get; set; } = true;
+
+    /// <summary>
+    ///     Gets or sets the reason string which will be sent to the client in the SUBACK packet.
+    /// </summary>
+    public string ReasonString { get; set; }
+
+    /// <summary>
+    ///     Gets the response which will be sent to the client via the SUBACK packet.
+    /// </summary>
+    public SubscribeResponse Response { get; } = new SubscribeResponse();
+
+    /// <summary>
+    ///     Gets the current client session.
+    /// </summary>
+    public MqttSessionStatus Session { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems => Session.Items;
+
+    /// <summary>
+    ///     Gets or sets the topic filter.
+    ///     The topic filter can contain topics and wildcards.
+    /// </summary>
+    public MqttTopicFilter TopicFilter { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the user properties.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/Events/InterceptingUnsubscriptionEventArgs.cs

@@ -2,77 +2,73 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingUnsubscriptionEventArgs : EventArgs
 {
-    public sealed class InterceptingUnsubscriptionEventArgs : EventArgs
+    public InterceptingUnsubscriptionEventArgs(CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems, string topic, List<MqttUserProperty> userProperties)
     {
-        public InterceptingUnsubscriptionEventArgs(CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems, string topic, List<MqttUserProperty> userProperties)
-        {
-            CancellationToken = cancellationToken;
-            ClientId = clientId;
-            UserName = userName;
-            SessionItems = sessionItems;
-            Topic = topic;
-            UserProperties = userProperties;
-        }
-
-        /// <summary>
-        ///     Gets the cancellation token which can indicate that the client connection gets down.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        /// Gets the user name of the client.
-        /// </summary>
-        public string UserName { get; } 
-
-        /// <summary>
-        ///     Gets or sets whether the broker should close the client connection.
-        /// </summary>
-        public bool CloseConnection { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should remove an internal subscription for the client.
-        ///     The broker can also avoid this and return "success" to the client.
-        ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
-        /// </summary>
-        public bool ProcessUnsubscription { get; set; } = true;
-
-        /// <summary>
-        ///     Gets the response which will be sent to the client via the UNSUBACK pocket.
-        /// </summary>
-        public UnsubscribeResponse Response { get; } = new UnsubscribeResponse();
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets or sets the MQTT topic.
-        ///     In MQTT, the word topic refers to an UTF-8 string that the broker uses to filter messages for each connected
-        ///     client.
-        ///     The topic consists of one or more topic levels. Each topic level is separated by a forward slash (topic level
-        ///     separator).
-        /// </summary>
-        public string Topic { get; }
-
-        /// <summary>
-        ///     Gets or sets the user properties.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties { get; set; }
+        CancellationToken = cancellationToken;
+        ClientId = clientId;
+        UserName = userName;
+        SessionItems = sessionItems;
+        Topic = topic;
+        UserProperties = userProperties;
     }
+
+    /// <summary>
+    ///     Gets the cancellation token which can indicate that the client connection gets down.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should close the client connection.
+    /// </summary>
+    public bool CloseConnection { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should remove an internal subscription for the client.
+    ///     The broker can also avoid this and return "success" to the client.
+    ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
+    /// </summary>
+    public bool ProcessUnsubscription { get; set; } = true;
+
+    /// <summary>
+    ///     Gets the response which will be sent to the client via the UNSUBACK pocket.
+    /// </summary>
+    public UnsubscribeResponse Response { get; } = new UnsubscribeResponse();
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets or sets the MQTT topic.
+    ///     In MQTT, the word topic refers to an UTF-8 string that the broker uses to filter messages for each connected
+    ///     client.
+    ///     The topic consists of one or more topic levels. Each topic level is separated by a forward slash (topic level
+    ///     separator).
+    /// </summary>
+    public string Topic { get; }
+
+    /// <summary>
+    ///     Gets or sets the user properties.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/Events/LoadingRetainedMessagesEventArgs.cs

@@ -2,13 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class LoadingRetainedMessagesEventArgs : EventArgs
 {
-    public sealed class LoadingRetainedMessagesEventArgs : EventArgs
-    {
-        public List<MqttApplicationMessage> LoadedRetainedMessages { get; set; } = new List<MqttApplicationMessage>();
-    }
+    public List<MqttApplicationMessage> LoadedRetainedMessages { get; set; } = new List<MqttApplicationMessage>();
 }

Source/MQTTnet.Server/Events/PreparingSessionEventArgs.cs

@@ -2,50 +2,47 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
 using MQTTnet.Packets;
 using MQTTnet.Server.Internal;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class PreparingSessionEventArgs : EventArgs
 {
-    public sealed class PreparingSessionEventArgs : EventArgs
-    {
-        public string Id { get; set; }
+    public string Id { get; set; }
 
-        // TODO: Allow adding of packets to the queue etc.
+    // TODO: Allow adding of packets to the queue etc.
 
-        /*
-         * The Session State in the Server consists of:
+    /*
+     * The Session State in the Server consists of:
 ·         The existence of a Session, even if the rest of the Session State is empty.
 ·         The Clients subscriptions, including any Subscription Identifiers.
 ·         QoS 1 and QoS 2 messages which have been sent to the Client, but have not been completely acknowledged.
 ·         QoS 1 and QoS 2 messages pending transmission to the Client and OPTIONALLY QoS 0 messages pending transmission to the Client.
 ·         QoS 2 messages which have been received from the Client, but have not been completely acknowledged.The Will Message and the Will Delay Interval
 ·         If the Session is currently not connected, the time at which the Session will end and Session State will be discarded.
-         */
+     */
 
-        public bool IsExistingSession { get; set; }
+    public bool IsExistingSession { get; set; }
 
-        public IDictionary<object, object> Items { get; set; }
+    public IDictionary<object, object> Items { get; set; }
 
-        public List<MqttPublishPacket> PublishPackets { get; } = new List<MqttPublishPacket>();
+    public List<MqttPublishPacket> PublishPackets { get; } = new List<MqttPublishPacket>();
 
-        DateTime? SessionExpiryTimestamp { get; set; }
+    DateTime? SessionExpiryTimestamp { get; set; }
 
-        public List<MqttSubscription> Subscriptions { get; } = new List<MqttSubscription>();
+    public List<MqttSubscription> Subscriptions { get; } = new List<MqttSubscription>();
 
-        /// <summary>
-        ///     Gets the will delay interval.
-        ///     This is the time between the client disconnect and the time the will message will be sent.
-        /// </summary>
-        public uint? WillDelayInterval { get; set; }
+    /// <summary>
+    ///     Gets the will delay interval.
+    ///     This is the time between the client disconnect and the time the will message will be sent.
+    /// </summary>
+    public uint? WillDelayInterval { get; set; }
 
-        // <summary>
-        //     Gets the last will message.
-        //     In MQTT, you use the last will message feature to notify other clients about an ungracefully disconnected client.
-        // </summary>
-        // TODO: Use single properties. No entire will message.
-        //MqttApplicationMessage WillMessage { get; set; }
-    }
+    // <summary>
+    //     Gets the last will message.
+    //     In MQTT, you use the last will message feature to notify other clients about an ungracefully disconnected client.
+    // </summary>
+    // TODO: Use single properties. No entire will message.
+    //MqttApplicationMessage WillMessage { get; set; }
 }

Source/MQTTnet.Server/Events/QueueMessageOverwrittenEventArgs.cs

@@ -2,21 +2,19 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class QueueMessageOverwrittenEventArgs : EventArgs
 {
-    public sealed class QueueMessageOverwrittenEventArgs : EventArgs
+    public QueueMessageOverwrittenEventArgs(string receiverClientId, MqttPacket packet)
     {
-        public QueueMessageOverwrittenEventArgs(string receiverClientId, MqttPacket packet)
-        {
-            ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
-            Packet = packet ?? throw new ArgumentNullException(nameof(packet));
-        }
-
-        public MqttPacket Packet { get; }
-
-        public string ReceiverClientId { get; }
+        ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
+        Packet = packet ?? throw new ArgumentNullException(nameof(packet));
     }
+
+    public MqttPacket Packet { get; }
+
+    public string ReceiverClientId { get; }
 }

Source/MQTTnet.Server/Events/RetainedMessageChangedEventArgs.cs

@@ -2,24 +2,20 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class RetainedMessageChangedEventArgs : EventArgs
 {
-    public sealed class RetainedMessageChangedEventArgs : EventArgs
+    public RetainedMessageChangedEventArgs(string clientId, MqttApplicationMessage changedRetainedMessage, List<MqttApplicationMessage> storedRetainedMessages)
     {
-        public RetainedMessageChangedEventArgs(string clientId, MqttApplicationMessage changedRetainedMessage, List<MqttApplicationMessage> storedRetainedMessages)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            ChangedRetainedMessage = changedRetainedMessage ?? throw new ArgumentNullException(nameof(changedRetainedMessage));
-            StoredRetainedMessages = storedRetainedMessages ?? throw new ArgumentNullException(nameof(storedRetainedMessages));
-        }
-
-        public MqttApplicationMessage ChangedRetainedMessage { get; }
-
-        public string ClientId { get; }
-
-        public List<MqttApplicationMessage> StoredRetainedMessages { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        ChangedRetainedMessage = changedRetainedMessage ?? throw new ArgumentNullException(nameof(changedRetainedMessage));
+        StoredRetainedMessages = storedRetainedMessages ?? throw new ArgumentNullException(nameof(storedRetainedMessages));
     }
+
+    public MqttApplicationMessage ChangedRetainedMessage { get; }
+
+    public string ClientId { get; }
+
+    public List<MqttApplicationMessage> StoredRetainedMessages { get; }
 }

Source/MQTTnet.Server/Events/SessionDeletedEventArgs.cs

@@ -2,33 +2,31 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class SessionDeletedEventArgs : EventArgs
 {
-    public sealed class SessionDeletedEventArgs : EventArgs
+    public SessionDeletedEventArgs(string id, string userName, IDictionary sessionItems)
     {
-        public SessionDeletedEventArgs(string id, string userName, IDictionary sessionItems)
-        {
-            Id = id ?? throw new ArgumentNullException(nameof(id));
-            UserName = userName;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        /// <summary>
-        ///     Gets the ID of the session.
-        /// </summary>
-        public string Id { get; }
-
-        /// <summary>
-        /// Gets the user name of the session.
-        /// </summary>
-        public string UserName { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        Id = id ?? throw new ArgumentNullException(nameof(id));
+        UserName = userName;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    /// <summary>
+    ///     Gets the ID of the session.
+    /// </summary>
+    public string Id { get; }
+
+    /// <summary>
+    /// Gets the user name of the session.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Internal/Adapter/MqttTcpServerAdapter.cs

@@ -8,118 +8,117 @@ using MQTTnet.Adapter;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Internal;
 
-namespace MQTTnet.Server.Internal.Adapter
+namespace MQTTnet.Server.Internal.Adapter;
+
+public sealed class MqttTcpServerAdapter : IMqttServerAdapter
 {
-    public sealed class MqttTcpServerAdapter : IMqttServerAdapter
+    readonly List<MqttTcpServerListener> _listeners = new List<MqttTcpServerListener>();
+
+    CancellationTokenSource _cancellationTokenSource;
+
+    MqttServerOptions _serverOptions;
+
+    public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
+
+    public bool TreatSocketOpeningErrorAsWarning { get; set; }
+
+    public void Dispose()
     {
-        readonly List<MqttTcpServerListener> _listeners = new List<MqttTcpServerListener>();
+        Cleanup();
+    }
 
-        CancellationTokenSource _cancellationTokenSource;
-
-        MqttServerOptions _serverOptions;
-
-        public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
-
-        public bool TreatSocketOpeningErrorAsWarning { get; set; }
-
-        public void Dispose()
+    public Task StartAsync(MqttServerOptions options, IMqttNetLogger logger)
+    {
+        if (_cancellationTokenSource != null)
         {
-            Cleanup();
+            throw new InvalidOperationException("Server is already started.");
         }
 
-        public Task StartAsync(MqttServerOptions options, IMqttNetLogger logger)
+        _serverOptions = options;
+
+        _cancellationTokenSource = new CancellationTokenSource();
+
+        if (options.DefaultEndpointOptions.IsEnabled)
         {
-            if (_cancellationTokenSource != null)
+            RegisterListeners(options.DefaultEndpointOptions, logger, _cancellationTokenSource.Token);
+        }
+
+        if (options.TlsEndpointOptions?.IsEnabled == true)
+        {
+            if (options.TlsEndpointOptions.CertificateProvider == null)
             {
-                throw new InvalidOperationException("Server is already started.");
+                throw new ArgumentException("TLS certificate is not set.");
             }
 
-            _serverOptions = options;
+            RegisterListeners(options.TlsEndpointOptions, logger, _cancellationTokenSource.Token);
+        }
 
-            _cancellationTokenSource = new CancellationTokenSource();
+        return CompletedTask.Instance;
+    }
 
-            if (options.DefaultEndpointOptions.IsEnabled)
+    public Task StopAsync()
+    {
+        Cleanup();
+        return CompletedTask.Instance;
+    }
+
+    void Cleanup()
+    {
+        try
+        {
+            _cancellationTokenSource?.Cancel(false);
+        }
+        finally
+        {
+            _cancellationTokenSource?.Dispose();
+            _cancellationTokenSource = null;
+
+            foreach (var listener in _listeners)
             {
-                RegisterListeners(options.DefaultEndpointOptions, logger, _cancellationTokenSource.Token);
+                listener.Dispose();
             }
 
-            if (options.TlsEndpointOptions?.IsEnabled == true)
-            {
-                if (options.TlsEndpointOptions.CertificateProvider == null)
-                {
-                    throw new ArgumentException("TLS certificate is not set.");
-                }
-
-                RegisterListeners(options.TlsEndpointOptions, logger, _cancellationTokenSource.Token);
-            }
+            _listeners.Clear();
+        }
+    }
 
+    Task OnClientAcceptedAsync(IMqttChannelAdapter channelAdapter)
+    {
+        var clientHandler = ClientHandler;
+        if (clientHandler == null)
+        {
             return CompletedTask.Instance;
         }
 
-        public Task StopAsync()
+        return clientHandler(channelAdapter);
+    }
+
+    void RegisterListeners(MqttServerTcpEndpointBaseOptions tcpEndpointOptions, IMqttNetLogger logger, CancellationToken cancellationToken)
+    {
+        if (!tcpEndpointOptions.BoundInterNetworkAddress.Equals(IPAddress.None))
         {
-            Cleanup();
-            return CompletedTask.Instance;
-        }
-
-        void Cleanup()
-        {
-            try
+            var listenerV4 = new MqttTcpServerListener(AddressFamily.InterNetwork, _serverOptions, tcpEndpointOptions, logger)
             {
-                _cancellationTokenSource?.Cancel(false);
-            }
-            finally
+                ClientHandler = OnClientAcceptedAsync
+            };
+
+            if (listenerV4.Start(TreatSocketOpeningErrorAsWarning, cancellationToken))
             {
-                _cancellationTokenSource?.Dispose();
-                _cancellationTokenSource = null;
-
-                foreach (var listener in _listeners)
-                {
-                    listener.Dispose();
-                }
-
-                _listeners.Clear();
+                _listeners.Add(listenerV4);
             }
         }
 
-        Task OnClientAcceptedAsync(IMqttChannelAdapter channelAdapter)
+        if (!tcpEndpointOptions.BoundInterNetworkV6Address.Equals(IPAddress.None))
         {
-            var clientHandler = ClientHandler;
-            if (clientHandler == null)
+            var listenerV6 = new MqttTcpServerListener(AddressFamily.InterNetworkV6, _serverOptions, tcpEndpointOptions, logger)
             {
-                return CompletedTask.Instance;
-            }
+                ClientHandler = OnClientAcceptedAsync
+            };
 
-            return clientHandler(channelAdapter);
-        }
-
-        void RegisterListeners(MqttServerTcpEndpointBaseOptions tcpEndpointOptions, IMqttNetLogger logger, CancellationToken cancellationToken)
-        {
-            if (!tcpEndpointOptions.BoundInterNetworkAddress.Equals(IPAddress.None))
+            if (listenerV6.Start(TreatSocketOpeningErrorAsWarning, cancellationToken))
             {
-                var listenerV4 = new MqttTcpServerListener(AddressFamily.InterNetwork, _serverOptions, tcpEndpointOptions, logger)
-                {
-                    ClientHandler = OnClientAcceptedAsync
-                };
-
-                if (listenerV4.Start(TreatSocketOpeningErrorAsWarning, cancellationToken))
-                {
-                    _listeners.Add(listenerV4);
-                }
-            }
-
-            if (!tcpEndpointOptions.BoundInterNetworkV6Address.Equals(IPAddress.None))
-            {
-                var listenerV6 = new MqttTcpServerListener(AddressFamily.InterNetworkV6, _serverOptions, tcpEndpointOptions, logger)
-                {
-                    ClientHandler = OnClientAcceptedAsync
-                };
-
-                if (listenerV6.Start(TreatSocketOpeningErrorAsWarning, cancellationToken))
-                {
-                    _listeners.Add(listenerV6);
-                }
+                _listeners.Add(listenerV6);
             }
         }
     }
-}
+}

Source/MQTTnet.Server/Internal/Adapter/MqttTcpServerListener.cs

@@ -12,248 +12,247 @@ using MQTTnet.Formatter;
 using MQTTnet.Implementations;
 using MQTTnet.Internal;
 
-namespace MQTTnet.Server.Internal.Adapter
+namespace MQTTnet.Server.Internal.Adapter;
+
+public sealed class MqttTcpServerListener : IDisposable
 {
-    public sealed class MqttTcpServerListener : IDisposable
+    readonly MqttNetSourceLogger _logger;
+    readonly IMqttNetLogger _rootLogger;
+    readonly AddressFamily _addressFamily;
+    readonly MqttServerOptions _serverOptions;
+    readonly MqttServerTcpEndpointBaseOptions _options;
+    readonly MqttServerTlsTcpEndpointOptions _tlsOptions;
+
+    CrossPlatformSocket _socket;
+    IPEndPoint _localEndPoint;
+
+    public MqttTcpServerListener(
+        AddressFamily addressFamily,
+        MqttServerOptions serverOptions,
+        MqttServerTcpEndpointBaseOptions tcpEndpointOptions,
+        IMqttNetLogger logger)
     {
-        readonly MqttNetSourceLogger _logger;
-        readonly IMqttNetLogger _rootLogger;
-        readonly AddressFamily _addressFamily;
-        readonly MqttServerOptions _serverOptions;
-        readonly MqttServerTcpEndpointBaseOptions _options;
-        readonly MqttServerTlsTcpEndpointOptions _tlsOptions;
+        _addressFamily = addressFamily;
+        _serverOptions = serverOptions ?? throw new ArgumentNullException(nameof(serverOptions));
+        _options = tcpEndpointOptions ?? throw new ArgumentNullException(nameof(tcpEndpointOptions));
+        _rootLogger = logger;
+        _logger = logger.WithSource(nameof(MqttTcpServerListener));
 
-        CrossPlatformSocket _socket;
-        IPEndPoint _localEndPoint;
-
-        public MqttTcpServerListener(
-            AddressFamily addressFamily,
-            MqttServerOptions serverOptions,
-            MqttServerTcpEndpointBaseOptions tcpEndpointOptions,
-            IMqttNetLogger logger)
+        if (_options is MqttServerTlsTcpEndpointOptions tlsOptions)
         {
-            _addressFamily = addressFamily;
-            _serverOptions = serverOptions ?? throw new ArgumentNullException(nameof(serverOptions));
-            _options = tcpEndpointOptions ?? throw new ArgumentNullException(nameof(tcpEndpointOptions));
-            _rootLogger = logger;
-            _logger = logger.WithSource(nameof(MqttTcpServerListener));
-
-            if (_options is MqttServerTlsTcpEndpointOptions tlsOptions)
-            {
-                _tlsOptions = tlsOptions;
-            }
+            _tlsOptions = tlsOptions;
         }
+    }
 
-        public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
+    public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
 
-        public bool Start(bool treatErrorsAsWarning, CancellationToken cancellationToken)
+    public bool Start(bool treatErrorsAsWarning, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var boundIp = _options.BoundInterNetworkAddress;
+            if (_addressFamily == AddressFamily.InterNetworkV6)
+            {
+                boundIp = _options.BoundInterNetworkV6Address;
+            }
+
+            _localEndPoint = new IPEndPoint(boundIp, _options.Port);
+
+            _logger.Info("Starting TCP listener (Endpoint={0}, TLS={1})", _localEndPoint, _tlsOptions?.CertificateProvider != null);
+
+            _socket = new CrossPlatformSocket(_addressFamily, ProtocolType.Tcp);
+
+            // Usage of socket options is described here: https://docs.microsoft.com/en-us/dotnet/api/system.net.sockets.socket.setsocketoption?view=netcore-2.2
+            if (_options.ReuseAddress)
+            {
+                _socket.ReuseAddress = true;
+            }
+
+            if (_options.NoDelay)
+            {
+                _socket.NoDelay = true;
+            }
+
+            if (_options.LingerState != null)
+            {
+                _socket.LingerState = _options.LingerState;
+            }
+
+            if (_options.KeepAlive.HasValue)
+            {
+                _socket.KeepAlive = _options.KeepAlive.Value;
+            }
+
+            if (_options.TcpKeepAliveInterval.HasValue)
+            {
+                _socket.TcpKeepAliveInterval = _options.TcpKeepAliveInterval.Value;
+            }
+
+            if (_options.TcpKeepAliveRetryCount.HasValue)
+            {
+                _socket.TcpKeepAliveInterval = _options.TcpKeepAliveRetryCount.Value;
+            }
+
+            if (_options.TcpKeepAliveTime.HasValue)
+            {
+                _socket.TcpKeepAliveTime = _options.TcpKeepAliveTime.Value;
+            }
+
+            _socket.Bind(_localEndPoint);
+
+            // Get the local endpoint back from the socket. The port may have changed.
+            // This can happen when port 0 is used. Then the OS will choose the next free port.
+            _localEndPoint = (IPEndPoint)_socket.LocalEndPoint;
+            _options.Port = _localEndPoint.Port;
+
+            _socket.Listen(_options.ConnectionBacklog);
+
+            _logger.Verbose("TCP listener started (Endpoint={0})", _localEndPoint);
+
+            Task.Run(() => AcceptClientConnectionsAsync(cancellationToken), cancellationToken).RunInBackground(_logger);
+
+            return true;
+        }
+        catch (Exception exception)
+        {
+            if (!treatErrorsAsWarning)
+            {
+                throw;
+            }
+
+            _logger.Warning(exception, "Error while starting TCP listener (Endpoint={0})", _localEndPoint);
+            return false;
+        }
+    }
+
+    public void Dispose()
+    {
+        _socket?.Dispose();
+    }
+
+    async Task AcceptClientConnectionsAsync(CancellationToken cancellationToken)
+    {
+        while (!cancellationToken.IsCancellationRequested)
         {
             try
             {
-                var boundIp = _options.BoundInterNetworkAddress;
-                if (_addressFamily == AddressFamily.InterNetworkV6)
+                var clientSocket = await _socket.AcceptAsync(cancellationToken).ConfigureAwait(false);
+                if (clientSocket == null)
                 {
-                    boundIp = _options.BoundInterNetworkV6Address;
+                    continue;
                 }
 
-                _localEndPoint = new IPEndPoint(boundIp, _options.Port);
-
-                _logger.Info("Starting TCP listener (Endpoint={0}, TLS={1})", _localEndPoint, _tlsOptions?.CertificateProvider != null);
-
-                _socket = new CrossPlatformSocket(_addressFamily, ProtocolType.Tcp);
-
-                // Usage of socket options is described here: https://docs.microsoft.com/en-us/dotnet/api/system.net.sockets.socket.setsocketoption?view=netcore-2.2
-                if (_options.ReuseAddress)
-                {
-                    _socket.ReuseAddress = true;
-                }
-
-                if (_options.NoDelay)
-                {
-                    _socket.NoDelay = true;
-                }
-
-                if (_options.LingerState != null)
-                {
-                    _socket.LingerState = _options.LingerState;
-                }
-
-                if (_options.KeepAlive.HasValue)
-                {
-                    _socket.KeepAlive = _options.KeepAlive.Value;
-                }
-
-                if (_options.TcpKeepAliveInterval.HasValue)
-                {
-                    _socket.TcpKeepAliveInterval = _options.TcpKeepAliveInterval.Value;
-                }
-
-                if (_options.TcpKeepAliveRetryCount.HasValue)
-                {
-                    _socket.TcpKeepAliveInterval = _options.TcpKeepAliveRetryCount.Value;
-                }
-
-                if (_options.TcpKeepAliveTime.HasValue)
-                {
-                    _socket.TcpKeepAliveTime = _options.TcpKeepAliveTime.Value;
-                }
-
-                _socket.Bind(_localEndPoint);
-
-                // Get the local endpoint back from the socket. The port may have changed.
-                // This can happen when port 0 is used. Then the OS will choose the next free port.
-                _localEndPoint = (IPEndPoint)_socket.LocalEndPoint;
-                _options.Port = _localEndPoint.Port;
-
-                _socket.Listen(_options.ConnectionBacklog);
-
-                _logger.Verbose("TCP listener started (Endpoint={0})", _localEndPoint);
-
-                Task.Run(() => AcceptClientConnectionsAsync(cancellationToken), cancellationToken).RunInBackground(_logger);
-
-                return true;
+                _ = Task.Factory.StartNew(() => TryHandleClientConnectionAsync(clientSocket), cancellationToken, TaskCreationOptions.PreferFairness, TaskScheduler.Default).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException)
+            {
             }
             catch (Exception exception)
             {
-                if (!treatErrorsAsWarning)
+                if (exception is SocketException socketException)
                 {
-                    throw;
-                }
-
-                _logger.Warning(exception, "Error while starting TCP listener (Endpoint={0})", _localEndPoint);
-                return false;
-            }
-        }
-
-        public void Dispose()
-        {
-            _socket?.Dispose();
-        }
-
-        async Task AcceptClientConnectionsAsync(CancellationToken cancellationToken)
-        {
-            while (!cancellationToken.IsCancellationRequested)
-            {
-                try
-                {
-                    var clientSocket = await _socket.AcceptAsync(cancellationToken).ConfigureAwait(false);
-                    if (clientSocket == null)
+                    if (socketException.SocketErrorCode is SocketError.ConnectionAborted or SocketError.OperationAborted)
                     {
                         continue;
                     }
+                }
 
-                    _ = Task.Factory.StartNew(() => TryHandleClientConnectionAsync(clientSocket), cancellationToken, TaskCreationOptions.PreferFairness, TaskScheduler.Default).ConfigureAwait(false);
-                }
-                catch (OperationCanceledException)
-                {
-                }
-                catch (Exception exception)
-                {
-                    if (exception is SocketException socketException)
-                    {
-                        if (socketException.SocketErrorCode == SocketError.ConnectionAborted ||
-                            socketException.SocketErrorCode == SocketError.OperationAborted)
-                        {
-                            continue;
-                        }
-                    }
-
-                    _logger.Error(exception, "Error while accepting TCP connection (Endpoint={0})", _localEndPoint);
-                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
-                }
+                _logger.Error(exception, "Error while accepting TCP connection (Endpoint={0})", _localEndPoint);
+                await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
             }
         }
-
-        async Task TryHandleClientConnectionAsync(CrossPlatformSocket clientSocket)
-        {
-            Stream stream = null;
-            EndPoint remoteEndPoint = null;
-
-            try
-            {
-                remoteEndPoint = clientSocket.RemoteEndPoint;
-
-                _logger.Verbose("TCP client '{0}' accepted (Local endpoint={1})", remoteEndPoint, _localEndPoint);
-
-                clientSocket.NoDelay = _options.NoDelay;
-                stream = clientSocket.GetStream();
-                var clientCertificate = _tlsOptions?.CertificateProvider?.GetCertificate();
-
-                if (clientCertificate != null)
-                {
-                    if (!clientCertificate.HasPrivateKey)
-                    {
-                        throw new InvalidOperationException("The certificate for TLS encryption must contain the private key.");
-                    }
-
-                    var sslStream = new SslStream(stream, false, _tlsOptions.RemoteCertificateValidationCallback);
-
-                    await sslStream.AuthenticateAsServerAsync(
-                        new SslServerAuthenticationOptions
-                        {
-                            ServerCertificate = clientCertificate,
-                            ClientCertificateRequired = _tlsOptions.ClientCertificateRequired,
-                            EnabledSslProtocols = _tlsOptions.SslProtocol,
-                            CertificateRevocationCheckMode = _tlsOptions.CheckCertificateRevocation ? X509RevocationMode.Online : X509RevocationMode.NoCheck,
-                            EncryptionPolicy = EncryptionPolicy.RequireEncryption,
-                            CipherSuitesPolicy = _tlsOptions.CipherSuitesPolicy
-                        }).ConfigureAwait(false);
-
-                    stream = sslStream;
-
-                    clientCertificate = sslStream.RemoteCertificate as X509Certificate2;
-
-                    if (clientCertificate == null && sslStream.RemoteCertificate != null)
-                    {
-                        clientCertificate = new X509Certificate2(sslStream.RemoteCertificate.Export(X509ContentType.Cert));
-                    }
-                }
-
-                var clientHandler = ClientHandler;
-                if (clientHandler != null)
-                {
-                    var tcpChannel = new MqttTcpChannel(stream, remoteEndPoint, clientCertificate);
-                    var bufferWriter = new MqttBufferWriter(_serverOptions.WriterBufferSize, _serverOptions.WriterBufferSizeMax);
-                    var packetFormatterAdapter = new MqttPacketFormatterAdapter(bufferWriter);
-
-                    using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger))
-                    {
-                        clientAdapter.AllowPacketFragmentation = _options.AllowPacketFragmentation;
-                        await clientHandler(clientAdapter).ConfigureAwait(false);
-                    }
-                }
-            }
-            catch (Exception exception)
-            {
-                if (exception is ObjectDisposedException)
-                {
-                    // It can happen that the listener socket is accessed after the cancellation token is already set and the listener socket is disposed.
-                    return;
-                }
-
-                if (exception is SocketException socketException &&
-                    socketException.SocketErrorCode == SocketError.OperationAborted)
-                {
-                    return;
-                }
-
-                _logger.Error(exception, "Error while handling TCP client connection");
-            }
-            finally
-            {
-                try
-                {
-                    // ReSharper disable once MethodHasAsyncOverload
-                    stream?.Dispose();
-                    clientSocket?.Dispose();
-                }
-                catch (Exception disposeException)
-                {
-                    _logger.Error(disposeException, "Error while cleaning up client connection");
-                }
-            }
-
-            _logger.Verbose("TCP client '{0}' disconnected (Local endpoint={1})", remoteEndPoint, _localEndPoint);
-        }
     }
-}
+
+    async Task TryHandleClientConnectionAsync(CrossPlatformSocket clientSocket)
+    {
+        Stream stream = null;
+        EndPoint remoteEndPoint = null;
+
+        try
+        {
+            remoteEndPoint = clientSocket.RemoteEndPoint;
+
+            _logger.Verbose("TCP client '{0}' accepted (Local endpoint={1})", remoteEndPoint, _localEndPoint);
+
+            clientSocket.NoDelay = _options.NoDelay;
+            stream = clientSocket.GetStream();
+            var clientCertificate = _tlsOptions?.CertificateProvider?.GetCertificate();
+
+            if (clientCertificate != null)
+            {
+                if (!clientCertificate.HasPrivateKey)
+                {
+                    throw new InvalidOperationException("The certificate for TLS encryption must contain the private key.");
+                }
+
+                var sslStream = new SslStream(stream, false, _tlsOptions.RemoteCertificateValidationCallback);
+
+                await sslStream.AuthenticateAsServerAsync(
+                    new SslServerAuthenticationOptions
+                    {
+                        ServerCertificate = clientCertificate,
+                        ClientCertificateRequired = _tlsOptions.ClientCertificateRequired,
+                        EnabledSslProtocols = _tlsOptions.SslProtocol,
+                        CertificateRevocationCheckMode = _tlsOptions.CheckCertificateRevocation ? X509RevocationMode.Online : X509RevocationMode.NoCheck,
+                        EncryptionPolicy = EncryptionPolicy.RequireEncryption,
+                        CipherSuitesPolicy = _tlsOptions.CipherSuitesPolicy
+                    }).ConfigureAwait(false);
+
+                stream = sslStream;
+
+                clientCertificate = sslStream.RemoteCertificate as X509Certificate2;
+
+                if (clientCertificate == null && sslStream.RemoteCertificate != null)
+                {
+                    clientCertificate = new X509Certificate2(sslStream.RemoteCertificate.Export(X509ContentType.Cert));
+                }
+            }
+
+            var clientHandler = ClientHandler;
+            if (clientHandler != null)
+            {
+                var tcpChannel = new MqttTcpChannel(stream, remoteEndPoint, clientCertificate);
+                var bufferWriter = new MqttBufferWriter(_serverOptions.WriterBufferSize, _serverOptions.WriterBufferSizeMax);
+                var packetFormatterAdapter = new MqttPacketFormatterAdapter(bufferWriter);
+
+                using var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger);
+                clientAdapter.AllowPacketFragmentation = _options.AllowPacketFragmentation;
+                await clientHandler(clientAdapter).ConfigureAwait(false);
+            }
+        }
+        catch (Exception exception)
+        {
+            if (exception is ObjectDisposedException)
+            {
+                // It can happen that the listener socket is accessed after the cancellation token is already set and the listener socket is disposed.
+                return;
+            }
+
+            if (exception is SocketException socketException &&
+                socketException.SocketErrorCode == SocketError.OperationAborted)
+            {
+                return;
+            }
+
+            _logger.Error(exception, "Error while handling TCP client connection");
+        }
+        finally
+        {
+            try
+            {
+                if (stream != null)
+                {
+                    await stream.DisposeAsync().ConfigureAwait(false);
+                }
+
+                clientSocket?.Dispose();
+            }
+            catch (Exception disposeException)
+            {
+                _logger.Error(disposeException, "Error while cleaning up client connection");
+            }
+        }
+
+        _logger.Verbose("TCP client '{0}' disconnected (Local endpoint={1})", remoteEndPoint, _localEndPoint);
+    }
+}

Source/MQTTnet.Server/Internal/CheckSubscriptionsResult.cs

@@ -4,18 +4,17 @@
 
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class CheckSubscriptionsResult
 {
-    public sealed class CheckSubscriptionsResult
-    {
-        public static CheckSubscriptionsResult NotSubscribed { get; } = new CheckSubscriptionsResult();
+    public static CheckSubscriptionsResult NotSubscribed { get; } = new CheckSubscriptionsResult();
 
-        public bool IsSubscribed { get; set; }
+    public bool IsSubscribed { get; set; }
 
-        public bool RetainAsPublished { get; set; }
-        
-        public List<uint> SubscriptionIdentifiers { get; set; }
-        
-        public MqttQualityOfServiceLevel QualityOfServiceLevel { get; set; }
-    }
-}
+    public bool RetainAsPublished { get; set; }
+
+    public List<uint> SubscriptionIdentifiers { get; set; }
+
+    public MqttQualityOfServiceLevel QualityOfServiceLevel { get; set; }
+}

Source/MQTTnet.Server/Internal/DispatchApplicationMessageResult.cs

@@ -4,24 +4,23 @@
 
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class DispatchApplicationMessageResult
 {
-    public sealed class DispatchApplicationMessageResult
+    public DispatchApplicationMessageResult(int reasonCode, bool closeConnection, string reasonString, List<MqttUserProperty> userProperties)
     {
-        public DispatchApplicationMessageResult(int reasonCode, bool closeConnection, string reasonString, List<MqttUserProperty> userProperties)
-        {
-            ReasonCode = reasonCode;
-            CloseConnection = closeConnection;
-            ReasonString = reasonString;
-            UserProperties = userProperties;
-        }
-
-        public bool CloseConnection { get; }
-
-        public int ReasonCode { get; }
-
-        public string ReasonString { get; }
-
-        public List<MqttUserProperty> UserProperties { get; }
+        ReasonCode = reasonCode;
+        CloseConnection = closeConnection;
+        ReasonString = reasonString;
+        UserProperties = userProperties;
     }
+
+    public bool CloseConnection { get; }
+
+    public int ReasonCode { get; }
+
+    public string ReasonString { get; }
+
+    public List<MqttUserProperty> UserProperties { get; }
 }

Source/MQTTnet.Server/Internal/EnqueueDataPacketResult.cs

@@ -2,11 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public enum EnqueueDataPacketResult
 {
-    public enum EnqueueDataPacketResult
-    {
-        Enqueued,
-        Dropped
-    }
+    Enqueued,
+    Dropped
 }

Source/MQTTnet.Server/Internal/Formatter/MqttUnsubAckPacketFactory.cs

@@ -4,24 +4,23 @@
 
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server.Internal.Formatter
+namespace MQTTnet.Server.Internal.Formatter;
+
+public static class MqttUnsubAckPacketFactory
 {
-    public static class MqttUnsubAckPacketFactory
+    public static MqttUnsubAckPacket Create(MqttUnsubscribePacket unsubscribePacket, UnsubscribeResult unsubscribeResult)
     {
-        public static MqttUnsubAckPacket Create(MqttUnsubscribePacket unsubscribePacket, UnsubscribeResult unsubscribeResult)
+        ArgumentNullException.ThrowIfNull(unsubscribePacket);
+        ArgumentNullException.ThrowIfNull(unsubscribeResult);
+
+        var unsubAckPacket = new MqttUnsubAckPacket
         {
-            ArgumentNullException.ThrowIfNull(unsubscribePacket);
-            ArgumentNullException.ThrowIfNull(unsubscribeResult);
+            PacketIdentifier = unsubscribePacket.PacketIdentifier
+        };
 
-            var unsubAckPacket = new MqttUnsubAckPacket
-            {
-                PacketIdentifier = unsubscribePacket.PacketIdentifier
-            };
+        // MQTTv5.0.0 only.
+        unsubAckPacket.ReasonCodes = unsubscribeResult.ReasonCodes;
 
-            // MQTTv5.0.0 only.
-            unsubAckPacket.ReasonCodes = unsubscribeResult.ReasonCodes;
-
-            return unsubAckPacket;
-        }
+        return unsubAckPacket;
     }
 }

Source/MQTTnet.Server/Internal/ISubscriptionChangedNotification.cs

@@ -1,9 +1,8 @@
-namespace MQTTnet.Server.Internal
-{
-    public interface ISubscriptionChangedNotification
-    {
-        void OnSubscriptionsAdded(MqttSession clientSession, List<string> subscriptionsTopics);
+namespace MQTTnet.Server.Internal;
 
-        void OnSubscriptionsRemoved(MqttSession clientSession, List<string> subscriptionTopics);
-    }
+public interface ISubscriptionChangedNotification
+{
+    void OnSubscriptionsAdded(MqttSession clientSession, List<string> subscriptionsTopics);
+
+    void OnSubscriptionsRemoved(MqttSession clientSession, List<string> subscriptionTopics);
 }

Source/MQTTnet.Server/Internal/MqttClientSessionsManager.cs

@@ -439,10 +439,8 @@ public sealed class MqttClientSessionsManager : ISubscriptionChangedNotification
                 }
             }
 
-            using (var timeout = new CancellationTokenSource(_options.DefaultCommunicationTimeout))
-            {
-                await channelAdapter.DisconnectAsync(timeout.Token).ConfigureAwait(false);
-            }
+            using var timeout = new CancellationTokenSource(_options.DefaultCommunicationTimeout);
+            await channelAdapter.DisconnectAsync(timeout.Token).ConfigureAwait(false);
         }
     }
 
@@ -673,14 +671,12 @@ public sealed class MqttClientSessionsManager : ISubscriptionChangedNotification
     {
         try
         {
-            using (var timeoutToken = new CancellationTokenSource(_options.DefaultCommunicationTimeout))
-            using (var effectiveCancellationToken = CancellationTokenSource.CreateLinkedTokenSource(timeoutToken.Token, cancellationToken))
+            using var timeoutToken = new CancellationTokenSource(_options.DefaultCommunicationTimeout);
+            using var effectiveCancellationToken = CancellationTokenSource.CreateLinkedTokenSource(timeoutToken.Token, cancellationToken);
+            var firstPacket = await channelAdapter.ReceivePacketAsync(effectiveCancellationToken.Token).ConfigureAwait(false);
+            if (firstPacket is MqttConnectPacket connectPacket)
             {
-                var firstPacket = await channelAdapter.ReceivePacketAsync(effectiveCancellationToken.Token).ConfigureAwait(false);
-                if (firstPacket is MqttConnectPacket connectPacket)
-                {
-                    return connectPacket;
-                }
+                return connectPacket;
             }
         }
         catch (OperationCanceledException)

Source/MQTTnet.Server/Internal/MqttClientStatistics.cs

@@ -4,101 +4,100 @@
 
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttClientStatistics
 {
-    public sealed class MqttClientStatistics
+    Statistics _statistics = new Statistics     // mutable struct, don't make readonly!
     {
-        Statistics _statistics = new Statistics     // mutable struct, don't make readonly!
+        // Start with 1 because the CONNACK packet is not counted here.
+        _receivedPacketsCount = 1,
+
+        // Start with 1 because the CONNECT packet is not counted here.
+        _sentPacketsCount = 1
+    };
+
+    public MqttClientStatistics()
+    {
+        ConnectedTimestamp = DateTime.UtcNow;
+
+        LastPacketReceivedTimestamp = ConnectedTimestamp;
+        LastPacketSentTimestamp = ConnectedTimestamp;
+
+        LastNonKeepAlivePacketReceivedTimestamp = ConnectedTimestamp;
+    }
+
+    public DateTime ConnectedTimestamp { get; }
+    public DateTime LastNonKeepAlivePacketReceivedTimestamp { get; private set; }
+
+    /// <summary>
+    ///     Timestamp of the last package that has been sent to the client ("received" from the client's perspective)
+    /// </summary>
+    public DateTime LastPacketReceivedTimestamp { get; private set; }
+
+    /// <summary>
+    ///     Timestamp of the last package that has been received from the client ("sent" from the client's perspective)
+    /// </summary>
+    public DateTime LastPacketSentTimestamp { get; private set; }
+
+    public long SentApplicationMessagesCount => Volatile.Read(ref _statistics._sentApplicationMessagesCount);
+
+    public long ReceivedApplicationMessagesCount => Volatile.Read(ref _statistics._receivedApplicationMessagesCount);
+
+    public long SentPacketsCount => Volatile.Read(ref _statistics._sentPacketsCount);
+
+    public long ReceivedPacketsCount => Volatile.Read(ref _statistics._receivedPacketsCount);
+
+    public void HandleReceivedPacket(MqttPacket packet)
+    {
+        ArgumentNullException.ThrowIfNull(packet);
+
+        // This class is tracking all values from Clients perspective!
+        LastPacketSentTimestamp = DateTime.UtcNow;
+
+        Interlocked.Increment(ref _statistics._sentPacketsCount);
+
+        if (packet is MqttPublishPacket)
         {
-            // Start with 1 because the CONNACK packet is not counted here.
-            _receivedPacketsCount = 1,
-
-            // Start with 1 because the CONNECT packet is not counted here.
-            _sentPacketsCount = 1
-        };
-
-        public MqttClientStatistics()
-        {
-            ConnectedTimestamp = DateTime.UtcNow;
-
-            LastPacketReceivedTimestamp = ConnectedTimestamp;
-            LastPacketSentTimestamp = ConnectedTimestamp;
-
-            LastNonKeepAlivePacketReceivedTimestamp = ConnectedTimestamp;
+            Interlocked.Increment(ref _statistics._sentApplicationMessagesCount);
         }
 
-        public DateTime ConnectedTimestamp { get; }
-        public DateTime LastNonKeepAlivePacketReceivedTimestamp { get; private set; }
-
-        /// <summary>
-        ///     Timestamp of the last package that has been sent to the client ("received" from the client's perspective)
-        /// </summary>
-        public DateTime LastPacketReceivedTimestamp { get; private set; }
-
-        /// <summary>
-        ///     Timestamp of the last package that has been received from the client ("sent" from the client's perspective)
-        /// </summary>
-        public DateTime LastPacketSentTimestamp { get; private set; }
-
-        public long SentApplicationMessagesCount => Volatile.Read(ref _statistics._sentApplicationMessagesCount);
-
-        public long ReceivedApplicationMessagesCount => Volatile.Read(ref _statistics._receivedApplicationMessagesCount);
-
-        public long SentPacketsCount => Volatile.Read(ref _statistics._sentPacketsCount);
-
-        public long ReceivedPacketsCount => Volatile.Read(ref _statistics._receivedPacketsCount);
-
-        public void HandleReceivedPacket(MqttPacket packet)
+        if (!(packet is MqttPingReqPacket || packet is MqttPingRespPacket))
         {
-            ArgumentNullException.ThrowIfNull(packet);
-
-            // This class is tracking all values from Clients perspective!
-            LastPacketSentTimestamp = DateTime.UtcNow;
-
-            Interlocked.Increment(ref _statistics._sentPacketsCount);
-
-            if (packet is MqttPublishPacket)
-            {
-                Interlocked.Increment(ref _statistics._sentApplicationMessagesCount);
-            }
-
-            if (!(packet is MqttPingReqPacket || packet is MqttPingRespPacket))
-            {
-                LastNonKeepAlivePacketReceivedTimestamp = LastPacketReceivedTimestamp;
-            }
+            LastNonKeepAlivePacketReceivedTimestamp = LastPacketReceivedTimestamp;
         }
-        public void ResetStatistics() => _statistics.Reset();
+    }
+    public void ResetStatistics() => _statistics.Reset();
 
-        public void HandleSentPacket(MqttPacket packet)
+    public void HandleSentPacket(MqttPacket packet)
+    {
+        ArgumentNullException.ThrowIfNull(packet);
+
+        // This class is tracking all values from Clients perspective!
+        LastPacketReceivedTimestamp = DateTime.UtcNow;
+
+        Interlocked.Increment(ref _statistics._receivedPacketsCount);
+
+        if (packet is MqttPublishPacket)
         {
-            ArgumentNullException.ThrowIfNull(packet);
-
-            // This class is tracking all values from Clients perspective!
-            LastPacketReceivedTimestamp = DateTime.UtcNow;
-
-            Interlocked.Increment(ref _statistics._receivedPacketsCount);
-
-            if (packet is MqttPublishPacket)
-            {
-                Interlocked.Increment(ref _statistics._receivedApplicationMessagesCount);
-            }
+            Interlocked.Increment(ref _statistics._receivedApplicationMessagesCount);
         }
+    }
 
-        struct Statistics
+    struct Statistics
+    {
+        public long _receivedPacketsCount;
+        public long _sentPacketsCount;
+
+        public long _receivedApplicationMessagesCount;
+        public long _sentApplicationMessagesCount;
+
+        public void Reset()
         {
-            public long _receivedPacketsCount;
-            public long _sentPacketsCount;
-
-            public long _receivedApplicationMessagesCount;
-            public long _sentApplicationMessagesCount;
-
-            public void Reset()
-            {
-                Volatile.Write(ref _receivedPacketsCount, 0);
-                Volatile.Write(ref _sentPacketsCount, 0);
-                Volatile.Write(ref _receivedApplicationMessagesCount, 0);
-                Volatile.Write(ref _sentApplicationMessagesCount, 0);
-            }
+            Volatile.Write(ref _receivedPacketsCount, 0);
+            Volatile.Write(ref _sentPacketsCount, 0);
+            Volatile.Write(ref _receivedApplicationMessagesCount, 0);
+            Volatile.Write(ref _sentApplicationMessagesCount, 0);
         }
     }
 }

Source/MQTTnet.Server/Internal/MqttClientSubscriptionsManager.cs

@@ -5,180 +5,237 @@
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttClientSubscriptionsManager : IDisposable
 {
-    public sealed class MqttClientSubscriptionsManager : IDisposable
+    static readonly List<uint> EmptySubscriptionIdentifiers = new List<uint>();
+
+    readonly MqttServerEventContainer _eventContainer;
+    readonly Dictionary<ulong, HashSet<MqttSubscription>> _noWildcardSubscriptionsByTopicHash = new Dictionary<ulong, HashSet<MqttSubscription>>();
+    readonly MqttRetainedMessagesManager _retainedMessagesManager;
+
+    readonly MqttSession _session;
+
+    // Callback to maintain list of subscriber clients
+    readonly ISubscriptionChangedNotification _subscriptionChangedNotification;
+
+    // Subscriptions are stored in various dictionaries and use a "topic hash"; see the MqttSubscription object for a detailed explanation.
+    // The additional lock is important to coordinate complex update logic with multiple steps, checks and interceptors.
+    readonly Dictionary<string, MqttSubscription> _subscriptions = new Dictionary<string, MqttSubscription>();
+
+    // Use subscription lock to maintain consistency across subscriptions and topic hash dictionaries
+    readonly ReaderWriterLockSlim _subscriptionsLock = new ReaderWriterLockSlim();
+    readonly Dictionary<ulong, TopicHashMaskSubscriptions> _wildcardSubscriptionsByTopicHash = new Dictionary<ulong, TopicHashMaskSubscriptions>();
+
+    public MqttClientSubscriptionsManager(
+        MqttSession session,
+        MqttServerEventContainer eventContainer,
+        MqttRetainedMessagesManager retainedMessagesManager,
+        ISubscriptionChangedNotification subscriptionChangedNotification)
     {
-        static readonly List<uint> EmptySubscriptionIdentifiers = new List<uint>();
+        _session = session ?? throw new ArgumentNullException(nameof(session));
+        _eventContainer = eventContainer ?? throw new ArgumentNullException(nameof(eventContainer));
+        _retainedMessagesManager = retainedMessagesManager ?? throw new ArgumentNullException(nameof(retainedMessagesManager));
+        _subscriptionChangedNotification = subscriptionChangedNotification;
+    }
 
-        readonly MqttServerEventContainer _eventContainer;
-        readonly Dictionary<ulong, HashSet<MqttSubscription>> _noWildcardSubscriptionsByTopicHash = new Dictionary<ulong, HashSet<MqttSubscription>>();
-        readonly MqttRetainedMessagesManager _retainedMessagesManager;
+    public CheckSubscriptionsResult CheckSubscriptions(string topic, ulong topicHash, MqttQualityOfServiceLevel qualityOfServiceLevel, string senderId)
+    {
+        var possibleSubscriptions = new List<MqttSubscription>();
 
-        readonly MqttSession _session;
-
-        // Callback to maintain list of subscriber clients
-        readonly ISubscriptionChangedNotification _subscriptionChangedNotification;
-
-        // Subscriptions are stored in various dictionaries and use a "topic hash"; see the MqttSubscription object for a detailed explanation.
-        // The additional lock is important to coordinate complex update logic with multiple steps, checks and interceptors.
-        readonly Dictionary<string, MqttSubscription> _subscriptions = new Dictionary<string, MqttSubscription>();
-
-        // Use subscription lock to maintain consistency across subscriptions and topic hash dictionaries
-        readonly ReaderWriterLockSlim _subscriptionsLock = new ReaderWriterLockSlim();
-        readonly Dictionary<ulong, TopicHashMaskSubscriptions> _wildcardSubscriptionsByTopicHash = new Dictionary<ulong, TopicHashMaskSubscriptions>();
-
-        public MqttClientSubscriptionsManager(
-            MqttSession session,
-            MqttServerEventContainer eventContainer,
-            MqttRetainedMessagesManager retainedMessagesManager,
-            ISubscriptionChangedNotification subscriptionChangedNotification)
+        // Check for possible subscriptions. They might have collisions but this is fine.
+        _subscriptionsLock.EnterReadLock();
+        try
         {
-            _session = session ?? throw new ArgumentNullException(nameof(session));
-            _eventContainer = eventContainer ?? throw new ArgumentNullException(nameof(eventContainer));
-            _retainedMessagesManager = retainedMessagesManager ?? throw new ArgumentNullException(nameof(retainedMessagesManager));
-            _subscriptionChangedNotification = subscriptionChangedNotification;
-        }
-
-        public CheckSubscriptionsResult CheckSubscriptions(string topic, ulong topicHash, MqttQualityOfServiceLevel qualityOfServiceLevel, string senderId)
-        {
-            var possibleSubscriptions = new List<MqttSubscription>();
-
-            // Check for possible subscriptions. They might have collisions but this is fine.
-            _subscriptionsLock.EnterReadLock();
-            try
+            if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var noWildcardSubscriptions))
             {
-                if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var noWildcardSubscriptions))
-                {
-                    possibleSubscriptions.AddRange(noWildcardSubscriptions);
-                }
+                possibleSubscriptions.AddRange(noWildcardSubscriptions);
+            }
 
-                foreach (var wcs in _wildcardSubscriptionsByTopicHash)
+            foreach (var wcs in _wildcardSubscriptionsByTopicHash)
+            {
+                var subscriptionHash = wcs.Key;
+                var subscriptionsByHashMask = wcs.Value.SubscriptionsByHashMask;
+                foreach (var shm in subscriptionsByHashMask)
                 {
-                    var subscriptionHash = wcs.Key;
-                    var subscriptionsByHashMask = wcs.Value.SubscriptionsByHashMask;
-                    foreach (var shm in subscriptionsByHashMask)
+                    var subscriptionHashMask = shm.Key;
+                    if ((topicHash & subscriptionHashMask) == subscriptionHash)
                     {
-                        var subscriptionHashMask = shm.Key;
-                        if ((topicHash & subscriptionHashMask) == subscriptionHash)
-                        {
-                            var subscriptions = shm.Value;
-                            possibleSubscriptions.AddRange(subscriptions);
-                        }
+                        var subscriptions = shm.Value;
+                        possibleSubscriptions.AddRange(subscriptions);
                     }
                 }
             }
-            finally
-            {
-                _subscriptionsLock.ExitReadLock();
-            }
-
-            // The pre check has evaluated that nothing is subscribed.
-            // If there were some possible candidates they get checked below
-            // again to avoid collisions.
-            if (possibleSubscriptions.Count == 0)
-            {
-                return CheckSubscriptionsResult.NotSubscribed;
-            }
-
-            var senderIsReceiver = string.Equals(senderId, _session.Id);
-            var maxQoSLevel = -1; // Not subscribed.
-
-            HashSet<uint> subscriptionIdentifiers = null;
-            var retainAsPublished = false;
-
-            foreach (var subscription in possibleSubscriptions)
-            {
-                if (subscription.NoLocal && senderIsReceiver)
-                {
-                    // This is a MQTTv5 feature!
-                    continue;
-                }
-
-                if (MqttTopicFilterComparer.Compare(topic, subscription.Topic) != MqttTopicFilterCompareResult.IsMatch)
-                {
-                    continue;
-                }
-
-                if (subscription.RetainAsPublished)
-                {
-                    // This is a MQTTv5 feature!
-                    retainAsPublished = true;
-                }
-
-                if ((int)subscription.GrantedQualityOfServiceLevel > maxQoSLevel)
-                {
-                    maxQoSLevel = (int)subscription.GrantedQualityOfServiceLevel;
-                }
-
-                if (subscription.Identifier > 0)
-                {
-                    if (subscriptionIdentifiers == null)
-                    {
-                        subscriptionIdentifiers = new HashSet<uint>();
-                    }
-
-                    subscriptionIdentifiers.Add(subscription.Identifier);
-                }
-            }
-
-            if (maxQoSLevel == -1)
-            {
-                return CheckSubscriptionsResult.NotSubscribed;
-            }
-
-            var result = new CheckSubscriptionsResult
-            {
-                IsSubscribed = true,
-                RetainAsPublished = retainAsPublished,
-                SubscriptionIdentifiers = subscriptionIdentifiers?.ToList() ?? EmptySubscriptionIdentifiers,
-
-                // Start with the same QoS as the publisher.
-                QualityOfServiceLevel = qualityOfServiceLevel
-            };
-
-            // Now downgrade if required.
-            //
-            // If a subscribing Client has been granted maximum QoS 1 for a particular Topic Filter, then a QoS 0 Application Message matching the filter is delivered
-            // to the Client at QoS 0. This means that at most one copy of the message is received by the Client. On the other hand, a QoS 2 Message published to
-            // the same topic is downgraded by the Server to QoS 1 for delivery to the Client, so that Client might receive duplicate copies of the Message.
-
-            // Subscribing to a Topic Filter at QoS 2 is equivalent to saying "I would like to receive Messages matching this filter at the QoS with which they were published".
-            // This means a publisher is responsible for determining the maximum QoS a Message can be delivered at, but a subscriber is able to require that the Server
-            // downgrades the QoS to one more suitable for its usage.
-            if (maxQoSLevel < (int)qualityOfServiceLevel)
-            {
-                result.QualityOfServiceLevel = (MqttQualityOfServiceLevel)maxQoSLevel;
-            }
-
-            return result;
+        }
+        finally
+        {
+            _subscriptionsLock.ExitReadLock();
         }
 
-        public void Dispose()
+        // The pre check has evaluated that nothing is subscribed.
+        // If there were some possible candidates they get checked below
+        // again to avoid collisions.
+        if (possibleSubscriptions.Count == 0)
         {
-            _subscriptionsLock?.Dispose();
+            return CheckSubscriptionsResult.NotSubscribed;
         }
 
-        public async Task<SubscribeResult> Subscribe(MqttSubscribePacket subscribePacket, CancellationToken cancellationToken)
+        var senderIsReceiver = string.Equals(senderId, _session.Id);
+        var maxQoSLevel = -1; // Not subscribed.
+
+        HashSet<uint> subscriptionIdentifiers = null;
+        var retainAsPublished = false;
+
+        foreach (var subscription in possibleSubscriptions)
         {
-            ArgumentNullException.ThrowIfNull(subscribePacket);
-
-            var retainedApplicationMessages = await _retainedMessagesManager.GetMessages().ConfigureAwait(false);
-            var result = new SubscribeResult(subscribePacket.TopicFilters.Count);
-
-            var addedSubscriptions = new List<string>();
-            var finalTopicFilters = new List<MqttTopicFilter>();
-
-            // The topic filters are order by its QoS so that the higher QoS will win over a
-            // lower one.
-            foreach (var topicFilterItem in subscribePacket.TopicFilters.OrderByDescending(f => f.QualityOfServiceLevel))
+            if (subscription.NoLocal && senderIsReceiver)
             {
-                var interceptorEventArgs = await InterceptSubscribe(topicFilterItem, subscribePacket.UserProperties, cancellationToken).ConfigureAwait(false);
-                var topicFilter = interceptorEventArgs.TopicFilter;
-                var processSubscription = interceptorEventArgs.ProcessSubscription && interceptorEventArgs.Response.ReasonCode <= MqttSubscribeReasonCode.GrantedQoS2;
+                // This is a MQTTv5 feature!
+                continue;
+            }
+
+            if (MqttTopicFilterComparer.Compare(topic, subscription.Topic) != MqttTopicFilterCompareResult.IsMatch)
+            {
+                continue;
+            }
+
+            if (subscription.RetainAsPublished)
+            {
+                // This is a MQTTv5 feature!
+                retainAsPublished = true;
+            }
+
+            if ((int)subscription.GrantedQualityOfServiceLevel > maxQoSLevel)
+            {
+                maxQoSLevel = (int)subscription.GrantedQualityOfServiceLevel;
+            }
+
+            if (subscription.Identifier > 0)
+            {
+                if (subscriptionIdentifiers == null)
+                {
+                    subscriptionIdentifiers = new HashSet<uint>();
+                }
+
+                subscriptionIdentifiers.Add(subscription.Identifier);
+            }
+        }
+
+        if (maxQoSLevel == -1)
+        {
+            return CheckSubscriptionsResult.NotSubscribed;
+        }
+
+        var result = new CheckSubscriptionsResult
+        {
+            IsSubscribed = true,
+            RetainAsPublished = retainAsPublished,
+            SubscriptionIdentifiers = subscriptionIdentifiers?.ToList() ?? EmptySubscriptionIdentifiers,
+
+            // Start with the same QoS as the publisher.
+            QualityOfServiceLevel = qualityOfServiceLevel
+        };
+
+        // Now downgrade if required.
+        //
+        // If a subscribing Client has been granted maximum QoS 1 for a particular Topic Filter, then a QoS 0 Application Message matching the filter is delivered
+        // to the Client at QoS 0. This means that at most one copy of the message is received by the Client. On the other hand, a QoS 2 Message published to
+        // the same topic is downgraded by the Server to QoS 1 for delivery to the Client, so that Client might receive duplicate copies of the Message.
+
+        // Subscribing to a Topic Filter at QoS 2 is equivalent to saying "I would like to receive Messages matching this filter at the QoS with which they were published".
+        // This means a publisher is responsible for determining the maximum QoS a Message can be delivered at, but a subscriber is able to require that the Server
+        // downgrades the QoS to one more suitable for its usage.
+        if (maxQoSLevel < (int)qualityOfServiceLevel)
+        {
+            result.QualityOfServiceLevel = (MqttQualityOfServiceLevel)maxQoSLevel;
+        }
+
+        return result;
+    }
+
+    public void Dispose()
+    {
+        _subscriptionsLock?.Dispose();
+    }
+
+    public async Task<SubscribeResult> Subscribe(MqttSubscribePacket subscribePacket, CancellationToken cancellationToken)
+    {
+        ArgumentNullException.ThrowIfNull(subscribePacket);
+
+        var retainedApplicationMessages = await _retainedMessagesManager.GetMessages().ConfigureAwait(false);
+        var result = new SubscribeResult(subscribePacket.TopicFilters.Count);
+
+        var addedSubscriptions = new List<string>();
+        var finalTopicFilters = new List<MqttTopicFilter>();
+
+        // The topic filters are order by its QoS so that the higher QoS will win over a
+        // lower one.
+        foreach (var topicFilterItem in subscribePacket.TopicFilters.OrderByDescending(f => f.QualityOfServiceLevel))
+        {
+            var interceptorEventArgs = await InterceptSubscribe(topicFilterItem, subscribePacket.UserProperties, cancellationToken).ConfigureAwait(false);
+            var topicFilter = interceptorEventArgs.TopicFilter;
+            var processSubscription = interceptorEventArgs.ProcessSubscription && interceptorEventArgs.Response.ReasonCode <= MqttSubscribeReasonCode.GrantedQoS2;
+
+            result.UserProperties = interceptorEventArgs.UserProperties;
+            result.ReasonString = interceptorEventArgs.ReasonString;
+            result.ReasonCodes.Add(interceptorEventArgs.Response.ReasonCode);
+
+            if (interceptorEventArgs.CloseConnection)
+            {
+                // When any of the interceptor calls leads to a connection close the connection
+                // must be closed. So do not revert to false!
+                result.CloseConnection = true;
+            }
+
+            if (!processSubscription || string.IsNullOrEmpty(topicFilter.Topic))
+            {
+                continue;
+            }
+
+            var createSubscriptionResult = CreateSubscription(topicFilter, subscribePacket.SubscriptionIdentifier, interceptorEventArgs.Response.ReasonCode);
+
+            addedSubscriptions.Add(topicFilter.Topic);
+            finalTopicFilters.Add(topicFilter);
+
+            FilterRetainedApplicationMessages(retainedApplicationMessages, createSubscriptionResult, result);
+        }
+
+        // This call will add the new subscription to the internal storage.
+        // So the event _ClientSubscribedTopicEvent_ must be called afterwards.
+        _subscriptionChangedNotification?.OnSubscriptionsAdded(_session, addedSubscriptions);
+
+        if (_eventContainer.ClientSubscribedTopicEvent.HasHandlers)
+        {
+            foreach (var finalTopicFilter in finalTopicFilters)
+            {
+                var eventArgs = new ClientSubscribedTopicEventArgs(_session.Id, _session.UserName, finalTopicFilter, _session.Items);
+                await _eventContainer.ClientSubscribedTopicEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
+            }
+        }
+
+        return result;
+    }
+
+    public async Task<UnsubscribeResult> Unsubscribe(MqttUnsubscribePacket unsubscribePacket, CancellationToken cancellationToken)
+    {
+        ArgumentNullException.ThrowIfNull(unsubscribePacket);
+
+        var result = new UnsubscribeResult();
+
+        var removedSubscriptions = new List<string>();
+
+        _subscriptionsLock.EnterWriteLock();
+        try
+        {
+            foreach (var topicFilter in unsubscribePacket.TopicFilters)
+            {
+                _subscriptions.TryGetValue(topicFilter, out var existingSubscription);
+
+                var interceptorEventArgs = await InterceptUnsubscribe(topicFilter, existingSubscription, unsubscribePacket.UserProperties, cancellationToken).ConfigureAwait(false);
+                var acceptUnsubscription = interceptorEventArgs.Response.ReasonCode == MqttUnsubscribeReasonCode.Success;
 
                 result.UserProperties = interceptorEventArgs.UserProperties;
-                result.ReasonString = interceptorEventArgs.ReasonString;
                 result.ReasonCodes.Add(interceptorEventArgs.Response.ReasonCode);
 
                 if (interceptorEventArgs.CloseConnection)
@@ -188,329 +245,271 @@ namespace MQTTnet.Server.Internal
                     result.CloseConnection = true;
                 }
 
-                if (!processSubscription || string.IsNullOrEmpty(topicFilter.Topic))
+                if (!acceptUnsubscription)
                 {
                     continue;
                 }
 
-                var createSubscriptionResult = CreateSubscription(topicFilter, subscribePacket.SubscriptionIdentifier, interceptorEventArgs.Response.ReasonCode);
-
-                addedSubscriptions.Add(topicFilter.Topic);
-                finalTopicFilters.Add(topicFilter);
-
-                FilterRetainedApplicationMessages(retainedApplicationMessages, createSubscriptionResult, result);
-            }
-
-            // This call will add the new subscription to the internal storage.
-            // So the event _ClientSubscribedTopicEvent_ must be called afterwards.
-            _subscriptionChangedNotification?.OnSubscriptionsAdded(_session, addedSubscriptions);
-
-            if (_eventContainer.ClientSubscribedTopicEvent.HasHandlers)
-            {
-                foreach (var finalTopicFilter in finalTopicFilters)
+                if (interceptorEventArgs.ProcessUnsubscription)
                 {
-                    var eventArgs = new ClientSubscribedTopicEventArgs(_session.Id, _session.UserName, finalTopicFilter, _session.Items);
-                    await _eventContainer.ClientSubscribedTopicEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
-                }
-            }
+                    _subscriptions.Remove(topicFilter);
 
-            return result;
-        }
-
-        public async Task<UnsubscribeResult> Unsubscribe(MqttUnsubscribePacket unsubscribePacket, CancellationToken cancellationToken)
-        {
-            ArgumentNullException.ThrowIfNull(unsubscribePacket);
-
-            var result = new UnsubscribeResult();
-
-            var removedSubscriptions = new List<string>();
-
-            _subscriptionsLock.EnterWriteLock();
-            try
-            {
-                foreach (var topicFilter in unsubscribePacket.TopicFilters)
-                {
-                    _subscriptions.TryGetValue(topicFilter, out var existingSubscription);
-
-                    var interceptorEventArgs = await InterceptUnsubscribe(topicFilter, existingSubscription, unsubscribePacket.UserProperties, cancellationToken).ConfigureAwait(false);
-                    var acceptUnsubscription = interceptorEventArgs.Response.ReasonCode == MqttUnsubscribeReasonCode.Success;
-
-                    result.UserProperties = interceptorEventArgs.UserProperties;
-                    result.ReasonCodes.Add(interceptorEventArgs.Response.ReasonCode);
-
-                    if (interceptorEventArgs.CloseConnection)
+                    // must remove subscription object from topic hash dictionary also
+                    if (existingSubscription != null)
                     {
-                        // When any of the interceptor calls leads to a connection close the connection
-                        // must be closed. So do not revert to false!
-                        result.CloseConnection = true;
-                    }
+                        var topicHash = existingSubscription.TopicHash;
 
-                    if (!acceptUnsubscription)
-                    {
-                        continue;
-                    }
-
-                    if (interceptorEventArgs.ProcessUnsubscription)
-                    {
-                        _subscriptions.Remove(topicFilter);
-
-                        // must remove subscription object from topic hash dictionary also
-                        if (existingSubscription != null)
+                        if (existingSubscription.TopicHasWildcard)
                         {
-                            var topicHash = existingSubscription.TopicHash;
-
-                            if (existingSubscription.TopicHasWildcard)
+                            if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                             {
-                                if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
+                                subscriptions.RemoveSubscription(existingSubscription);
+                                if (subscriptions.SubscriptionsByHashMask.Count == 0)
                                 {
-                                    subscriptions.RemoveSubscription(existingSubscription);
-                                    if (subscriptions.SubscriptionsByHashMask.Count == 0)
-                                    {
-                                        _wildcardSubscriptionsByTopicHash.Remove(topicHash);
-                                    }
-                                }
-                            }
-                            else
-                            {
-                                if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
-                                {
-                                    subscriptions.Remove(existingSubscription);
-                                    if (subscriptions.Count == 0)
-                                    {
-                                        _noWildcardSubscriptionsByTopicHash.Remove(topicHash);
-                                    }
+                                    _wildcardSubscriptionsByTopicHash.Remove(topicHash);
+                                }
+                            }
+                        }
+                        else
+                        {
+                            if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
+                            {
+                                subscriptions.Remove(existingSubscription);
+                                if (subscriptions.Count == 0)
+                                {
+                                    _noWildcardSubscriptionsByTopicHash.Remove(topicHash);
                                 }
                             }
                         }
-
-                        removedSubscriptions.Add(topicFilter);
                     }
+
+                    removedSubscriptions.Add(topicFilter);
                 }
             }
-            finally
-            {
-                _subscriptionsLock.ExitWriteLock();
-                _subscriptionChangedNotification?.OnSubscriptionsRemoved(_session, removedSubscriptions);
-            }
-
-            if (_eventContainer.ClientUnsubscribedTopicEvent.HasHandlers)
-            {
-                foreach (var topicFilter in unsubscribePacket.TopicFilters)
-                {
-                    var eventArgs = new ClientUnsubscribedTopicEventArgs(_session.Id, _session.UserName, topicFilter, _session.Items);
-                    await _eventContainer.ClientUnsubscribedTopicEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
-                }
-            }
-
-            return result;
+        }
+        finally
+        {
+            _subscriptionsLock.ExitWriteLock();
+            _subscriptionChangedNotification?.OnSubscriptionsRemoved(_session, removedSubscriptions);
         }
 
-        CreateSubscriptionResult CreateSubscription(MqttTopicFilter topicFilter, uint subscriptionIdentifier, MqttSubscribeReasonCode reasonCode)
+        if (_eventContainer.ClientUnsubscribedTopicEvent.HasHandlers)
         {
-            MqttQualityOfServiceLevel grantedQualityOfServiceLevel;
-
-            if (reasonCode == MqttSubscribeReasonCode.GrantedQoS0)
+            foreach (var topicFilter in unsubscribePacket.TopicFilters)
             {
-                grantedQualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
+                var eventArgs = new ClientUnsubscribedTopicEventArgs(_session.Id, _session.UserName, topicFilter, _session.Items);
+                await _eventContainer.ClientUnsubscribedTopicEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
             }
-            else if (reasonCode == MqttSubscribeReasonCode.GrantedQoS1)
+        }
+
+        return result;
+    }
+
+    CreateSubscriptionResult CreateSubscription(MqttTopicFilter topicFilter, uint subscriptionIdentifier, MqttSubscribeReasonCode reasonCode)
+    {
+        MqttQualityOfServiceLevel grantedQualityOfServiceLevel;
+
+        if (reasonCode == MqttSubscribeReasonCode.GrantedQoS0)
+        {
+            grantedQualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
+        }
+        else if (reasonCode == MqttSubscribeReasonCode.GrantedQoS1)
+        {
+            grantedQualityOfServiceLevel = MqttQualityOfServiceLevel.AtLeastOnce;
+        }
+        else if (reasonCode == MqttSubscribeReasonCode.GrantedQoS2)
+        {
+            grantedQualityOfServiceLevel = MqttQualityOfServiceLevel.ExactlyOnce;
+        }
+        else
+        {
+            throw new InvalidOperationException();
+        }
+
+        var subscription = new MqttSubscription(
+            topicFilter.Topic,
+            topicFilter.NoLocal,
+            topicFilter.RetainHandling,
+            topicFilter.RetainAsPublished,
+            grantedQualityOfServiceLevel,
+            subscriptionIdentifier);
+
+        bool isNewSubscription;
+
+        // Add to subscriptions and maintain topic hash dictionaries
+
+        _subscriptionsLock.EnterWriteLock();
+        try
+        {
+            MqttTopicHash.Calculate(topicFilter.Topic, out var topicHash, out _, out var hasWildcard);
+
+            if (_subscriptions.TryGetValue(topicFilter.Topic, out var existingSubscription))
             {
-                grantedQualityOfServiceLevel = MqttQualityOfServiceLevel.AtLeastOnce;
-            }
-            else if (reasonCode == MqttSubscribeReasonCode.GrantedQoS2)
-            {
-                grantedQualityOfServiceLevel = MqttQualityOfServiceLevel.ExactlyOnce;
-            }
-            else
-            {
-                throw new InvalidOperationException();
-            }
-
-            var subscription = new MqttSubscription(
-                topicFilter.Topic,
-                topicFilter.NoLocal,
-                topicFilter.RetainHandling,
-                topicFilter.RetainAsPublished,
-                grantedQualityOfServiceLevel,
-                subscriptionIdentifier);
-
-            bool isNewSubscription;
-
-            // Add to subscriptions and maintain topic hash dictionaries
-
-            _subscriptionsLock.EnterWriteLock();
-            try
-            {
-                MqttTopicHash.Calculate(topicFilter.Topic, out var topicHash, out _, out var hasWildcard);
-
-                if (_subscriptions.TryGetValue(topicFilter.Topic, out var existingSubscription))
-                {
-                    // must remove object from topic hash dictionary first
-                    if (hasWildcard)
-                    {
-                        if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
-                        {
-                            subscriptions.RemoveSubscription(existingSubscription);
-                            // no need to remove empty entry because we'll be adding subscription again below
-                        }
-                    }
-                    else
-                    {
-                        if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
-                        {
-                            subscriptions.Remove(existingSubscription);
-                            // no need to remove empty entry because we'll be adding subscription again below
-                        }
-                    }
-                }
-
-                isNewSubscription = existingSubscription == null;
-                _subscriptions[topicFilter.Topic] = subscription;
-
-                // Add or re-add to topic hash dictionary
+                // must remove object from topic hash dictionary first
                 if (hasWildcard)
                 {
-                    if (!_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
+                    if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                     {
-                        subscriptions = new TopicHashMaskSubscriptions();
-                        _wildcardSubscriptionsByTopicHash.Add(topicHash, subscriptions);
+                        subscriptions.RemoveSubscription(existingSubscription);
+                        // no need to remove empty entry because we'll be adding subscription again below
                     }
-
-                    subscriptions.AddSubscription(subscription);
                 }
                 else
                 {
-                    if (!_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
+                    if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                     {
-                        subscriptions = new HashSet<MqttSubscription>();
-                        _noWildcardSubscriptionsByTopicHash.Add(topicHash, subscriptions);
+                        subscriptions.Remove(existingSubscription);
+                        // no need to remove empty entry because we'll be adding subscription again below
                     }
-
-                    subscriptions.Add(subscription);
                 }
             }
-            finally
-            {
-                _subscriptionsLock.ExitWriteLock();
-            }
 
-            return new CreateSubscriptionResult
-            {
-                IsNewSubscription = isNewSubscription,
-                Subscription = subscription
-            };
-        }
+            isNewSubscription = existingSubscription == null;
+            _subscriptions[topicFilter.Topic] = subscription;
 
-        static void FilterRetainedApplicationMessages(
-            IList<MqttApplicationMessage> retainedMessages,
-            CreateSubscriptionResult createSubscriptionResult,
-            SubscribeResult subscribeResult)
-        {
-            if (createSubscriptionResult.Subscription.RetainHandling == MqttRetainHandling.DoNotSendOnSubscribe)
+            // Add or re-add to topic hash dictionary
+            if (hasWildcard)
             {
-                // This is a MQTT V5+ feature.
-                return;
-            }
-
-            if (createSubscriptionResult.Subscription.RetainHandling == MqttRetainHandling.SendAtSubscribeIfNewSubscriptionOnly && !createSubscriptionResult.IsNewSubscription)
-            {
-                // This is a MQTT V5+ feature.
-                return;
-            }
-
-            for (var index = retainedMessages.Count - 1; index >= 0; index--)
-            {
-                var retainedMessage = retainedMessages[index];
-                if (retainedMessage == null)
+                if (!_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                 {
-                    continue;
+                    subscriptions = new TopicHashMaskSubscriptions();
+                    _wildcardSubscriptionsByTopicHash.Add(topicHash, subscriptions);
                 }
 
-                if (MqttTopicFilterComparer.Compare(retainedMessage.Topic, createSubscriptionResult.Subscription.Topic) != MqttTopicFilterCompareResult.IsMatch)
-                {
-                    continue;
-                }
-
-                var retainedMessageMatch = new MqttRetainedMessageMatch(retainedMessage, createSubscriptionResult.Subscription.GrantedQualityOfServiceLevel);
-                if (retainedMessageMatch.SubscriptionQualityOfServiceLevel > retainedMessageMatch.ApplicationMessage.QualityOfServiceLevel)
-                {
-                    // UPGRADING the QoS is not allowed!
-                    // From MQTT spec: Subscribing to a Topic Filter at QoS 2 is equivalent to saying
-                    // "I would like to receive Messages matching this filter at the QoS with which they were published".
-                    // This means a publisher is responsible for determining the maximum QoS a Message can be delivered at,
-                    // but a subscriber is able to require that the Server downgrades the QoS to one more suitable for its usage.
-                    retainedMessageMatch.SubscriptionQualityOfServiceLevel = retainedMessageMatch.ApplicationMessage.QualityOfServiceLevel;
-                }
-
-                if (subscribeResult.RetainedMessages == null)
-                {
-                    subscribeResult.RetainedMessages = new List<MqttRetainedMessageMatch>();
-                }
-
-                subscribeResult.RetainedMessages.Add(retainedMessageMatch);
-
-                // Clear the retained message from the list because the client should receive every message only
-                // one time even if multiple subscriptions affect them.
-                retainedMessages[index] = null;
-            }
-        }
-
-        async Task<InterceptingSubscriptionEventArgs> InterceptSubscribe(
-            MqttTopicFilter topicFilter,
-            List<MqttUserProperty> userProperties,
-            CancellationToken cancellationToken)
-        {
-            var eventArgs = new InterceptingSubscriptionEventArgs(cancellationToken, _session.Id, _session.UserName, new MqttSessionStatus(_session), topicFilter, userProperties);
-
-            if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
-            {
-                eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS0;
-            }
-            else if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
-            {
-                eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS1;
-            }
-            else if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
-            {
-                eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS2;
-            }
-
-            if (topicFilter.Topic.StartsWith("$share/"))
-            {
-                eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.SharedSubscriptionsNotSupported;
+                subscriptions.AddSubscription(subscription);
             }
             else
             {
-                await _eventContainer.InterceptingSubscriptionEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
+                if (!_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
+                {
+                    subscriptions = new HashSet<MqttSubscription>();
+                    _noWildcardSubscriptionsByTopicHash.Add(topicHash, subscriptions);
+                }
+
+                subscriptions.Add(subscription);
+            }
+        }
+        finally
+        {
+            _subscriptionsLock.ExitWriteLock();
+        }
+
+        return new CreateSubscriptionResult
+        {
+            IsNewSubscription = isNewSubscription,
+            Subscription = subscription
+        };
+    }
+
+    static void FilterRetainedApplicationMessages(
+        IList<MqttApplicationMessage> retainedMessages,
+        CreateSubscriptionResult createSubscriptionResult,
+        SubscribeResult subscribeResult)
+    {
+        if (createSubscriptionResult.Subscription.RetainHandling == MqttRetainHandling.DoNotSendOnSubscribe)
+        {
+            // This is a MQTT V5+ feature.
+            return;
+        }
+
+        if (createSubscriptionResult.Subscription.RetainHandling == MqttRetainHandling.SendAtSubscribeIfNewSubscriptionOnly && !createSubscriptionResult.IsNewSubscription)
+        {
+            // This is a MQTT V5+ feature.
+            return;
+        }
+
+        for (var index = retainedMessages.Count - 1; index >= 0; index--)
+        {
+            var retainedMessage = retainedMessages[index];
+            if (retainedMessage == null)
+            {
+                continue;
             }
 
-            return eventArgs;
-        }
-
-        async Task<InterceptingUnsubscriptionEventArgs> InterceptUnsubscribe(
-            string topicFilter,
-            MqttSubscription mqttSubscription,
-            List<MqttUserProperty> userProperties,
-            CancellationToken cancellationToken)
-        {
-            var clientUnsubscribingTopicEventArgs = new InterceptingUnsubscriptionEventArgs(cancellationToken, _session.Id, _session.UserName, _session.Items, topicFilter, userProperties)
+            if (MqttTopicFilterComparer.Compare(retainedMessage.Topic, createSubscriptionResult.Subscription.Topic) != MqttTopicFilterCompareResult.IsMatch)
             {
-                Response =
-                {
-                    ReasonCode = mqttSubscription == null ? MqttUnsubscribeReasonCode.NoSubscriptionExisted : MqttUnsubscribeReasonCode.Success
-                }
-            };
+                continue;
+            }
 
-            await _eventContainer.InterceptingUnsubscriptionEvent.InvokeAsync(clientUnsubscribingTopicEventArgs).ConfigureAwait(false);
+            var retainedMessageMatch = new MqttRetainedMessageMatch(retainedMessage, createSubscriptionResult.Subscription.GrantedQualityOfServiceLevel);
+            if (retainedMessageMatch.SubscriptionQualityOfServiceLevel > retainedMessageMatch.ApplicationMessage.QualityOfServiceLevel)
+            {
+                // UPGRADING the QoS is not allowed!
+                // From MQTT spec: Subscribing to a Topic Filter at QoS 2 is equivalent to saying
+                // "I would like to receive Messages matching this filter at the QoS with which they were published".
+                // This means a publisher is responsible for determining the maximum QoS a Message can be delivered at,
+                // but a subscriber is able to require that the Server downgrades the QoS to one more suitable for its usage.
+                retainedMessageMatch.SubscriptionQualityOfServiceLevel = retainedMessageMatch.ApplicationMessage.QualityOfServiceLevel;
+            }
 
-            return clientUnsubscribingTopicEventArgs;
-        }
+            if (subscribeResult.RetainedMessages == null)
+            {
+                subscribeResult.RetainedMessages = new List<MqttRetainedMessageMatch>();
+            }
 
-        sealed class CreateSubscriptionResult
-        {
-            public bool IsNewSubscription { get; set; }
+            subscribeResult.RetainedMessages.Add(retainedMessageMatch);
 
-            public MqttSubscription Subscription { get; set; }
+            // Clear the retained message from the list because the client should receive every message only
+            // one time even if multiple subscriptions affect them.
+            retainedMessages[index] = null;
         }
     }
-}
+
+    async Task<InterceptingSubscriptionEventArgs> InterceptSubscribe(
+        MqttTopicFilter topicFilter,
+        List<MqttUserProperty> userProperties,
+        CancellationToken cancellationToken)
+    {
+        var eventArgs = new InterceptingSubscriptionEventArgs(cancellationToken, _session.Id, _session.UserName, new MqttSessionStatus(_session), topicFilter, userProperties);
+
+        if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
+        {
+            eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS0;
+        }
+        else if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
+        {
+            eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS1;
+        }
+        else if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
+        {
+            eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS2;
+        }
+
+        if (topicFilter.Topic.StartsWith("$share/"))
+        {
+            eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.SharedSubscriptionsNotSupported;
+        }
+        else
+        {
+            await _eventContainer.InterceptingSubscriptionEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
+        }
+
+        return eventArgs;
+    }
+
+    async Task<InterceptingUnsubscriptionEventArgs> InterceptUnsubscribe(
+        string topicFilter,
+        MqttSubscription mqttSubscription,
+        List<MqttUserProperty> userProperties,
+        CancellationToken cancellationToken)
+    {
+        var clientUnsubscribingTopicEventArgs = new InterceptingUnsubscriptionEventArgs(cancellationToken, _session.Id, _session.UserName, _session.Items, topicFilter, userProperties)
+        {
+            Response =
+            {
+                ReasonCode = mqttSubscription == null ? MqttUnsubscribeReasonCode.NoSubscriptionExisted : MqttUnsubscribeReasonCode.Success
+            }
+        };
+
+        await _eventContainer.InterceptingUnsubscriptionEvent.InvokeAsync(clientUnsubscribingTopicEventArgs).ConfigureAwait(false);
+
+        return clientUnsubscribingTopicEventArgs;
+    }
+
+    sealed class CreateSubscriptionResult
+    {
+        public bool IsNewSubscription { get; set; }
+
+        public MqttSubscription Subscription { get; set; }
+    }
+}

Source/MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs

@@ -2,148 +2,146 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Collections.ObjectModel;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Internal;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttRetainedMessagesManager
 {
-    public sealed class MqttRetainedMessagesManager
+    readonly Dictionary<string, MqttApplicationMessage> _messages = new Dictionary<string, MqttApplicationMessage>(4096);
+    readonly AsyncLock _storageAccessLock = new AsyncLock();
+
+    readonly MqttServerEventContainer _eventContainer;
+    readonly MqttNetSourceLogger _logger;
+
+    public MqttRetainedMessagesManager(MqttServerEventContainer eventContainer, IMqttNetLogger logger)
     {
-        readonly Dictionary<string, MqttApplicationMessage> _messages = new Dictionary<string, MqttApplicationMessage>(4096);
-        readonly AsyncLock _storageAccessLock = new AsyncLock();
+        _eventContainer = eventContainer ?? throw new ArgumentNullException(nameof(eventContainer));
 
-        readonly MqttServerEventContainer _eventContainer;
-        readonly MqttNetSourceLogger _logger;
+        ArgumentNullException.ThrowIfNull(logger);
 
-        public MqttRetainedMessagesManager(MqttServerEventContainer eventContainer, IMqttNetLogger logger)
+        _logger = logger.WithSource(nameof(MqttRetainedMessagesManager));
+    }
+
+    public async Task Start()
+    {
+        try
         {
-            _eventContainer = eventContainer ?? throw new ArgumentNullException(nameof(eventContainer));
+            var eventArgs = new LoadingRetainedMessagesEventArgs();
+            await _eventContainer.LoadingRetainedMessagesEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
 
-            ArgumentNullException.ThrowIfNull(logger);
-
-            _logger = logger.WithSource(nameof(MqttRetainedMessagesManager));
-        }
-
-        public async Task Start()
-        {
-            try
+            lock (_messages)
             {
-                var eventArgs = new LoadingRetainedMessagesEventArgs();
-                await _eventContainer.LoadingRetainedMessagesEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
+                _messages.Clear();
 
-                lock (_messages)
+                if (eventArgs.LoadedRetainedMessages != null)
                 {
-                    _messages.Clear();
-
-                    if (eventArgs.LoadedRetainedMessages != null)
+                    foreach (var retainedMessage in eventArgs.LoadedRetainedMessages)
                     {
-                        foreach (var retainedMessage in eventArgs.LoadedRetainedMessages)
-                        {
-                            _messages[retainedMessage.Topic] = retainedMessage;
-                        }
+                        _messages[retainedMessage.Topic] = retainedMessage;
                     }
                 }
             }
-            catch (Exception exception)
-            {
-                _logger.Error(exception, "Unhandled exception while loading retained messages.");
-            }
         }
-
-        public async Task UpdateMessage(string clientId, MqttApplicationMessage applicationMessage)
+        catch (Exception exception)
         {
-            ArgumentNullException.ThrowIfNull(applicationMessage);
+            _logger.Error(exception, "Unhandled exception while loading retained messages.");
+        }
+    }
 
-            try
+    public async Task UpdateMessage(string clientId, MqttApplicationMessage applicationMessage)
+    {
+        ArgumentNullException.ThrowIfNull(applicationMessage);
+
+        try
+        {
+            List<MqttApplicationMessage> messagesForSave = null;
+            var saveIsRequired = false;
+
+            lock (_messages)
             {
-                List<MqttApplicationMessage> messagesForSave = null;
-                var saveIsRequired = false;
+                var payload = applicationMessage.Payload;
+                var hasPayload = payload.Length > 0;
 
-                lock (_messages)
+                if (!hasPayload)
                 {
-                    var payload = applicationMessage.Payload;
-                    var hasPayload = payload.Length > 0;
-
-                    if (!hasPayload)
+                    saveIsRequired = _messages.Remove(applicationMessage.Topic);
+                    _logger.Verbose("Client '{0}' cleared retained message for topic '{1}'.", clientId, applicationMessage.Topic);
+                }
+                else
+                {
+                    if (!_messages.TryGetValue(applicationMessage.Topic, out var existingMessage))
                     {
-                        saveIsRequired = _messages.Remove(applicationMessage.Topic);
-                        _logger.Verbose("Client '{0}' cleared retained message for topic '{1}'.", clientId, applicationMessage.Topic);
+                        _messages[applicationMessage.Topic] = applicationMessage;
+                        saveIsRequired = true;
                     }
                     else
                     {
-                        if (!_messages.TryGetValue(applicationMessage.Topic, out var existingMessage))
+                        if (existingMessage.QualityOfServiceLevel != applicationMessage.QualityOfServiceLevel ||
+                            !MqttMemoryHelper.SequenceEqual(existingMessage.Payload, payload))
                         {
                             _messages[applicationMessage.Topic] = applicationMessage;
                             saveIsRequired = true;
                         }
-                        else
-                        {
-                            if (existingMessage.QualityOfServiceLevel != applicationMessage.QualityOfServiceLevel ||
-                                !MqttMemoryHelper.SequenceEqual(existingMessage.Payload, payload))
-                            {
-                                _messages[applicationMessage.Topic] = applicationMessage;
-                                saveIsRequired = true;
-                            }
-                        }
-
-                        _logger.Verbose("Client '{0}' set retained message for topic '{1}'.", clientId, applicationMessage.Topic);
                     }
 
-                    if (saveIsRequired)
-                    {
-                        messagesForSave = new List<MqttApplicationMessage>(_messages.Values);
-                    }
+                    _logger.Verbose("Client '{0}' set retained message for topic '{1}'.", clientId, applicationMessage.Topic);
                 }
 
                 if (saveIsRequired)
                 {
-                    using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
-                    {
-                        var eventArgs = new RetainedMessageChangedEventArgs(clientId, applicationMessage, messagesForSave);
-                        await _eventContainer.RetainedMessageChangedEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
-                    }
+                    messagesForSave = new List<MqttApplicationMessage>(_messages.Values);
                 }
             }
-            catch (Exception exception)
-            {
-                _logger.Error(exception, "Unhandled exception while handling retained messages.");
-            }
-        }
 
-        public Task<IList<MqttApplicationMessage>> GetMessages()
-        {
-            lock (_messages)
+            if (saveIsRequired)
             {
-                var result = new List<MqttApplicationMessage>(_messages.Values);
-                return Task.FromResult((IList<MqttApplicationMessage>)result);
-            }
-        }
-
-        public Task<MqttApplicationMessage> GetMessage(string topic)
-        {
-            lock (_messages)
-            {
-                if (_messages.TryGetValue(topic, out var message))
+                using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
                 {
-                    return Task.FromResult(message);
+                    var eventArgs = new RetainedMessageChangedEventArgs(clientId, applicationMessage, messagesForSave);
+                    await _eventContainer.RetainedMessageChangedEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
                 }
             }
+        }
+        catch (Exception exception)
+        {
+            _logger.Error(exception, "Unhandled exception while handling retained messages.");
+        }
+    }
 
-            return Task.FromResult<MqttApplicationMessage>(null);
+    public Task<IList<MqttApplicationMessage>> GetMessages()
+    {
+        lock (_messages)
+        {
+            var result = new List<MqttApplicationMessage>(_messages.Values);
+            return Task.FromResult((IList<MqttApplicationMessage>)result);
+        }
+    }
+
+    public Task<MqttApplicationMessage> GetMessage(string topic)
+    {
+        lock (_messages)
+        {
+            if (_messages.TryGetValue(topic, out var message))
+            {
+                return Task.FromResult(message);
+            }
         }
 
-        public async Task ClearMessages()
-        {
-            lock (_messages)
-            {
-                _messages.Clear();
-            }
+        return Task.FromResult<MqttApplicationMessage>(null);
+    }
 
-            using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
-            {
-                await _eventContainer.RetainedMessagesClearedEvent.InvokeAsync(EventArgs.Empty).ConfigureAwait(false);
-            }
+    public async Task ClearMessages()
+    {
+        lock (_messages)
+        {
+            _messages.Clear();
+        }
+
+        using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
+        {
+            await _eventContainer.RetainedMessagesClearedEvent.InvokeAsync(EventArgs.Empty).ConfigureAwait(false);
         }
     }
 }

Source/MQTTnet.Server/Internal/MqttServerEventContainer.cs

@@ -4,52 +4,51 @@
 
 using MQTTnet.Internal;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttServerEventContainer
 {
-    public sealed class MqttServerEventContainer
-    {
-        public AsyncEvent<ApplicationMessageNotConsumedEventArgs> ApplicationMessageNotConsumedEvent { get; } = new AsyncEvent<ApplicationMessageNotConsumedEventArgs>();
+    public AsyncEvent<ApplicationMessageNotConsumedEventArgs> ApplicationMessageNotConsumedEvent { get; } = new AsyncEvent<ApplicationMessageNotConsumedEventArgs>();
 
-        public AsyncEvent<ClientAcknowledgedPublishPacketEventArgs> ClientAcknowledgedPublishPacketEvent { get; } = new AsyncEvent<ClientAcknowledgedPublishPacketEventArgs>();
+    public AsyncEvent<ClientAcknowledgedPublishPacketEventArgs> ClientAcknowledgedPublishPacketEvent { get; } = new AsyncEvent<ClientAcknowledgedPublishPacketEventArgs>();
 
-        public AsyncEvent<ClientConnectedEventArgs> ClientConnectedEvent { get; } = new AsyncEvent<ClientConnectedEventArgs>();
+    public AsyncEvent<ClientConnectedEventArgs> ClientConnectedEvent { get; } = new AsyncEvent<ClientConnectedEventArgs>();
 
-        public AsyncEvent<ClientDisconnectedEventArgs> ClientDisconnectedEvent { get; } = new AsyncEvent<ClientDisconnectedEventArgs>();
+    public AsyncEvent<ClientDisconnectedEventArgs> ClientDisconnectedEvent { get; } = new AsyncEvent<ClientDisconnectedEventArgs>();
 
-        public AsyncEvent<ClientSubscribedTopicEventArgs> ClientSubscribedTopicEvent { get; } = new AsyncEvent<ClientSubscribedTopicEventArgs>();
+    public AsyncEvent<ClientSubscribedTopicEventArgs> ClientSubscribedTopicEvent { get; } = new AsyncEvent<ClientSubscribedTopicEventArgs>();
 
-        public AsyncEvent<ClientUnsubscribedTopicEventArgs> ClientUnsubscribedTopicEvent { get; } = new AsyncEvent<ClientUnsubscribedTopicEventArgs>();
+    public AsyncEvent<ClientUnsubscribedTopicEventArgs> ClientUnsubscribedTopicEvent { get; } = new AsyncEvent<ClientUnsubscribedTopicEventArgs>();
 
-        public AsyncEvent<InterceptingClientApplicationMessageEnqueueEventArgs> InterceptingClientEnqueueEvent { get; } = new AsyncEvent<InterceptingClientApplicationMessageEnqueueEventArgs>();
-        
-        public AsyncEvent<ApplicationMessageEnqueuedEventArgs> ApplicationMessageEnqueuedOrDroppedEvent { get; } = new AsyncEvent<ApplicationMessageEnqueuedEventArgs>();
+    public AsyncEvent<InterceptingClientApplicationMessageEnqueueEventArgs> InterceptingClientEnqueueEvent { get; } = new AsyncEvent<InterceptingClientApplicationMessageEnqueueEventArgs>();
 
-        public AsyncEvent<QueueMessageOverwrittenEventArgs> QueuedApplicationMessageOverwrittenEvent { get; } = new AsyncEvent<QueueMessageOverwrittenEventArgs>();
+    public AsyncEvent<ApplicationMessageEnqueuedEventArgs> ApplicationMessageEnqueuedOrDroppedEvent { get; } = new AsyncEvent<ApplicationMessageEnqueuedEventArgs>();
 
-        public AsyncEvent<InterceptingPacketEventArgs> InterceptingInboundPacketEvent { get; } = new AsyncEvent<InterceptingPacketEventArgs>();
+    public AsyncEvent<QueueMessageOverwrittenEventArgs> QueuedApplicationMessageOverwrittenEvent { get; } = new AsyncEvent<QueueMessageOverwrittenEventArgs>();
 
-        public AsyncEvent<InterceptingPacketEventArgs> InterceptingOutboundPacketEvent { get; } = new AsyncEvent<InterceptingPacketEventArgs>();
+    public AsyncEvent<InterceptingPacketEventArgs> InterceptingInboundPacketEvent { get; } = new AsyncEvent<InterceptingPacketEventArgs>();
 
-        public AsyncEvent<InterceptingPublishEventArgs> InterceptingPublishEvent { get; } = new AsyncEvent<InterceptingPublishEventArgs>();
+    public AsyncEvent<InterceptingPacketEventArgs> InterceptingOutboundPacketEvent { get; } = new AsyncEvent<InterceptingPacketEventArgs>();
 
-        public AsyncEvent<InterceptingSubscriptionEventArgs> InterceptingSubscriptionEvent { get; } = new AsyncEvent<InterceptingSubscriptionEventArgs>();
+    public AsyncEvent<InterceptingPublishEventArgs> InterceptingPublishEvent { get; } = new AsyncEvent<InterceptingPublishEventArgs>();
 
-        public AsyncEvent<InterceptingUnsubscriptionEventArgs> InterceptingUnsubscriptionEvent { get; } = new AsyncEvent<InterceptingUnsubscriptionEventArgs>();
+    public AsyncEvent<InterceptingSubscriptionEventArgs> InterceptingSubscriptionEvent { get; } = new AsyncEvent<InterceptingSubscriptionEventArgs>();
 
-        public AsyncEvent<LoadingRetainedMessagesEventArgs> LoadingRetainedMessagesEvent { get; } = new AsyncEvent<LoadingRetainedMessagesEventArgs>();
+    public AsyncEvent<InterceptingUnsubscriptionEventArgs> InterceptingUnsubscriptionEvent { get; } = new AsyncEvent<InterceptingUnsubscriptionEventArgs>();
 
-        public AsyncEvent<EventArgs> PreparingSessionEvent { get; } = new AsyncEvent<EventArgs>();
+    public AsyncEvent<LoadingRetainedMessagesEventArgs> LoadingRetainedMessagesEvent { get; } = new AsyncEvent<LoadingRetainedMessagesEventArgs>();
 
-        public AsyncEvent<RetainedMessageChangedEventArgs> RetainedMessageChangedEvent { get; } = new AsyncEvent<RetainedMessageChangedEventArgs>();
+    public AsyncEvent<EventArgs> PreparingSessionEvent { get; } = new AsyncEvent<EventArgs>();
 
-        public AsyncEvent<EventArgs> RetainedMessagesClearedEvent { get; } = new AsyncEvent<EventArgs>();
+    public AsyncEvent<RetainedMessageChangedEventArgs> RetainedMessageChangedEvent { get; } = new AsyncEvent<RetainedMessageChangedEventArgs>();
 
-        public AsyncEvent<SessionDeletedEventArgs> SessionDeletedEvent { get; } = new AsyncEvent<SessionDeletedEventArgs>();
+    public AsyncEvent<EventArgs> RetainedMessagesClearedEvent { get; } = new AsyncEvent<EventArgs>();
 
-        public AsyncEvent<EventArgs> StartedEvent { get; } = new AsyncEvent<EventArgs>();
+    public AsyncEvent<SessionDeletedEventArgs> SessionDeletedEvent { get; } = new AsyncEvent<SessionDeletedEventArgs>();
 
-        public AsyncEvent<EventArgs> StoppedEvent { get; } = new AsyncEvent<EventArgs>();
+    public AsyncEvent<EventArgs> StartedEvent { get; } = new AsyncEvent<EventArgs>();
 
-        public AsyncEvent<ValidatingConnectionEventArgs> ValidatingConnectionEvent { get; } = new AsyncEvent<ValidatingConnectionEventArgs>();
-    }
+    public AsyncEvent<EventArgs> StoppedEvent { get; } = new AsyncEvent<EventArgs>();
+
+    public AsyncEvent<ValidatingConnectionEventArgs> ValidatingConnectionEvent { get; } = new AsyncEvent<ValidatingConnectionEventArgs>();
 }

Source/MQTTnet.Server/Internal/MqttServerKeepAliveMonitor.cs

@@ -6,130 +6,129 @@ using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Internal;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttServerKeepAliveMonitor
 {
-    public sealed class MqttServerKeepAliveMonitor
+    static readonly MqttServerClientDisconnectOptions DefaultDisconnectOptions = new MqttServerClientDisconnectOptions
     {
-        static readonly MqttServerClientDisconnectOptions DefaultDisconnectOptions = new MqttServerClientDisconnectOptions
+        ReasonCode = MqttDisconnectReasonCode.KeepAliveTimeout,
+        UserProperties = null,
+        ReasonString = null,
+        ServerReference = null
+    };
+
+    readonly MqttNetSourceLogger _logger;
+    readonly MqttServerOptions _options;
+    readonly MqttClientSessionsManager _sessionsManager;
+
+    public MqttServerKeepAliveMonitor(MqttServerOptions options, MqttClientSessionsManager sessionsManager, IMqttNetLogger logger)
+    {
+        _options = options ?? throw new ArgumentNullException(nameof(options));
+        _sessionsManager = sessionsManager ?? throw new ArgumentNullException(nameof(sessionsManager));
+
+        ArgumentNullException.ThrowIfNull(logger);
+
+        _logger = logger.WithSource(nameof(MqttServerKeepAliveMonitor));
+    }
+
+    public void Start(CancellationToken cancellationToken)
+    {
+        // The keep alive monitor spawns a real new thread (LongRunning) because it does not
+        // support async/await. Async etc. is avoided here because the thread will usually check
+        // the connections every few milliseconds and thus the context changes (due to async) are
+        // only consuming resources. Also there is just 1 thread for the entire server which is fine at all!
+        Task.Factory.StartNew(_ => DoWork(cancellationToken), cancellationToken, TaskCreationOptions.LongRunning).RunInBackground(_logger);
+    }
+
+    void DoWork(CancellationToken cancellationToken)
+    {
+        try
         {
-            ReasonCode = MqttDisconnectReasonCode.KeepAliveTimeout,
-            UserProperties = null,
-            ReasonString = null,
-            ServerReference = null
-        };
+            _logger.Info("Starting keep alive monitor");
 
-        readonly MqttNetSourceLogger _logger;
-        readonly MqttServerOptions _options;
-        readonly MqttClientSessionsManager _sessionsManager;
-
-        public MqttServerKeepAliveMonitor(MqttServerOptions options, MqttClientSessionsManager sessionsManager, IMqttNetLogger logger)
-        {
-            _options = options ?? throw new ArgumentNullException(nameof(options));
-            _sessionsManager = sessionsManager ?? throw new ArgumentNullException(nameof(sessionsManager));
-
-            ArgumentNullException.ThrowIfNull(logger);
-
-            _logger = logger.WithSource(nameof(MqttServerKeepAliveMonitor));
-        }
-
-        public void Start(CancellationToken cancellationToken)
-        {
-            // The keep alive monitor spawns a real new thread (LongRunning) because it does not
-            // support async/await. Async etc. is avoided here because the thread will usually check
-            // the connections every few milliseconds and thus the context changes (due to async) are
-            // only consuming resources. Also there is just 1 thread for the entire server which is fine at all!
-            Task.Factory.StartNew(_ => DoWork(cancellationToken), cancellationToken, TaskCreationOptions.LongRunning).RunInBackground(_logger);
-        }
-
-        void DoWork(CancellationToken cancellationToken)
-        {
-            try
+            while (!cancellationToken.IsCancellationRequested)
             {
-                _logger.Info("Starting keep alive monitor");
-
-                while (!cancellationToken.IsCancellationRequested)
-                {
-                    TryProcessClients();
-                    Sleep(_options.KeepAliveOptions.MonitorInterval);
-                }
-            }
-            catch (OperationCanceledException)
-            {
-            }
-            catch (Exception exception)
-            {
-                _logger.Error(exception, "Unhandled exception while checking keep alive timeouts");
-            }
-            finally
-            {
-                _logger.Verbose("Stopped checking keep alive timeout");
+                TryProcessClients();
+                Sleep(_options.KeepAliveOptions.MonitorInterval);
             }
         }
-
-        static void Sleep(TimeSpan timeout)
+        catch (OperationCanceledException)
         {
-            try
-            {
-                Thread.Sleep(timeout);
-            }
-            catch (ThreadAbortException)
-            {
-                // The ThreadAbortException is not actively catched in this project.
-                // So we use a one which is similar and will be catched properly.
-                throw new OperationCanceledException();
-            }
         }
-
-        void TryProcessClient(MqttConnectedClient connection, DateTime now)
+        catch (Exception exception)
         {
-            try
-            {
-                if (!connection.IsRunning)
-                {
-                    // The connection is already dead or just created so there is no need to check it.
-                    return;
-                }
-
-                if (connection.ConnectPacket.KeepAlivePeriod == 0)
-                {
-                    // The keep alive feature is not used by the current connection.
-                    return;
-                }
-
-                // Values described here: [MQTT-3.1.2-24].
-                // If the client sends 5 sec. the server will allow up to 7.5 seconds.
-                // If the client sends 1 sec. the server will allow up to 1.5 seconds.
-                var maxSecondsWithoutPacket = connection.ConnectPacket.KeepAlivePeriod * 1.5D;
-
-                var secondsWithoutPackage = (now - connection.Statistics.LastPacketSentTimestamp).TotalSeconds;
-                if (secondsWithoutPackage < maxSecondsWithoutPacket)
-                {
-                    // A packet was received before the timeout is affected.
-                    return;
-                }
-
-                _logger.Warning("Client '{0}': Did not receive any packet or keep alive signal", connection.Id);
-
-                // Execute the disconnection in background so that the keep alive monitor can continue
-                // with checking other connections.
-                // We do not need to wait for the task so no await is needed.
-                // Also the internal state of the connection must be swapped to "Finalizing" because the
-                // next iteration of the keep alive timer happens.
-                _ = connection.StopAsync(DefaultDisconnectOptions);
-            }
-            catch (Exception exception)
-            {
-                _logger.Error(exception, "Client {0}: Unhandled exception while checking keep alive timeouts", connection.Id);
-            }
+            _logger.Error(exception, "Unhandled exception while checking keep alive timeouts");
         }
-
-        void TryProcessClients()
+        finally
         {
-            var now = DateTime.UtcNow;
-            foreach (var client in _sessionsManager.GetClients())
+            _logger.Verbose("Stopped checking keep alive timeout");
+        }
+    }
+
+    static void Sleep(TimeSpan timeout)
+    {
+        try
+        {
+            Thread.Sleep(timeout);
+        }
+        catch (ThreadAbortException)
+        {
+            // The ThreadAbortException is not actively catched in this project.
+            // So we use a one which is similar and will be catched properly.
+            throw new OperationCanceledException();
+        }
+    }
+
+    void TryProcessClient(MqttConnectedClient connection, DateTime now)
+    {
+        try
+        {
+            if (!connection.IsRunning)
             {
-                TryProcessClient(client, now);
+                // The connection is already dead or just created so there is no need to check it.
+                return;
             }
+
+            if (connection.ConnectPacket.KeepAlivePeriod == 0)
+            {
+                // The keep alive feature is not used by the current connection.
+                return;
+            }
+
+            // Values described here: [MQTT-3.1.2-24].
+            // If the client sends 5 sec. the server will allow up to 7.5 seconds.
+            // If the client sends 1 sec. the server will allow up to 1.5 seconds.
+            var maxSecondsWithoutPacket = connection.ConnectPacket.KeepAlivePeriod * 1.5D;
+
+            var secondsWithoutPackage = (now - connection.Statistics.LastPacketSentTimestamp).TotalSeconds;
+            if (secondsWithoutPackage < maxSecondsWithoutPacket)
+            {
+                // A packet was received before the timeout is affected.
+                return;
+            }
+
+            _logger.Warning("Client '{0}': Did not receive any packet or keep alive signal", connection.Id);
+
+            // Execute the disconnection in background so that the keep alive monitor can continue
+            // with checking other connections.
+            // We do not need to wait for the task so no await is needed.
+            // Also the internal state of the connection must be swapped to "Finalizing" because the
+            // next iteration of the keep alive timer happens.
+            _ = connection.StopAsync(DefaultDisconnectOptions);
+        }
+        catch (Exception exception)
+        {
+            _logger.Error(exception, "Client {0}: Unhandled exception while checking keep alive timeouts", connection.Id);
+        }
+    }
+
+    void TryProcessClients()
+    {
+        var now = DateTime.UtcNow;
+        foreach (var client in _sessionsManager.GetClients())
+        {
+            TryProcessClient(client, now);
         }
     }
 }

Source/MQTTnet.Server/Internal/MqttSessionsStorage.cs

@@ -4,78 +4,77 @@
 
 using System.Collections.ObjectModel;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttSessionsStorage
 {
-    public sealed class MqttSessionsStorage
+    readonly Dictionary<string, MqttSession> _sessions = new Dictionary<string, MqttSession>(4096);
+
+    public void Clear()
     {
-        readonly Dictionary<string, MqttSession> _sessions = new Dictionary<string, MqttSession>(4096);
+        // Make sure that the sessions are also getting disposed!
+        // This object can be reused after disposing.
+        Dispose();
+    }
 
-        public void Clear()
+    public void Dispose()
+    {
+        foreach (var sessionItem in _sessions)
         {
-            // Make sure that the sessions are also getting disposed!
-            // This object can be reused after disposing.
-            Dispose();
+            sessionItem.Value.Dispose();
         }
 
-        public void Dispose()
+        _sessions.Clear();
+    }
+
+    public IReadOnlyCollection<MqttSession> ReadAllSessions()
+    {
+        return new ReadOnlyCollection<MqttSession>(_sessions.Values.ToList());
+    }
+
+    public bool TryGetSession(string id, out MqttSession session)
+    {
+        ArgumentNullException.ThrowIfNull(id);
+
+        if (!_sessions.TryGetValue(id, out session))
         {
-            foreach (var sessionItem in _sessions)
-            {
-                sessionItem.Value.Dispose();
-            }
-
-            _sessions.Clear();
-        }
-
-        public IReadOnlyCollection<MqttSession> ReadAllSessions()
-        {
-            return new ReadOnlyCollection<MqttSession>(_sessions.Values.ToList());
-        }
-
-        public bool TryGetSession(string id, out MqttSession session)
-        {
-            ArgumentNullException.ThrowIfNull(id);
-
-            if (!_sessions.TryGetValue(id, out session))
-            {
-                return false;
-            }
-
-            // If the Session Expiry Interval is 0xFFFFFFFF (UINT_MAX), the Session does not expire.
-            if (session.ExpiryInterval > 0 && session.ExpiryInterval != uint.MaxValue)
-            {
-                if (session.DisconnectedTimestamp.HasValue)
-                {
-                    if (DateTime.UtcNow > session.DisconnectedTimestamp.Value.AddSeconds(session.ExpiryInterval))
-                    {
-                        TryRemoveSession(id, out var oldSession);
-                        oldSession?.Dispose();
-                        return false;
-                    }
-                }
-            }
-
-            return true;
-        }
-
-        public bool TryRemoveSession(string id, out MqttSession session)
-        {
-            ArgumentNullException.ThrowIfNull(id);
-
-            if (_sessions.TryGetValue(id, out session))
-            {
-                _sessions.Remove(id);
-                return true;
-            }
-
             return false;
         }
 
-        public void UpdateSession(string id, MqttSession session)
+        // If the Session Expiry Interval is 0xFFFFFFFF (UINT_MAX), the Session does not expire.
+        if (session.ExpiryInterval > 0 && session.ExpiryInterval != uint.MaxValue)
         {
-            ArgumentNullException.ThrowIfNull(id);
-
-            _sessions[id] = session;
+            if (session.DisconnectedTimestamp.HasValue)
+            {
+                if (DateTime.UtcNow > session.DisconnectedTimestamp.Value.AddSeconds(session.ExpiryInterval))
+                {
+                    TryRemoveSession(id, out var oldSession);
+                    oldSession?.Dispose();
+                    return false;
+                }
+            }
         }
+
+        return true;
+    }
+
+    public bool TryRemoveSession(string id, out MqttSession session)
+    {
+        ArgumentNullException.ThrowIfNull(id);
+
+        if (_sessions.TryGetValue(id, out session))
+        {
+            _sessions.Remove(id);
+            return true;
+        }
+
+        return false;
+    }
+
+    public void UpdateSession(string id, MqttSession session)
+    {
+        ArgumentNullException.ThrowIfNull(id);
+
+        _sessions[id] = session;
     }
 }

Source/MQTTnet.Server/Internal/MqttSubscription.cs

@@ -4,47 +4,46 @@
 
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class MqttSubscription
 {
-    public sealed class MqttSubscription
+    public MqttSubscription(
+        string topic,
+        bool noLocal,
+        MqttRetainHandling retainHandling,
+        bool retainAsPublished,
+        MqttQualityOfServiceLevel qualityOfServiceLevel,
+        uint identifier)
     {
-        public MqttSubscription(
-            string topic,
-            bool noLocal,
-            MqttRetainHandling retainHandling,
-            bool retainAsPublished,
-            MqttQualityOfServiceLevel qualityOfServiceLevel,
-            uint identifier)
-        {
-            Topic = topic;
-            NoLocal = noLocal;
-            RetainHandling = retainHandling;
-            RetainAsPublished = retainAsPublished;
-            GrantedQualityOfServiceLevel = qualityOfServiceLevel;
-            Identifier = identifier;
+        Topic = topic;
+        NoLocal = noLocal;
+        RetainHandling = retainHandling;
+        RetainAsPublished = retainAsPublished;
+        GrantedQualityOfServiceLevel = qualityOfServiceLevel;
+        Identifier = identifier;
 
-            MqttTopicHash.Calculate(Topic, out var hash, out var hashMask, out var hasWildcard);
-            TopicHash = hash;
-            TopicHashMask = hashMask;
-            TopicHasWildcard = hasWildcard;
-        }
-
-        public MqttQualityOfServiceLevel GrantedQualityOfServiceLevel { get; }
-
-        public uint Identifier { get; }
-
-        public bool NoLocal { get; }
-
-        public bool RetainAsPublished { get; }
-
-        public MqttRetainHandling RetainHandling { get; }
-
-        public string Topic { get; }
-
-        public ulong TopicHash { get; }
-
-        public ulong TopicHashMask { get; }
-
-        public bool TopicHasWildcard { get; }
+        MqttTopicHash.Calculate(Topic, out var hash, out var hashMask, out var hasWildcard);
+        TopicHash = hash;
+        TopicHashMask = hashMask;
+        TopicHasWildcard = hasWildcard;
     }
+
+    public MqttQualityOfServiceLevel GrantedQualityOfServiceLevel { get; }
+
+    public uint Identifier { get; }
+
+    public bool NoLocal { get; }
+
+    public bool RetainAsPublished { get; }
+
+    public MqttRetainHandling RetainHandling { get; }
+
+    public string Topic { get; }
+
+    public ulong TopicHash { get; }
+
+    public ulong TopicHashMask { get; }
+
+    public bool TopicHasWildcard { get; }
 }

Source/MQTTnet.Server/Internal/MqttTopicHash.cs

@@ -2,267 +2,266 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+/*
+ * The MqttSubscription object stores subscription parameters and calculates
+ * topic hashes.
+ *
+ * Use of Topic Hashes to improve message processing performance
+ * =============================================================
+ *
+ * Motivation
+ * -----------
+ * In a typical use case for MQTT there may be many publishers (sensors or
+ * other devices in the field) and few subscribers (monitoring all or many topics).
+ * Each publisher may have one or more topic(s) to publish and therefore both, the
+ * number of publishers and the number of topics may be large.
+ *
+ * Maintaining subscribers in a separate container
+ * -----------------------------------------------
+ * Instead of placing all sessions into a single _sessions container, subscribers
+ * are added into another _subscriberSessions container (if a client is a
+ * subscriber and a publisher then the client is present in both containers). The
+ * cost is some additional bookkeeping work upon subscription where each client
+ * session needs to maintain a list of subscribed topics.
+ *
+ * When the client subscribes to the first topic, then the session manager adds
+ * the client to the _subscriberSessions container, and when the client
+ * unsubscribes from the last topic then the session manager removes the client
+ * from the container. Now, when an application message arrives, only the list of
+ * subscribers need processing instead of looping through potentially thousands of
+ * publishers.
+ *
+ * Improving subscriber topic lookup
+ * ---------------------------------
+ * For each subscriber, it needs to be determined whether an application message
+ * matches any topic the subscriber has subscribed to. There may only be few
+ * subscribers but there may be many subscribed topics, including wildcard topics.
+ *
+ * The implemented approach uses a topic hash and a hash mask calculated on the
+ * subscribed topic and the published topic (the application message topic) to
+ * find candidates for a match, with the existing match logic evaluating a reduced
+ * number of candidates.
+ *
+ * For each subscription, the topic hash and a hash mask is stored with the
+ * subscription, and for each application message received, the hash is calculated
+ * for the published topic before attempting to find matching subscriptions. The
+ * hash calculation itself is simple and does not have a large performance impact.
+ *
+ * We'll first explain how topic hashes and hash masks are constructed and then how
+ * they are used.
+ *
+ * Topic hash
+ * ----------
+ * Topic hashes are stored as 64-bit numbers. Each byte within the 64-bit number
+ * relates to one MQTT topic level. A checksum is calculated for each topic level
+ * by iterating over the characters within the topic level (cast to byte) and the
+ * result is stored into the corresponding byte of the 64-bit number. If a topic
+ * level contains a wildcard character, then 0x00 is stored instead of the
+ * checksum.
+ *
+ * If there are less than 8 levels then the rest of the 64-bit number is filled
+ * with 0xff. If there are more than 8 levels then topics where the first 8 MQTT
+ * topic levels are identical will have the same hash value.
+ *
+ * This is the topic hash for the MQTT topic below: 0x655D4AF1FFFFFF
+ *
+ * client1/building1/level1/sensor1 (empty) (empty) (empty) (empty)
+ * \_____/ \_______/ \____/ \_____/ \_____/ \_____/ \_____/ \_____/
+ *    |        |       |       |       |       |       |       |
+ *   0x65     0x5D    0x4A   0xF1     0xFF    0xFF    0xFF    0xFF
+ *
+ * This is the topic hash for an MQTT topic containing a wildcard: 0x655D00F1FFFFFF
+ *
+ * client1/building1/ + /sensor1 (empty) (empty) (empty) (empty)
+ * \_____/ \_______/ \_/ \_____/ \_____/ \_____/ \_____/ \_____/
+ *    |        |      |     |       |       |       |       |
+ *   0x65     0x5D    0    0xF1    0xFF    0xFF    0xFF    0xFF
+ *
+ * For topics that contain the multi level wildcard # at the end, the topic hash
+ * is filled with 0x00: 0x65004A00000000
+ *
+ * client1/ + /level1/ #  (empty) (empty) (empty) (empty)
+ * \_____/ \_/ \____/ \_/ \_____/ \_____/ \_____/ \_____/
+ *    |     |    |     |     |       |       |       |
+ *   0x65   0   0x4A   0     0       0       0       0
+ *
+ *
+ * Topic hash mask
+ * ---------------
+ * The hash mask simply contains 0xFF for non-wildcard topic levels and 0x00 for
+ * wildcard topic levels. Here are the topic hash masks for the examples above.
+ *
+ * client1/building1/level1/sensor1 (empty) (empty) (empty) (empty)
+ * \_____/ \_______/ \____/ \_____/ \_____/ \_____/ \_____/ \_____/
+ *    |        |       |       |       |       |       |       |
+ *   0xFF     0xFF    0xFF   0xFF     0xFF    0xFF    0xFF    0xFF
+ *
+ * client1/building1/ + /sensor1 (empty) (empty) (empty) (empty)
+ * \_____/ \_______/ \_/ \_____/ \_____/ \_____/ \_____/ \_____/
+ *    |        |      |     |       |       |       |       |
+ *   0xFF     0xFF    0    0xFF    0xFF    0xFF    0xFF    0xFF
+ *
+ * client1/ + /level1/ #  (empty) (empty) (empty) (empty)
+ * \_____/ \_/ \____/ \_/ \_____/ \_____/ \_____/ \_____/
+ *    |     |    |     |     |       |       |       |
+ *   0xFF   0    0xFF  0     0       0       0       0
+ *
+ *
+ * Topic hash and hash mask properties
+ * -----------------------------------
+ * The following properties of topic hashes and hash masks can be exploited to
+ * find potentially matching subscribed topics for a given published topic.
+ *
+ * (1) If a subscribed topic does not contain wildcards then the topic hash of the
+ * subscribed topic must be equal to the topic hash of the published topic,
+ * otherwise the subscribed topic cannot be a candidate for a match.
+ *
+ * (2) If a subscribed topic contains wildcards then the hash of the published
+ * topic masked with the subscribed topic's hash mask must be equal to the hash of
+ * the subscribed topic. I.e. a subscribed topic is a candidate for a match if:
+ * (publishedTopicHash & subscribedTopicHashMask) == subscribedTopicHash
+ *
+ * (3) If a subscribed topic contains wildcards then any potentially matching
+ * published topic must have a hash value that is greater than or equal to the
+ * hash value of the subscribed topic (because the subscribed topic contains
+ * zeroes in wildcard positions).
+ *
+ * Match finding
+ * -------------
+ * The subscription manager maintains two separate dictionaries to assist finding
+ * matches using topic hashes: a _noWildcardSubscriptionsByTopicHash dictionary
+ * containing all subscriptions that do not have wildcards, and a
+ * _wildcardSubscriptionsByTopicHash dictionary containing subscriptions with
+ * wildcards.
+ *
+ * For subscriptions without wildcards, all potential candidates for a match are
+ * obtained by a single look-up (exploiting point 1 above).
+ *
+ * For subscriptions with wildcards, the subscription manager loops through the
+ * wildcard subscriptions and selects candidates that satisfy condition
+ * (publishedTopicHash & subscribedTopicMask) == subscribedTopicHash (point 2).
+ * The loop could exit early if wildcard subscriptions were stored into a sorted
+ * dictionary (utilizing point 3), but, after testing, there does not seem to be
+ * any real benefit doing so.
+ *
+ * Other considerations
+ * --------------------
+ * Characters in the topic string are cast to byte and any additional bytes in a
+ * multi-byte character are disregarded. Best guess is that this does not impact
+ * performance in practice.
+ *
+ * Instead of one-byte checksums per topic level, one-word checksums per topic
+ * level could be used. If most topics contained four levels or less then hash
+ * buckets would be shallower.
+ *
+ * For very large numbers of topics, performing a parallel search may help further.
+ *
+ * To also handle a larger number of subscribers, it may be beneficial to maintain
+ * a subscribers-by-subscription-topic dictionary.
+ */
+public static class MqttTopicHash
 {
-    /*
-    * The MqttSubscription object stores subscription parameters and calculates 
-    * topic hashes.
-    *
-    * Use of Topic Hashes to improve message processing performance
-    * =============================================================
-    * 
-    * Motivation
-    * -----------
-    * In a typical use case for MQTT there may be many publishers (sensors or 
-    * other devices in the field) and few subscribers (monitoring all or many topics).
-    * Each publisher may have one or more topic(s) to publish and therefore both, the 
-    * number of publishers and the number of topics may be large.
-    * 
-    * Maintaining subscribers in a separate container
-    * -----------------------------------------------
-    * Instead of placing all sessions into a single _sessions container, subscribers 
-    * are added into another _subscriberSessions container (if a client is a
-    * subscriber and a publisher then the client is present in both containers). The
-    * cost is some additional bookkeeping work upon subscription where each client 
-    * session needs to maintain a list of subscribed topics.
-    * 
-    * When the client subscribes to the first topic, then the session manager adds
-    * the client to the _subscriberSessions container, and when the client 
-    * unsubscribes from the last topic then the session manager removes the client
-    * from the container. Now, when an application message arrives, only the list of
-    * subscribers need processing instead of looping through potentially thousands of
-    * publishers.
-    * 
-    * Improving subscriber topic lookup
-    * ---------------------------------
-    * For each subscriber, it needs to be determined whether an application message 
-    * matches any topic the subscriber has subscribed to. There may only be few 
-    * subscribers but there may be many subscribed topics, including wildcard topics.
-    * 
-    * The implemented approach uses a topic hash and a hash mask calculated on the
-    * subscribed topic and the published topic (the application message topic) to 
-    * find candidates for a match, with the existing match logic evaluating a reduced
-    * number of candidates.
-    * 
-    * For each subscription, the topic hash and a hash mask is stored with the
-    * subscription, and for each application message received, the hash is calculated
-    * for the published topic before attempting to find matching subscriptions. The
-    * hash calculation itself is simple and does not have a large performance impact.
-    * 
-    * We'll first explain how topic hashes and hash masks are constructed and then how
-    * they are used.
-    * 
-    * Topic hash
-    * ----------
-    * Topic hashes are stored as 64-bit numbers. Each byte within the 64-bit number
-    * relates to one MQTT topic level. A checksum is calculated for each topic level
-    * by iterating over the characters within the topic level (cast to byte) and the
-    * result is stored into the corresponding byte of the 64-bit number. If a topic
-    * level contains a wildcard character, then 0x00 is stored instead of the
-    * checksum.
-    * 
-    * If there are less than 8 levels then the rest of the 64-bit number is filled
-    * with 0xff. If there are more than 8 levels then topics where the first 8 MQTT
-    * topic levels are identical will have the same hash value.
-    * 
-    * This is the topic hash for the MQTT topic below: 0x655D4AF1FFFFFF
-    * 
-    * client1/building1/level1/sensor1 (empty) (empty) (empty) (empty)
-    * \_____/ \_______/ \____/ \_____/ \_____/ \_____/ \_____/ \_____/
-    *    |        |       |       |       |       |       |       |
-    *   0x65     0x5D    0x4A   0xF1     0xFF    0xFF    0xFF    0xFF
-    * 
-    * This is the topic hash for an MQTT topic containing a wildcard: 0x655D00F1FFFFFF
-    * 
-    * client1/building1/ + /sensor1 (empty) (empty) (empty) (empty)
-    * \_____/ \_______/ \_/ \_____/ \_____/ \_____/ \_____/ \_____/
-    *    |        |      |     |       |       |       |       |
-    *   0x65     0x5D    0    0xF1    0xFF    0xFF    0xFF    0xFF
-    * 
-    * For topics that contain the multi level wildcard # at the end, the topic hash
-    * is filled with 0x00: 0x65004A00000000
-    * 
-    * client1/ + /level1/ #  (empty) (empty) (empty) (empty)
-    * \_____/ \_/ \____/ \_/ \_____/ \_____/ \_____/ \_____/
-    *    |     |    |     |     |       |       |       |
-    *   0x65   0   0x4A   0     0       0       0       0
-    * 
-    * 
-    * Topic hash mask
-    * ---------------
-    * The hash mask simply contains 0xFF for non-wildcard topic levels and 0x00 for
-    * wildcard topic levels. Here are the topic hash masks for the examples above.
-    * 
-    * client1/building1/level1/sensor1 (empty) (empty) (empty) (empty)
-    * \_____/ \_______/ \____/ \_____/ \_____/ \_____/ \_____/ \_____/
-    *    |        |       |       |       |       |       |       |
-    *   0xFF     0xFF    0xFF   0xFF     0xFF    0xFF    0xFF    0xFF
-    * 
-    * client1/building1/ + /sensor1 (empty) (empty) (empty) (empty)
-    * \_____/ \_______/ \_/ \_____/ \_____/ \_____/ \_____/ \_____/
-    *    |        |      |     |       |       |       |       |
-    *   0xFF     0xFF    0    0xFF    0xFF    0xFF    0xFF    0xFF
-    * 
-    * client1/ + /level1/ #  (empty) (empty) (empty) (empty)
-    * \_____/ \_/ \____/ \_/ \_____/ \_____/ \_____/ \_____/
-    *    |     |    |     |     |       |       |       |
-    *   0xFF   0    0xFF  0     0       0       0       0
-    * 
-    * 
-    * Topic hash and hash mask properties
-    * -----------------------------------
-    * The following properties of topic hashes and hash masks can be exploited to
-    * find potentially matching subscribed topics for a given published topic.
-    * 
-    * (1) If a subscribed topic does not contain wildcards then the topic hash of the
-    * subscribed topic must be equal to the topic hash of the published topic,
-    * otherwise the subscribed topic cannot be a candidate for a match.
-    * 
-    * (2) If a subscribed topic contains wildcards then the hash of the published
-    * topic masked with the subscribed topic's hash mask must be equal to the hash of
-    * the subscribed topic. I.e. a subscribed topic is a candidate for a match if:
-    * (publishedTopicHash & subscribedTopicHashMask) == subscribedTopicHash
-    * 
-    * (3) If a subscribed topic contains wildcards then any potentially matching
-    * published topic must have a hash value that is greater than or equal to the
-    * hash value of the subscribed topic (because the subscribed topic contains
-    * zeroes in wildcard positions).
-    * 
-    * Match finding
-    * -------------
-    * The subscription manager maintains two separate dictionaries to assist finding
-    * matches using topic hashes: a _noWildcardSubscriptionsByTopicHash dictionary
-    * containing all subscriptions that do not have wildcards, and a
-    * _wildcardSubscriptionsByTopicHash dictionary containing subscriptions with
-    * wildcards.
-    * 
-    * For subscriptions without wildcards, all potential candidates for a match are
-    * obtained by a single look-up (exploiting point 1 above).
-    * 
-    * For subscriptions with wildcards, the subscription manager loops through the
-    * wildcard subscriptions and selects candidates that satisfy condition 
-    * (publishedTopicHash & subscribedTopicMask) == subscribedTopicHash (point 2).
-    * The loop could exit early if wildcard subscriptions were stored into a sorted
-    * dictionary (utilizing point 3), but, after testing, there does not seem to be
-    * any real benefit doing so.
-    * 
-    * Other considerations
-    * --------------------
-    * Characters in the topic string are cast to byte and any additional bytes in a
-    * multi-byte character are disregarded. Best guess is that this does not impact
-    * performance in practice.
-    * 
-    * Instead of one-byte checksums per topic level, one-word checksums per topic
-    * level could be used. If most topics contained four levels or less then hash
-    * buckets would be shallower.
-    * 
-    * For very large numbers of topics, performing a parallel search may help further.
-    * 
-    * To also handle a larger number of subscribers, it may be beneficial to maintain
-    * a subscribers-by-subscription-topic dictionary.
-    */
-    public static class MqttTopicHash
+    public static void Calculate(string topic, out ulong resultHash, out ulong resultHashMask, out bool resultHasWildcard)
     {
-        public static void Calculate(string topic, out ulong resultHash, out ulong resultHashMask, out bool resultHasWildcard)
+        // calculate topic hash
+        ulong hash = 0;
+        ulong hashMaskInverted = 0;
+        ulong levelBitMask = 0;
+        ulong fillLevelBitMask = 0;
+        var hasWildcard = false;
+        byte checkSum = 0;
+        var level = 0;
+
+        var i = 0;
+        while (i < topic.Length)
         {
-            // calculate topic hash
-            ulong hash = 0;
-            ulong hashMaskInverted = 0;
-            ulong levelBitMask = 0;
-            ulong fillLevelBitMask = 0;
-            var hasWildcard = false;
-            byte checkSum = 0;
-            var level = 0;
-
-            var i = 0;
-            while (i < topic.Length)
-            {
-                var c = topic[i];
-                if (c == MqttTopicFilterComparer.LevelSeparator)
-                {
-                    // done with this level
-                    hash <<= 8;
-                    hash |= checkSum;
-                    hashMaskInverted <<= 8;
-                    hashMaskInverted |= levelBitMask;
-                    checkSum = 0;
-                    levelBitMask = 0;
-                    ++level;
-                    if (level >= 8)
-                    {
-                        break;
-                    }
-                }
-                else if (c == MqttTopicFilterComparer.SingleLevelWildcard)
-                {
-                    levelBitMask = 0xff;
-                    hasWildcard = true;
-                }
-                else if (c == MqttTopicFilterComparer.MultiLevelWildcard)
-                {
-                    // checksum is zero for a valid topic
-                    levelBitMask = 0xff;
-                    // fill rest with this fillLevelBitMask
-                    fillLevelBitMask = 0xff;
-                    hasWildcard = true;
-                    break;
-                }
-                else
-                {
-                    // The checksum should be designed to reduce the hash bucket depth for the expected
-                    // fairly regularly named MQTT topics that don't differ much,
-                    // i.e. "room1/sensor1"
-                    //      "room1/sensor2"
-                    //      "room1/sensor3"
-                    // etc.
-                    if ((c & 1) == 0)
-                    {
-                        checkSum += (byte)c;
-                    }
-                    else
-                    {
-                        checkSum ^= (byte)(c >> 1);
-                    }
-                }
-
-                ++i;
-            }
-
-            // Shift hash left and leave zeroes to fill ulong
-            if (level < 8)
+            var c = topic[i];
+            if (c == MqttTopicFilterComparer.LevelSeparator)
             {
+                // done with this level
                 hash <<= 8;
                 hash |= checkSum;
                 hashMaskInverted <<= 8;
                 hashMaskInverted |= levelBitMask;
+                checkSum = 0;
+                levelBitMask = 0;
                 ++level;
-                while (level < 8)
+                if (level >= 8)
                 {
-                    hash <<= 8;
-                    hashMaskInverted <<= 8;
-                    hashMaskInverted |= fillLevelBitMask;
-                    ++level;
+                    break;
                 }
             }
-
-            if (!hasWildcard)
+            else if (c == MqttTopicFilterComparer.SingleLevelWildcard)
             {
-                while (i < topic.Length)
+                levelBitMask = 0xff;
+                hasWildcard = true;
+            }
+            else if (c == MqttTopicFilterComparer.MultiLevelWildcard)
+            {
+                // checksum is zero for a valid topic
+                levelBitMask = 0xff;
+                // fill rest with this fillLevelBitMask
+                fillLevelBitMask = 0xff;
+                hasWildcard = true;
+                break;
+            }
+            else
+            {
+                // The checksum should be designed to reduce the hash bucket depth for the expected
+                // fairly regularly named MQTT topics that don't differ much,
+                // i.e. "room1/sensor1"
+                //      "room1/sensor2"
+                //      "room1/sensor3"
+                // etc.
+                if ((c & 1) == 0)
                 {
-                    var c = topic[i];
-                    if (c == MqttTopicFilterComparer.SingleLevelWildcard || c == MqttTopicFilterComparer.MultiLevelWildcard)
-                    {
-                        hasWildcard = true;
-                        break;
-                    }
-
-                    ++i;
+                    checkSum += (byte)c;
+                }
+                else
+                {
+                    checkSum ^= (byte)(c >> 1);
                 }
             }
 
-            resultHash = hash;
-            resultHashMask = ~hashMaskInverted;
-            resultHasWildcard = hasWildcard;
+            ++i;
         }
+
+        // Shift hash left and leave zeroes to fill ulong
+        if (level < 8)
+        {
+            hash <<= 8;
+            hash |= checkSum;
+            hashMaskInverted <<= 8;
+            hashMaskInverted |= levelBitMask;
+            ++level;
+            while (level < 8)
+            {
+                hash <<= 8;
+                hashMaskInverted <<= 8;
+                hashMaskInverted |= fillLevelBitMask;
+                ++level;
+            }
+        }
+
+        if (!hasWildcard)
+        {
+            while (i < topic.Length)
+            {
+                var c = topic[i];
+                if (c == MqttTopicFilterComparer.SingleLevelWildcard || c == MqttTopicFilterComparer.MultiLevelWildcard)
+                {
+                    hasWildcard = true;
+                    break;
+                }
+
+                ++i;
+            }
+        }
+
+        resultHash = hash;
+        resultHashMask = ~hashMaskInverted;
+        resultHasWildcard = hasWildcard;
     }
 }

Source/MQTTnet.Server/Internal/SubscribeResult.cs

@@ -5,23 +5,22 @@
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class SubscribeResult
 {
-    public sealed class SubscribeResult
+    public SubscribeResult(int topicsCount)
     {
-        public SubscribeResult(int topicsCount)
-        {
-            ReasonCodes = new List<MqttSubscribeReasonCode>(topicsCount);
-        }
-        
-        public bool CloseConnection { get; set; }
-        
-        public List<MqttSubscribeReasonCode> ReasonCodes { get; set; }
-
-        public string ReasonString { get; set; }
-
-        public List<MqttRetainedMessageMatch> RetainedMessages { get; set; }
-
-        public List<MqttUserProperty> UserProperties { get; set; }
+        ReasonCodes = new List<MqttSubscribeReasonCode>(topicsCount);
     }
+
+    public bool CloseConnection { get; set; }
+
+    public List<MqttSubscribeReasonCode> ReasonCodes { get; set; }
+
+    public string ReasonString { get; set; }
+
+    public List<MqttRetainedMessageMatch> RetainedMessages { get; set; }
+
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/Internal/TopicHashMaskSubscriptions.cs

@@ -1,31 +1,30 @@
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+/// <summary>
+///     Helper class that stores subscriptions by their topic hash mask.
+/// </summary>
+public sealed class TopicHashMaskSubscriptions
 {
-    /// <summary>
-    ///     Helper class that stores subscriptions by their topic hash mask.
-    /// </summary>
-    public sealed class TopicHashMaskSubscriptions
+    public Dictionary<ulong, HashSet<MqttSubscription>> SubscriptionsByHashMask { get; } = new Dictionary<ulong, HashSet<MqttSubscription>>();
+
+    public void AddSubscription(MqttSubscription subscription)
     {
-        public Dictionary<ulong, HashSet<MqttSubscription>> SubscriptionsByHashMask { get; } = new Dictionary<ulong, HashSet<MqttSubscription>>();
-
-        public void AddSubscription(MqttSubscription subscription)
+        if (!SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
         {
-            if (!SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
-            {
-                subscriptions = new HashSet<MqttSubscription>();
-                SubscriptionsByHashMask.Add(subscription.TopicHashMask, subscriptions);
-            }
-            subscriptions.Add(subscription);
+            subscriptions = new HashSet<MqttSubscription>();
+            SubscriptionsByHashMask.Add(subscription.TopicHashMask, subscriptions);
         }
+        subscriptions.Add(subscription);
+    }
 
-        public void RemoveSubscription(MqttSubscription subscription)
+    public void RemoveSubscription(MqttSubscription subscription)
+    {
+        if (SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
         {
-            if (SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
+            subscriptions.Remove(subscription);
+            if (subscriptions.Count == 0)
             {
-                subscriptions.Remove(subscription);
-                if (subscriptions.Count == 0)
-                {
-                    SubscriptionsByHashMask.Remove(subscription.TopicHashMask);
-                }
+                SubscriptionsByHashMask.Remove(subscription.TopicHashMask);
             }
         }
     }

Source/MQTTnet.Server/Internal/UnsubscribeResult.cs

@@ -5,14 +5,13 @@
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server.Internal
+namespace MQTTnet.Server.Internal;
+
+public sealed class UnsubscribeResult
 {
-    public sealed class UnsubscribeResult
-    {
-        public List<MqttUnsubscribeReasonCode> ReasonCodes { get; } = new List<MqttUnsubscribeReasonCode>(128);
+    public List<MqttUnsubscribeReasonCode> ReasonCodes { get; } = new List<MqttUnsubscribeReasonCode>(128);
 
-        public bool CloseConnection { get; set; }
+    public bool CloseConnection { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; set; }
-    }
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/MqttServerExtensions.cs

@@ -29,9 +29,9 @@ public static class MqttServerExtensions
         ArgumentNullException.ThrowIfNull(topic);
 
         var payloadBuffer = EmptyBuffer.Array;
-        if (payload is string stringPayload)
+        if (payload != null)
         {
-            payloadBuffer = Encoding.UTF8.GetBytes(stringPayload);
+            payloadBuffer = Encoding.UTF8.GetBytes(payload);
         }
 
         return server.InjectApplicationMessage(

Source/MQTTnet.Server/MqttServerFactory.cs

@@ -21,10 +21,7 @@ public sealed class MqttServerFactory
 
     public IMqttNetLogger DefaultLogger { get; }
 
-    public IList<Func<MqttServerFactory, IMqttServerAdapter>> DefaultServerAdapters { get; } = new List<Func<MqttServerFactory, IMqttServerAdapter>>
-    {
-        factory => new MqttTcpServerAdapter()
-    };
+    public IList<Func<MqttServerFactory, IMqttServerAdapter>> DefaultServerAdapters { get; } = [_ => new MqttTcpServerAdapter()];
 
     public IDictionary<object, object> Properties { get; } = new Dictionary<object, object>();
 

Source/MQTTnet.Server/Options/IMqttServerCertificateCredentials.cs

@@ -2,10 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public interface IMqttServerCertificateCredentials
 {
-    public interface IMqttServerCertificateCredentials
-    {
-        string Password { get; }
-    }
-}
+    string Password { get; }
+}

Source/MQTTnet.Server/Options/MqttPendingMessagesOverflowStrategy.cs

@@ -2,12 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Server
-{
-    public enum MqttPendingMessagesOverflowStrategy
-    {
-        DropOldestQueuedMessage,
+namespace MQTTnet.Server;
 
-        DropNewMessage
-    }
-}
+public enum MqttPendingMessagesOverflowStrategy
+{
+    DropOldestQueuedMessage,
+
+    DropNewMessage
+}

Source/MQTTnet.Server/Options/MqttServerCertificateCredentials.cs

@@ -2,10 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public class MqttServerCertificateCredentials : IMqttServerCertificateCredentials
 {
-    public class MqttServerCertificateCredentials : IMqttServerCertificateCredentials
-    {
-        public string Password { get; set; }
-    }
-}
+    public string Password { get; set; }
+}

Source/MQTTnet.Server/Options/MqttServerKeepAliveOptions.cs

@@ -2,20 +2,17 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class MqttServerKeepAliveOptions
 {
-    public sealed class MqttServerKeepAliveOptions
-    {
-        /// <summary>
-        ///     When this mode is enabled the MQTT server will not close a connection when the
-        ///     client is currently sending a (large) payload. This may lead to "dead" connections
-        ///     When this mode is disabled the MQTT server will disconnect a client when the keep
-        ///     alive timeout is reached even if the client is currently sending a (large) payload.
-        /// </summary>
-        public bool DisconnectClientWhenReadingPayload { get; set; }
+    /// <summary>
+    ///     When this mode is enabled the MQTT server will not close a connection when the
+    ///     client is currently sending a (large) payload. This may lead to "dead" connections
+    ///     When this mode is disabled the MQTT server will disconnect a client when the keep
+    ///     alive timeout is reached even if the client is currently sending a (large) payload.
+    /// </summary>
+    public bool DisconnectClientWhenReadingPayload { get; set; }
 
-        public TimeSpan MonitorInterval { get; set; } = TimeSpan.FromMilliseconds(500);
-    }
+    public TimeSpan MonitorInterval { get; set; } = TimeSpan.FromMilliseconds(500);
 }

Source/MQTTnet.Server/Options/MqttServerOptionsBuilder.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Net;
 using System.Net.Security;
 using System.Security.Authentication;
@@ -10,207 +9,206 @@ using MQTTnet.Certificates;
 using System.Security.Cryptography.X509Certificates;
 
 // ReSharper disable UnusedMember.Global
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public class MqttServerOptionsBuilder
 {
-    public class MqttServerOptionsBuilder
+    readonly MqttServerOptions _options = new();
+
+    public MqttServerOptions Build()
     {
-        readonly MqttServerOptions _options = new MqttServerOptions();
+        return _options;
+    }
 
-        public MqttServerOptions Build()
+    public MqttServerOptionsBuilder WithClientCertificate(RemoteCertificateValidationCallback validationCallback = null, bool checkCertificateRevocation = false)
+    {
+        _options.TlsEndpointOptions.ClientCertificateRequired = true;
+        _options.TlsEndpointOptions.CheckCertificateRevocation = checkCertificateRevocation;
+        _options.TlsEndpointOptions.RemoteCertificateValidationCallback = validationCallback;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithConnectionBacklog(int value)
+    {
+        _options.DefaultEndpointOptions.ConnectionBacklog = value;
+        _options.TlsEndpointOptions.ConnectionBacklog = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithDefaultCommunicationTimeout(TimeSpan value)
+    {
+        _options.DefaultCommunicationTimeout = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithDefaultEndpoint()
+    {
+        _options.DefaultEndpointOptions.IsEnabled = true;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithDefaultEndpointBoundIPAddress(IPAddress value)
+    {
+        _options.DefaultEndpointOptions.BoundInterNetworkAddress = value ?? IPAddress.Any;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithDefaultEndpointBoundIPV6Address(IPAddress value)
+    {
+        _options.DefaultEndpointOptions.BoundInterNetworkV6Address = value ?? IPAddress.Any;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithDefaultEndpointPort(int value)
+    {
+        _options.DefaultEndpointOptions.Port = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithDefaultEndpointReuseAddress()
+    {
+        _options.DefaultEndpointOptions.ReuseAddress = true;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptedEndpoint()
+    {
+        _options.TlsEndpointOptions.IsEnabled = true;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptedEndpointBoundIPAddress(IPAddress value)
+    {
+        _options.TlsEndpointOptions.BoundInterNetworkAddress = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptedEndpointBoundIPV6Address(IPAddress value)
+    {
+        _options.TlsEndpointOptions.BoundInterNetworkV6Address = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptedEndpointPort(int value)
+    {
+        _options.TlsEndpointOptions.Port = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptionSslProtocol(SslProtocols value)
+    {
+        _options.TlsEndpointOptions.SslProtocol = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithKeepAlive()
+    {
+        _options.DefaultEndpointOptions.KeepAlive = true;
+        _options.TlsEndpointOptions.KeepAlive = true;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithMaxPendingMessagesPerClient(int value)
+    {
+        _options.MaxPendingMessagesPerClient = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithPendingMessagesOverflowStrategy(MqttPendingMessagesOverflowStrategy value)
+    {
+        _options.PendingMessagesOverflowStrategy = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithoutDefaultEndpoint()
+    {
+        _options.DefaultEndpointOptions.IsEnabled = false;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithoutEncryptedEndpoint()
+    {
+        _options.TlsEndpointOptions.IsEnabled = false;
+        return this;
+    }
+
+    /// <summary>
+    ///     Usually the MQTT packets can be send partially to improve memory allocations.
+    ///     This is done by using multiple TCP packets or WebSocket frames etc.
+    ///     Unfortunately not all clients do support this and will close the connection when receiving partial packets.
+    /// </summary>
+    public MqttServerOptionsBuilder WithoutPacketFragmentation()
+    {
+        _options.DefaultEndpointOptions.AllowPacketFragmentation = false;
+        _options.TlsEndpointOptions.AllowPacketFragmentation = false;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithPersistentSessions(bool value = true)
+    {
+        _options.EnablePersistentSessions = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithRemoteCertificateValidationCallback(RemoteCertificateValidationCallback value)
+    {
+        _options.TlsEndpointOptions.RemoteCertificateValidationCallback = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithTcpKeepAliveInterval(int value)
+    {
+        _options.DefaultEndpointOptions.TcpKeepAliveInterval = value;
+        _options.TlsEndpointOptions.TcpKeepAliveInterval = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithTcpKeepAliveRetryCount(int value)
+    {
+        _options.DefaultEndpointOptions.TcpKeepAliveRetryCount = value;
+        _options.TlsEndpointOptions.TcpKeepAliveRetryCount = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithTcpKeepAliveTime(int value)
+    {
+        _options.DefaultEndpointOptions.TcpKeepAliveTime = value;
+        _options.TlsEndpointOptions.TcpKeepAliveTime = value;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithTlsEndpointReuseAddress()
+    {
+        _options.TlsEndpointOptions.ReuseAddress = true;
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptionCertificate(byte[] value, IMqttServerCertificateCredentials credentials = null)
+    {
+        ArgumentNullException.ThrowIfNull(value);
+
+        _options.TlsEndpointOptions.CertificateProvider = new BlobCertificateProvider(value)
         {
-            return _options;
-        }
+            Password = credentials?.Password
+        };
 
-        public MqttServerOptionsBuilder WithClientCertificate(RemoteCertificateValidationCallback validationCallback = null, bool checkCertificateRevocation = false)
-        {
-            _options.TlsEndpointOptions.ClientCertificateRequired = true;
-            _options.TlsEndpointOptions.CheckCertificateRevocation = checkCertificateRevocation;
-            _options.TlsEndpointOptions.RemoteCertificateValidationCallback = validationCallback;
-            return this;
-        }
+        return this;
+    }
 
-        public MqttServerOptionsBuilder WithConnectionBacklog(int value)
-        {
-            _options.DefaultEndpointOptions.ConnectionBacklog = value;
-            _options.TlsEndpointOptions.ConnectionBacklog = value;
-            return this;
-        }
+    public MqttServerOptionsBuilder WithEncryptionCertificate(X509Certificate2 certificate)
+    {
+        ArgumentNullException.ThrowIfNull(certificate);
 
-        public MqttServerOptionsBuilder WithDefaultCommunicationTimeout(TimeSpan value)
-        {
-            _options.DefaultCommunicationTimeout = value;
-            return this;
-        }
+        _options.TlsEndpointOptions.CertificateProvider = new X509CertificateProvider(certificate);
+        return this;
+    }
 
-        public MqttServerOptionsBuilder WithDefaultEndpoint()
-        {
-            _options.DefaultEndpointOptions.IsEnabled = true;
-            return this;
-        }
+    public MqttServerOptionsBuilder WithEncryptionCertificate(ICertificateProvider certificateProvider)
+    {
+        ArgumentNullException.ThrowIfNull(certificateProvider);
 
-        public MqttServerOptionsBuilder WithDefaultEndpointBoundIPAddress(IPAddress value)
-        {
-            _options.DefaultEndpointOptions.BoundInterNetworkAddress = value ?? IPAddress.Any;
-            return this;
-        }
+        _options.TlsEndpointOptions.CertificateProvider = certificateProvider;
 
-        public MqttServerOptionsBuilder WithDefaultEndpointBoundIPV6Address(IPAddress value)
-        {
-            _options.DefaultEndpointOptions.BoundInterNetworkV6Address = value ?? IPAddress.Any;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithDefaultEndpointPort(int value)
-        {
-            _options.DefaultEndpointOptions.Port = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithDefaultEndpointReuseAddress()
-        {
-            _options.DefaultEndpointOptions.ReuseAddress = true;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptedEndpoint()
-        {
-            _options.TlsEndpointOptions.IsEnabled = true;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptedEndpointBoundIPAddress(IPAddress value)
-        {
-            _options.TlsEndpointOptions.BoundInterNetworkAddress = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptedEndpointBoundIPV6Address(IPAddress value)
-        {
-            _options.TlsEndpointOptions.BoundInterNetworkV6Address = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptedEndpointPort(int value)
-        {
-            _options.TlsEndpointOptions.Port = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptionSslProtocol(SslProtocols value)
-        {
-            _options.TlsEndpointOptions.SslProtocol = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithKeepAlive()
-        {
-            _options.DefaultEndpointOptions.KeepAlive = true;
-            _options.TlsEndpointOptions.KeepAlive = true;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithMaxPendingMessagesPerClient(int value)
-        {
-            _options.MaxPendingMessagesPerClient = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithPendingMessagesOverflowStrategy(MqttPendingMessagesOverflowStrategy value)
-        {
-            _options.PendingMessagesOverflowStrategy = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithoutDefaultEndpoint()
-        {
-            _options.DefaultEndpointOptions.IsEnabled = false;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithoutEncryptedEndpoint()
-        {
-            _options.TlsEndpointOptions.IsEnabled = false;
-            return this;
-        }
-
-        /// <summary>
-        ///     Usually the MQTT packets can be send partially to improve memory allocations.
-        ///     This is done by using multiple TCP packets or WebSocket frames etc.
-        ///     Unfortunately not all clients do support this and will close the connection when receiving partial packets.
-        /// </summary>
-        public MqttServerOptionsBuilder WithoutPacketFragmentation()
-        {
-            _options.DefaultEndpointOptions.AllowPacketFragmentation = false;
-            _options.TlsEndpointOptions.AllowPacketFragmentation = false;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithPersistentSessions(bool value = true)
-        {
-            _options.EnablePersistentSessions = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithRemoteCertificateValidationCallback(RemoteCertificateValidationCallback value)
-        {
-            _options.TlsEndpointOptions.RemoteCertificateValidationCallback = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithTcpKeepAliveInterval(int value)
-        {
-            _options.DefaultEndpointOptions.TcpKeepAliveInterval = value;
-            _options.TlsEndpointOptions.TcpKeepAliveInterval = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithTcpKeepAliveRetryCount(int value)
-        {
-            _options.DefaultEndpointOptions.TcpKeepAliveRetryCount = value;
-            _options.TlsEndpointOptions.TcpKeepAliveRetryCount = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithTcpKeepAliveTime(int value)
-        {
-            _options.DefaultEndpointOptions.TcpKeepAliveTime = value;
-            _options.TlsEndpointOptions.TcpKeepAliveTime = value;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithTlsEndpointReuseAddress()
-        {
-            _options.TlsEndpointOptions.ReuseAddress = true;
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptionCertificate(byte[] value, IMqttServerCertificateCredentials credentials = null)
-        {
-            ArgumentNullException.ThrowIfNull(value);
-
-            _options.TlsEndpointOptions.CertificateProvider = new BlobCertificateProvider(value)
-            {
-                Password = credentials?.Password
-            };
-
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptionCertificate(X509Certificate2 certificate)
-        {
-            ArgumentNullException.ThrowIfNull(certificate);
-
-            _options.TlsEndpointOptions.CertificateProvider = new X509CertificateProvider(certificate);
-            return this;
-        }
-
-        public MqttServerOptionsBuilder WithEncryptionCertificate(ICertificateProvider certificateProvider)
-        {
-            ArgumentNullException.ThrowIfNull(certificateProvider);
-
-            _options.TlsEndpointOptions.CertificateProvider = certificateProvider;
-
-            return this;
-        }
+        return this;
     }
 }

Source/MQTTnet.Server/Options/MqttServerTcpEndpointBaseOptions.cs

@@ -5,59 +5,58 @@
 using System.Net;
 using System.Net.Sockets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public abstract class MqttServerTcpEndpointBaseOptions
 {
-    public abstract class MqttServerTcpEndpointBaseOptions
-    {
-        public bool IsEnabled { get; set; }
+    public bool IsEnabled { get; set; }
 
-        public int Port { get; set; }
+    public int Port { get; set; }
 
-        public int ConnectionBacklog { get; set; } = 100;
+    public int ConnectionBacklog { get; set; } = 100;
 
-        public bool NoDelay { get; set; } = true;
+    public bool NoDelay { get; set; } = true;
 
-        /// <summary>
-        ///     Gets or sets whether the sockets keep alive feature should be used.
-        ///     The value _null_ indicates that the OS and framework defaults should be used.
-        /// </summary>
-        public bool? KeepAlive { get; set; }
+    /// <summary>
+    ///     Gets or sets whether the sockets keep alive feature should be used.
+    ///     The value _null_ indicates that the OS and framework defaults should be used.
+    /// </summary>
+    public bool? KeepAlive { get; set; }
 
-        /// <summary>
-        ///     Usually the MQTT packets can be send partially. This is done by using multiple TCP packets
-        ///     or WebSocket frames etc. Unfortunately not all clients do support this feature and
-        ///     will close the connection when receiving such packets. If such clients are connecting to this
-        ///     server the flag must be set to _false_.
-        /// </summary>
-        public bool AllowPacketFragmentation { get; set; } = true;
+    /// <summary>
+    ///     Usually the MQTT packets can be send partially. This is done by using multiple TCP packets
+    ///     or WebSocket frames etc. Unfortunately not all clients do support this feature and
+    ///     will close the connection when receiving such packets. If such clients are connecting to this
+    ///     server the flag must be set to _false_.
+    /// </summary>
+    public bool AllowPacketFragmentation { get; set; } = true;
 
-        /// <summary>
-        ///     Gets or sets the TCP keep alive interval.
-        ///     The value _null_ indicates that the OS and framework defaults should be used.
-        /// </summary>
-        public int? TcpKeepAliveInterval { get; set; }
+    /// <summary>
+    ///     Gets or sets the TCP keep alive interval.
+    ///     The value _null_ indicates that the OS and framework defaults should be used.
+    /// </summary>
+    public int? TcpKeepAliveInterval { get; set; }
 
-        /// <summary>
-        ///     Gets or sets the TCP keep alive retry count.
-        ///     The value _null_ indicates that the OS and framework defaults should be used.
-        /// </summary>
-        public int? TcpKeepAliveRetryCount { get; set; }
+    /// <summary>
+    ///     Gets or sets the TCP keep alive retry count.
+    ///     The value _null_ indicates that the OS and framework defaults should be used.
+    /// </summary>
+    public int? TcpKeepAliveRetryCount { get; set; }
 
-        /// <summary>
-        ///     Gets or sets the TCP keep alive time.
-        ///     The value _null_ indicates that the OS and framework defaults should be used.
-        /// </summary>
-        public int? TcpKeepAliveTime { get; set; }
+    /// <summary>
+    ///     Gets or sets the TCP keep alive time.
+    ///     The value _null_ indicates that the OS and framework defaults should be used.
+    /// </summary>
+    public int? TcpKeepAliveTime { get; set; }
 
-        public LingerOption LingerState { get; set; } = new LingerOption(true, 0);
+    public LingerOption LingerState { get; set; } = new LingerOption(true, 0);
 
-        public IPAddress BoundInterNetworkAddress { get; set; } = IPAddress.Any;
+    public IPAddress BoundInterNetworkAddress { get; set; } = IPAddress.Any;
 
-        public IPAddress BoundInterNetworkV6Address { get; set; } = IPAddress.IPv6Any;
+    public IPAddress BoundInterNetworkV6Address { get; set; } = IPAddress.IPv6Any;
 
-        /// <summary>
-        ///     This requires admin permissions on Linux.
-        /// </summary>
-        public bool ReuseAddress { get; set; }
-    }
+    /// <summary>
+    ///     This requires admin permissions on Linux.
+    /// </summary>
+    public bool ReuseAddress { get; set; }
 }

Source/MQTTnet.Server/Options/MqttServerTcpEndpointOptions.cs

@@ -2,13 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public class MqttServerTcpEndpointOptions : MqttServerTcpEndpointBaseOptions
 {
-    public class MqttServerTcpEndpointOptions : MqttServerTcpEndpointBaseOptions
+    public MqttServerTcpEndpointOptions()
     {
-        public MqttServerTcpEndpointOptions()
-        {
-            Port = 1883;
-        }
+        Port = 1883;
     }
-}
+}

Source/MQTTnet.Server/Options/MqttServerTlsTcpEndpointOptions.cs

@@ -5,29 +5,28 @@
 using System.Security.Authentication;
 using MQTTnet.Certificates;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class MqttServerTlsTcpEndpointOptions : MqttServerTcpEndpointBaseOptions
 {
-    public sealed class MqttServerTlsTcpEndpointOptions : MqttServerTcpEndpointBaseOptions
+    public MqttServerTlsTcpEndpointOptions()
     {
-        public MqttServerTlsTcpEndpointOptions()
-        {
-            Port = 8883;
-        }
-
-        public System.Net.Security.RemoteCertificateValidationCallback RemoteCertificateValidationCallback { get; set; }
-
-        public ICertificateProvider CertificateProvider { get; set; }
-
-        public bool ClientCertificateRequired { get; set; }
-
-        public bool CheckCertificateRevocation { get; set; }
-
-        /// <summary>
-        /// The default value is SslProtocols.None, which allows the operating system to choose the best protocol to use, and to block protocols that are not secure.
-        /// </summary>
-        /// <seealso href="https://learn.microsoft.com/en-us/dotnet/api/system.security.authentication.sslprotocols">SslProtocols</seealso>       
-        public SslProtocols SslProtocol { get; set; } = SslProtocols.None;
-
-        public System.Net.Security.CipherSuitesPolicy CipherSuitesPolicy { get; set; }
+        Port = 8883;
     }
-}
+
+    public System.Net.Security.RemoteCertificateValidationCallback RemoteCertificateValidationCallback { get; set; }
+
+    public ICertificateProvider CertificateProvider { get; set; }
+
+    public bool ClientCertificateRequired { get; set; }
+
+    public bool CheckCertificateRevocation { get; set; }
+
+    /// <summary>
+    /// The default value is SslProtocols.None, which allows the operating system to choose the best protocol to use, and to block protocols that are not secure.
+    /// </summary>
+    /// <seealso href="https://learn.microsoft.com/en-us/dotnet/api/system.security.authentication.sslprotocols">SslProtocols</seealso>
+    public SslProtocols SslProtocol { get; set; } = SslProtocols.None;
+
+    public System.Net.Security.CipherSuitesPolicy CipherSuitesPolicy { get; set; }
+}

Source/MQTTnet.Server/Stopping/MqttServerStopOptions.cs

@@ -4,20 +4,19 @@
 
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class MqttServerStopOptions
 {
-    public sealed class MqttServerStopOptions
+    /// <summary>
+    ///     These disconnect options are sent to every connected client via a DISCONNECT packet.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public MqttServerClientDisconnectOptions DefaultClientDisconnectOptions { get; set; } = new MqttServerClientDisconnectOptions
     {
-        /// <summary>
-        ///     These disconnect options are sent to every connected client via a DISCONNECT packet.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public MqttServerClientDisconnectOptions DefaultClientDisconnectOptions { get; set; } = new MqttServerClientDisconnectOptions
-        {
-            ReasonCode = MqttDisconnectReasonCode.ServerShuttingDown,
-            UserProperties = null,
-            ReasonString = null,
-            ServerReference = null
-        };
-    }
+        ReasonCode = MqttDisconnectReasonCode.ServerShuttingDown,
+        UserProperties = null,
+        ReasonString = null,
+        ServerReference = null
+    };
 }

Source/MQTTnet.Server/Stopping/MqttServerStopOptionsBuilder.cs

@@ -2,34 +2,31 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class MqttServerStopOptionsBuilder
 {
-    public sealed class MqttServerStopOptionsBuilder
+    readonly MqttServerStopOptions _options = new();
+
+    public MqttServerStopOptionsBuilder WithDefaultClientDisconnectOptions(MqttServerClientDisconnectOptions value)
     {
-        readonly MqttServerStopOptions _options = new MqttServerStopOptions();
+        _options.DefaultClientDisconnectOptions = value;
+        return this;
+    }
 
-        public MqttServerStopOptionsBuilder WithDefaultClientDisconnectOptions(MqttServerClientDisconnectOptions value)
-        {
-            _options.DefaultClientDisconnectOptions = value;
-            return this;
-        }
+    public MqttServerStopOptionsBuilder WithDefaultClientDisconnectOptions(Action<MqttServerClientDisconnectOptionsBuilder> builder)
+    {
+        ArgumentNullException.ThrowIfNull(builder);
 
-        public MqttServerStopOptionsBuilder WithDefaultClientDisconnectOptions(Action<MqttServerClientDisconnectOptionsBuilder> builder)
-        {
-            ArgumentNullException.ThrowIfNull(builder);
+        var optionsBuilder = new MqttServerClientDisconnectOptionsBuilder();
+        builder(optionsBuilder);
 
-            var optionsBuilder = new MqttServerClientDisconnectOptionsBuilder();
-            builder.Invoke(optionsBuilder);
+        _options.DefaultClientDisconnectOptions = optionsBuilder.Build();
+        return this;
+    }
 
-            _options.DefaultClientDisconnectOptions = optionsBuilder.Build();
-            return this;
-        }
-
-        public MqttServerStopOptions Build()
-        {
-            return _options;
-        }
+    public MqttServerStopOptions Build()
+    {
+        return _options;
     }
 }

Source/MQTTnet.Server/SubscribeResponse.cs

@@ -18,5 +18,5 @@ public sealed class SubscribeResponse
 
     public string ReasonString { get; set; }
 
-    public List<MqttUserProperty> UserProperties { get; } = new();
+    public List<MqttUserProperty> UserProperties { get; } = [];
 }

Source/MQTTnet.Server/UnsubscribeResponse.cs

@@ -17,5 +17,5 @@ public sealed class UnsubscribeResponse
 
     public string ReasonString { get; set; }
 
-    public List<MqttUserProperty> UserProperties { get; } = new();
+    public List<MqttUserProperty> UserProperties { get; } = [];
 }

Source/MQTTnet.TestApp/AsyncLockTest.cs

@@ -2,27 +2,58 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Threading;
 using System.Threading.Tasks;
-using MQTTnet.Internal;
+using MQTTnet.Exceptions;
 
-namespace MQTTnet.TestApp
+namespace MQTTnet.TestApp;
+
+public sealed class AsyncLockTest
 {
-    public sealed class AsyncLockTest
+    public async Task Run()
     {
-        public async Task Run()
+        try
         {
-            var asyncLock = new AsyncLock();
+            var semaphore = new SemaphoreSlim(1, 1);
 
-            using (var cancellationToken = new CancellationTokenSource())
+            await semaphore.WaitAsync();
+            try
             {
-                for (var i = 0; i < 100000; i++)
-                {
-                    using (await asyncLock.EnterAsync(cancellationToken.Token).ConfigureAwait(false))
-                    {
-                    }
-                } 
+                // Wait for data from socket etc...
+                // Then get an exception.
+                semaphore.Dispose();
+                throw new MqttCommunicationException("Connection closed");
+            }
+            finally
+            {
+                semaphore.Release();
             }
         }
+        catch (Exception exception)
+        {
+            Console.WriteLine(exception.ToString());
+        }
+
+
+
+
+
+
+
+
+
+
+
+
+        // var asyncLock = new AsyncLock();
+        //
+        // using var cancellationToken = new CancellationTokenSource();
+        // for (var i = 0; i < 100000; i++)
+        // {
+        //     using (await asyncLock.EnterAsync(cancellationToken.Token).ConfigureAwait(false))
+        //     {
+        //     }
+        // }
     }
 }

Source/MQTTnet.TestApp/ClientFlowTest.cs

@@ -6,49 +6,48 @@ using System;
 using System.Threading.Tasks;
 using MQTTnet.Diagnostics.Logger;
 
-namespace MQTTnet.TestApp
+namespace MQTTnet.TestApp;
+
+public static class ClientFlowTest
 {
-    public static class ClientFlowTest
+    public static async Task RunAsync()
     {
-        public static async Task RunAsync()
+        try
         {
-            try
-            {
-                var logger = new MqttNetEventLogger();
-                MqttNetConsoleLogger.ForwardToConsole(logger);
+            var logger = new MqttNetEventLogger();
+            MqttNetConsoleLogger.ForwardToConsole(logger);
 
-                var factory = new MqttClientFactory(logger);
+            var factory = new MqttClientFactory(logger);
 
-                var client = factory.CreateMqttClient();
+            var client = factory.CreateMqttClient();
 
-                var options = new MqttClientOptionsBuilder()
-                    .WithTcpServer("localhost")
-                    .Build();
+            var options = new MqttClientOptionsBuilder()
+                .WithTcpServer("localhost")
+                .Build();
 
-                Console.WriteLine("BEFORE CONNECT");
-                await client.ConnectAsync(options);
-                Console.WriteLine("AFTER CONNECT");
+            Console.WriteLine("BEFORE CONNECT");
+            await client.ConnectAsync(options);
+            Console.WriteLine("AFTER CONNECT");
 
-                Console.WriteLine("BEFORE SUBSCRIBE");
-                await client.SubscribeAsync("test/topic");
-                Console.WriteLine("AFTER SUBSCRIBE");
+            Console.WriteLine("BEFORE SUBSCRIBE");
+            await client.SubscribeAsync("test/topic");
+            Console.WriteLine("AFTER SUBSCRIBE");
 
-                Console.WriteLine("BEFORE PUBLISH");
-                await client.PublishStringAsync("test/topic", "payload");
-                Console.WriteLine("AFTER PUBLISH");
+            Console.WriteLine("BEFORE PUBLISH");
+            await client.PublishStringAsync("test/topic", "payload");
+            Console.WriteLine("AFTER PUBLISH");
 
-                await Task.Delay(1000);
+            await Task.Delay(1000);
 
-                Console.WriteLine("BEFORE DISCONNECT");
-                await client.DisconnectAsync();
-                Console.WriteLine("AFTER DISCONNECT");
+            Console.WriteLine("BEFORE DISCONNECT");
+            await client.DisconnectAsync();
+            Console.WriteLine("AFTER DISCONNECT");
 
-                Console.WriteLine("FINISHED");
-            }
-            catch (Exception ex)
-            {
-                Console.WriteLine(ex);
-            }
+            Console.WriteLine("FINISHED");
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine(ex);
         }
     }
-}
+}

Source/MQTTnet.TestApp/ClientTest.cs

@@ -10,99 +10,98 @@ using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Internal;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.TestApp
+namespace MQTTnet.TestApp;
+
+public static class ClientTest
 {
-    public static class ClientTest
+    public static async Task RunAsync()
     {
-        public static async Task RunAsync()
+        try
         {
-            try
+            var logger = new MqttNetEventLogger();
+            MqttNetConsoleLogger.ForwardToConsole(logger);
+
+            var factory = new MqttClientFactory(logger);
+            var client = factory.CreateMqttClient();
+            var clientOptions = new MqttClientOptions
             {
-                var logger = new MqttNetEventLogger();
-                MqttNetConsoleLogger.ForwardToConsole(logger);
-
-                var factory = new MqttClientFactory(logger);
-                var client = factory.CreateMqttClient();
-                var clientOptions = new MqttClientOptions
+                ChannelOptions = new MqttClientTcpOptions
                 {
-                    ChannelOptions = new MqttClientTcpOptions
-                    {
-                        RemoteEndpoint = new DnsEndPoint("127.0.0.1", 0)
-                    }
-                };
+                    RemoteEndpoint = new DnsEndPoint("127.0.0.1", 0)
+                }
+            };
 
-                client.ApplicationMessageReceivedAsync += e =>
+            client.ApplicationMessageReceivedAsync += e =>
+            {
+                var payloadText = string.Empty;
+                if (e.ApplicationMessage.Payload.Length > 0)
                 {
-                    var payloadText = string.Empty;
-                    if (e.ApplicationMessage.Payload.Length > 0)
-                    {
-                        payloadText = Encoding.UTF8.GetString(e.ApplicationMessage.Payload);
-                    }
+                    payloadText = Encoding.UTF8.GetString(e.ApplicationMessage.Payload);
+                }
 
-                    Console.WriteLine("### RECEIVED APPLICATION MESSAGE ###");
-                    Console.WriteLine($"+ Topic = {e.ApplicationMessage.Topic}");
-                    Console.WriteLine($"+ Payload = {payloadText}");
-                    Console.WriteLine($"+ QoS = {e.ApplicationMessage.QualityOfServiceLevel}");
-                    Console.WriteLine($"+ Retain = {e.ApplicationMessage.Retain}");
-                    Console.WriteLine();
+                Console.WriteLine("### RECEIVED APPLICATION MESSAGE ###");
+                Console.WriteLine($"+ Topic = {e.ApplicationMessage.Topic}");
+                Console.WriteLine($"+ Payload = {payloadText}");
+                Console.WriteLine($"+ QoS = {e.ApplicationMessage.QualityOfServiceLevel}");
+                Console.WriteLine($"+ Retain = {e.ApplicationMessage.Retain}");
+                Console.WriteLine();
 
-                    return CompletedTask.Instance;
-                };
+                return CompletedTask.Instance;
+            };
 
-                client.ConnectedAsync += async e =>
-                {
-                    Console.WriteLine("### CONNECTED WITH SERVER ###");
+            client.ConnectedAsync += async _ =>
+            {
+                Console.WriteLine("### CONNECTED WITH SERVER ###");
 
-                    await client.SubscribeAsync("#");
+                await client.SubscribeAsync("#");
 
-                    Console.WriteLine("### SUBSCRIBED ###");
-                };
+                Console.WriteLine("### SUBSCRIBED ###");
+            };
 
-                client.DisconnectedAsync += async e =>
-                {
-                    Console.WriteLine("### DISCONNECTED FROM SERVER ###");
-                    await Task.Delay(TimeSpan.FromSeconds(5));
-
-                    try
-                    {
-                        await client.ConnectAsync(clientOptions);
-                    }
-                    catch
-                    {
-                        Console.WriteLine("### RECONNECTING FAILED ###");
-                    }
-                };
+            client.DisconnectedAsync += async _ =>
+            {
+                Console.WriteLine("### DISCONNECTED FROM SERVER ###");
+                await Task.Delay(TimeSpan.FromSeconds(5));
 
                 try
                 {
                     await client.ConnectAsync(clientOptions);
                 }
-                catch (Exception exception)
+                catch
                 {
-                    Console.WriteLine("### CONNECTING FAILED ###" + Environment.NewLine + exception);
+                    Console.WriteLine("### RECONNECTING FAILED ###");
                 }
+            };
 
-                Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
-
-                while (true)
-                {
-                    Console.ReadLine();
-
-                    await client.SubscribeAsync("test");
-
-                    var applicationMessage = new MqttApplicationMessageBuilder()
-                        .WithTopic("A/B/C")
-                        .WithPayload("Hello World")
-                        .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce)
-                        .Build();
-
-                    await client.PublishAsync(applicationMessage);
-                }
+            try
+            {
+                await client.ConnectAsync(clientOptions);
             }
             catch (Exception exception)
             {
-                Console.WriteLine(exception);
+                Console.WriteLine("### CONNECTING FAILED ###" + Environment.NewLine + exception);
+            }
+
+            Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
+
+            while (true)
+            {
+                Console.ReadLine();
+
+                await client.SubscribeAsync("test");
+
+                var applicationMessage = new MqttApplicationMessageBuilder()
+                    .WithTopic("A/B/C")
+                    .WithPayload("Hello World")
+                    .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce)
+                    .Build();
+
+                await client.PublishAsync(applicationMessage);
             }
         }
+        catch (Exception exception)
+        {
+            Console.WriteLine(exception);
+        }
     }
-}
+}

Source/MQTTnet.TestApp/MessageThroughputTest.cs

@@ -1,342 +1,345 @@
 using MQTTnet.Server;
 using System.Collections.Generic;
 using System;
+using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Linq;
 using MQTTnet.Internal;
 
-namespace MQTTnet.TestApp
+namespace MQTTnet.TestApp;
+
+/// <summary>
+/// Connect a number of publisher clients and one subscriber client, then publish messages and measure
+/// the number of messages per second that can be exchanged between publishers and subscriber.
+/// Measurements are performed for subscriptions containing no wildcard, a single wildcard or multiple wildcards.
+/// </summary>
+public class MessageThroughputTest
 {
-    /// <summary>
-    /// Connect a number of publisher clients and one subscriber client, then publish messages and measure
-    /// the number of messages per second that can be exchanged between publishers and subscriber.
-    /// Measurements are performed for subscriptions containing no wildcard, a single wildcard or multiple wildcards.
-    /// </summary>
-    public class MessageThroughputTest
+    // Change these constants to suit
+    const int NumPublishers = 5000;
+    const int NumTopicsPerPublisher = 10;
+
+    // Note: Other code changes may be required when changing this constant:
+    const int NumSubscribers = 1; // Fixed
+
+    // Number of publish calls before a response for all published messages is awaited.
+    // This must be limited to a reasonable value that the server or TCP pipeline can handle.
+    const int NumPublishCallsPerBatch = 250;
+
+    // Message counters are set/reset in the PublishAllAsync loop
+    int _messagesReceivedCount;
+    int _messagesExpectedCount;
+
+    CancellationTokenSource _cancellationTokenSource;
+
+    MqttServer _mqttServer;
+    Dictionary<string, IMqttClient> _mqttPublisherClientsByPublisherName;
+    List<IMqttClient> _mqttSubscriberClients;
+
+    Dictionary<string, List<string>> _topicsByPublisher;
+    Dictionary<string, List<string>> _singleWildcardTopicsByPublisher;
+    Dictionary<string, List<string>> _multiWildcardTopicsByPublisher;
+
+    public async Task Run()
     {
-        // Change these constants to suit
-        const int NumPublishers = 5000;
-        const int NumTopicsPerPublisher = 10;
-
-        // Note: Other code changes may be required when changing this constant:
-        const int NumSubscribers = 1; // Fixed
-
-        // Number of publish calls before a response for all published messages is awaited.
-        // This must be limited to a reasonable value that the server or TCP pipeline can handle.
-        const int NumPublishCallsPerBatch = 250;
-
-        // Message counters are set/reset in the PublishAllAsync loop
-        int _messagesReceivedCount;
-        int _messagesExpectedCount;
-
-        CancellationTokenSource _cancellationTokenSource;
-
-        MqttServer _mqttServer;
-        Dictionary<string, IMqttClient> _mqttPublisherClientsByPublisherName;
-        List<IMqttClient> _mqttSubscriberClients;
-
-        Dictionary<string, List<string>> _topicsByPublisher;
-        Dictionary<string, List<string>> _singleWildcardTopicsByPublisher;
-        Dictionary<string, List<string>> _multiWildcardTopicsByPublisher;
-
-        public async Task Run()
+        try
         {
-            try
-            {
-                Console.WriteLine();
-                Console.WriteLine("Begin message throughput test");
-                Console.WriteLine();
+            Console.WriteLine();
+            Console.WriteLine("Begin message throughput test");
+            Console.WriteLine();
 
-                Console.WriteLine("Number of publishers: " + NumPublishers);
-                Console.WriteLine("Number of published topics (total): " + NumPublishers * NumTopicsPerPublisher);
-                Console.WriteLine("Number of subscribers: " + NumSubscribers);
+            Console.WriteLine("Number of publishers: " + NumPublishers);
+            Console.WriteLine("Number of published topics (total): " + NumPublishers * NumTopicsPerPublisher);
+            Console.WriteLine("Number of subscribers: " + NumSubscribers);
 
-                await Setup();
+            await Setup();
 
-                await Subscribe_to_No_Wildcard_Topics();
-                await Subscribe_to_Single_Wildcard_Topics();
-                await Subscribe_to_Multi_Wildcard_Topics();
-
-                Console.WriteLine();
-                Console.WriteLine("End message throughput test");
-            }
-            catch (Exception ex)
-            {
-                ConsoleWriteLineError(ex.Message);
-            }
-            finally
-            {
-                await Cleanup();
-            }
-        }
-
-        public async Task Setup()
-        {
-            new TopicGenerator().Generate(NumPublishers, NumTopicsPerPublisher, out _topicsByPublisher, out _singleWildcardTopicsByPublisher, out _multiWildcardTopicsByPublisher);
-
-            var serverOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
-            var mqttClientFactory = new MqttClientFactory();
-            var mqttServerFactory = new MqttServerFactory();
-            _mqttServer = mqttServerFactory.CreateMqttServer(serverOptions);
-            await _mqttServer.StartAsync();
+            await Subscribe_to_No_Wildcard_Topics();
+            await Subscribe_to_Single_Wildcard_Topics();
+            await Subscribe_to_Multi_Wildcard_Topics();
 
             Console.WriteLine();
-            Console.WriteLine("Begin connect " + NumPublishers + " publisher(s)...");
+            Console.WriteLine("End message throughput test");
+        }
+        catch (Exception ex)
+        {
+            ConsoleWriteLineError(ex.Message);
+        }
+        finally
+        {
+            await Cleanup();
+        }
+    }
 
-            var stopWatch = new System.Diagnostics.Stopwatch();
-            stopWatch.Start();
-            _mqttPublisherClientsByPublisherName = new Dictionary<string, IMqttClient>();
-            foreach (var pt in _topicsByPublisher)
-            {
-                var publisherName = pt.Key;
-                var mqttClient = mqttClientFactory.CreateMqttClient();
-                var publisherOptions = new MqttClientOptionsBuilder()
-                    .WithTcpServer("localhost")
-                    .WithClientId(publisherName)
-                    .Build();
-                await mqttClient.ConnectAsync(publisherOptions);
-                _mqttPublisherClientsByPublisherName.Add(publisherName, mqttClient);
-            }
-            stopWatch.Stop();
+    public async Task Setup()
+    {
+        new TopicGenerator().Generate(NumPublishers, NumTopicsPerPublisher, out _topicsByPublisher, out _singleWildcardTopicsByPublisher, out _multiWildcardTopicsByPublisher);
 
-            Console.Write($"{NumPublishers} publisher(s) connected in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
-            Console.WriteLine($"connections per second: {NumPublishers / (stopWatch.ElapsedMilliseconds / 1000.0):0.000}");
+        var serverOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
+        var mqttClientFactory = new MqttClientFactory();
+        var mqttServerFactory = new MqttServerFactory();
+        _mqttServer = mqttServerFactory.CreateMqttServer(serverOptions);
+        await _mqttServer.StartAsync();
 
-            _mqttSubscriberClients = new List<IMqttClient>();
-            for (var i = 0; i < NumSubscribers; ++i)
-            {
-                var mqttClient = mqttClientFactory.CreateMqttClient();
-                var subsriberOptions = new MqttClientOptionsBuilder()
-                    .WithTcpServer("localhost")
-                    .WithClientId("sub" + i)
-                    .Build();
-                await mqttClient.ConnectAsync(subsriberOptions);
-                mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
-                _mqttSubscriberClients.Add(mqttClient);
-            }
+        Console.WriteLine();
+        Console.WriteLine("Begin connect " + NumPublishers + " publisher(s)...");
+
+        var stopWatch = new Stopwatch();
+        stopWatch.Start();
+        _mqttPublisherClientsByPublisherName = [];
+        foreach (var pt in _topicsByPublisher)
+        {
+            var publisherName = pt.Key;
+            var mqttClient = mqttClientFactory.CreateMqttClient();
+            var publisherOptions = new MqttClientOptionsBuilder()
+                .WithTcpServer("localhost")
+                .WithClientId(publisherName)
+                .Build();
+            await mqttClient.ConnectAsync(publisherOptions);
+            _mqttPublisherClientsByPublisherName.Add(publisherName, mqttClient);
+        }
+        stopWatch.Stop();
+
+        Console.Write($"{NumPublishers} publisher(s) connected in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
+        Console.WriteLine($"connections per second: {NumPublishers / (stopWatch.ElapsedMilliseconds / 1000.0):0.000}");
+
+        _mqttSubscriberClients = new List<IMqttClient>();
+        for (var i = 0; i < NumSubscribers; ++i)
+        {
+            var mqttClient = mqttClientFactory.CreateMqttClient();
+            var subsriberOptions = new MqttClientOptionsBuilder()
+                .WithTcpServer("localhost")
+                .WithClientId("sub" + i)
+                .Build();
+            await mqttClient.ConnectAsync(subsriberOptions);
+            mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
+            _mqttSubscriberClients.Add(mqttClient);
+        }
+    }
+
+    Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
+    {
+        // count messages and signal cancellation when expected message count is reached
+        ++_messagesReceivedCount;
+        if (_messagesReceivedCount == _messagesExpectedCount)
+        {
+            _cancellationTokenSource.Cancel();
+        }
+        return CompletedTask.Instance;
+    }
+
+    public async Task Cleanup()
+    {
+        foreach (var mqttClient in _mqttSubscriberClients)
+        {
+            await mqttClient.DisconnectAsync();
+            mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
+            mqttClient.Dispose();
         }
 
-        Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
+        foreach (var pub in _mqttPublisherClientsByPublisherName)
         {
-            // count messages and signal cancellation when expected message count is reached
-            ++_messagesReceivedCount;
-            if (_messagesReceivedCount == _messagesExpectedCount)
-            {
-                _cancellationTokenSource.Cancel();
-            }
-            return CompletedTask.Instance;
+            var mqttClient = pub.Value;
+            await mqttClient.DisconnectAsync();
+            mqttClient.Dispose();
         }
 
-        public async Task Cleanup()
+        await _mqttServer.StopAsync();
+        _mqttServer.Dispose();
+    }
+
+    /// <summary>
+    /// Measure no-wildcard topic subscription message exchange performance
+    /// </summary>
+    public Task Subscribe_to_No_Wildcard_Topics()
+    {
+        return ProcessMessages(_topicsByPublisher, "no wildcards");
+    }
+
+    /// <summary>
+    /// Measure single-wildcard topic subscription message exchange performance
+    /// </summary>
+    public Task Subscribe_to_Single_Wildcard_Topics()
+    {
+        return ProcessMessages(_singleWildcardTopicsByPublisher, "single wildcard");
+    }
+
+    /// <summary>
+    /// Measure multi-wildcard topic subscription message exchange performance
+    /// </summary>
+    public Task Subscribe_to_Multi_Wildcard_Topics()
+    {
+        return ProcessMessages(_multiWildcardTopicsByPublisher, "multi wildcard");
+    }
+
+
+    /// <summary>
+    ///  Subscribe to all topics, then run message exchange
+    /// </summary>
+    public async Task ProcessMessages(Dictionary<string, List<string>> topicsByPublisher, string topicTypeDescription)
+    {
+        var numTopics = CountTopics(topicsByPublisher);
+
+        Console.WriteLine();
+        Console.Write($"Subscribing to {numTopics} topics ");
+        ConsoleWriteInfo($"({topicTypeDescription})");
+        Console.WriteLine($" for {NumSubscribers} subscriber(s)...");
+
+        var stopWatch = new Stopwatch();
+        stopWatch.Start();
+
+        // each subscriber subscribes to all topics, one call per topic
+        foreach (var subscriber in _mqttSubscriberClients)
         {
-            foreach (var mqttClient in _mqttSubscriberClients)
-            {
-                await mqttClient.DisconnectAsync();
-                mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
-                mqttClient.Dispose();
-            }
-
-            foreach (var pub in _mqttPublisherClientsByPublisherName)
-            {
-                var mqttClient = pub.Value;
-                await mqttClient.DisconnectAsync();
-                mqttClient.Dispose();
-            }
-
-            await _mqttServer.StopAsync();
-            _mqttServer.Dispose();
-        }
-
-        /// <summary>
-        /// Measure no-wildcard topic subscription message exchange performance
-        /// </summary>
-        public Task Subscribe_to_No_Wildcard_Topics()
-        {
-            return ProcessMessages(_topicsByPublisher, "no wildcards");
-        }
-
-        /// <summary>
-        /// Measure single-wildcard topic subscription message exchange performance
-        /// </summary>
-        public Task Subscribe_to_Single_Wildcard_Topics()
-        {
-            return ProcessMessages(_singleWildcardTopicsByPublisher, "single wildcard");
-        }
-
-        /// <summary>
-        /// Measure multi-wildcard topic subscription message exchange performance
-        /// </summary>
-        public Task Subscribe_to_Multi_Wildcard_Topics()
-        {
-            return ProcessMessages(_multiWildcardTopicsByPublisher, "multi wildcard");
-        }
-
-
-        /// <summary>
-        ///  Subscribe to all topics, then run message exchange
-        /// </summary>
-        public async Task ProcessMessages(Dictionary<string, List<string>> topicsByPublisher, string topicTypeDescription)
-        {
-            var numTopics = CountTopics(topicsByPublisher);
-
-            Console.WriteLine();
-            Console.Write($"Subscribing to {numTopics} topics ");
-            ConsoleWriteInfo($"({topicTypeDescription})");
-            Console.WriteLine($" for {NumSubscribers} subscriber(s)...");
-
-            var stopWatch = new System.Diagnostics.Stopwatch();
-            stopWatch.Start();
-
-            // each subscriber subscribes to all topics, one call per topic
-            foreach (var subscriber in _mqttSubscriberClients)
-            {
-                foreach (var tp in topicsByPublisher)
-                {
-                    var topics = tp.Value;
-                    foreach (var topic in topics)
-                    {
-                        var topicFilter = new Packets.MqttTopicFilter() { Topic = topic };
-                        await subscriber.SubscribeAsync(topicFilter).ConfigureAwait(false);
-                    }
-                }
-            }
-
-            stopWatch.Stop();
-
-            Console.Write($"{NumSubscribers} subscriber(s) subscribed in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
-            Console.WriteLine($"subscribe calls per second: {numTopics / (stopWatch.ElapsedMilliseconds / 1000.0):0.000}");
-
-            await PublishAllAsync();
-
-            Console.WriteLine($"Unsubscribing {numTopics} topics ({topicTypeDescription}) for {NumSubscribers} subscriber(s)...");
-
-            stopWatch.Restart();
-
-            // unsubscribe to all topics, one call per topic
-            foreach (var subscriber in _mqttSubscriberClients)
-            {
-                foreach (var tp in topicsByPublisher)
-                {
-                    var topics = tp.Value;
-                    foreach (var topic in topics)
-                    {
-                        var topicFilter = new Packets.MqttTopicFilter() { Topic = topic };
-
-                        MqttClientUnsubscribeOptions options =
-                            new MqttClientUnsubscribeOptionsBuilder()
-                            .WithTopicFilter(topicFilter)
-                            .Build();
-                        await subscriber.UnsubscribeAsync(options).ConfigureAwait(false);
-                    }
-                }
-            }
-
-            stopWatch.Stop();
-
-            Console.Write($"{NumSubscribers} subscriber(s) unsubscribed in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
-            Console.WriteLine($"unsubscribe calls per second: {numTopics / (stopWatch.ElapsedMilliseconds / 1000.0):0.000}");
-        }
-
-        /// <summary>
-        /// Publish messages in batches of NumPublishCallsPerBatch, wait for messages sent to subscriber
-        /// </summary>
-        async Task PublishAllAsync()
-        {
-            Console.WriteLine("Begin message exchange...");
-
-            int publisherIndexCounter = 0;       // index to loop around all publishers to publish
-            int topicIndexCounter = 0;           // index to loop around all topics to publish
-            int totalNumMessagesReceived = 0;
-
-            var publisherNames = _topicsByPublisher.Keys.ToList();
-
-            // There should be one message received per publish
-            _messagesExpectedCount = NumPublishCallsPerBatch;
-
-            var stopWatch = new System.Diagnostics.Stopwatch();
-            stopWatch.Start();
-
-            // Loop for a while and exchange messages
-
-            while (stopWatch.ElapsedMilliseconds < 10000)
-            {
-                _messagesReceivedCount = 0;
-
-                _cancellationTokenSource = new CancellationTokenSource();
-
-                for (var publishCallCount = 0; publishCallCount < NumPublishCallsPerBatch; ++publishCallCount)
-                {
-                    // pick a publisher
-                    var publisherName = publisherNames[publisherIndexCounter % publisherNames.Count];
-                    var publisherTopics = _topicsByPublisher[publisherName];
-                    // pick a publisher topic
-                    var topic = publisherTopics[topicIndexCounter % publisherTopics.Count];
-                    var message = new MqttApplicationMessageBuilder()
-                        .WithTopic(topic)
-                        .Build();
-                    await _mqttPublisherClientsByPublisherName[publisherName].PublishAsync(message).ConfigureAwait(false);
-                    ++topicIndexCounter;
-                    ++publisherIndexCounter;
-                }
-
-                // Wait for at least one message per publish to be received by subscriber (in the subscriber's application message handler),
-                // then loop around to send another batch
-                try
-                {
-                    await Task.Delay(30000, _cancellationTokenSource.Token).ConfigureAwait(false);
-                }
-                catch
-                {
-                }
-
-                _cancellationTokenSource.Dispose();
-
-                if (_messagesReceivedCount < _messagesExpectedCount)
-                {
-                    ConsoleWriteLineError(string.Format("Messages Received Count mismatch, expected {0}, received {1}", _messagesExpectedCount, _messagesReceivedCount));
-                    return;
-                }
-
-                totalNumMessagesReceived += _messagesReceivedCount;
-            }
-
-            stopWatch.Stop();
-
-            Console.Write($"{totalNumMessagesReceived} messages published and received in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
-            ConsoleWriteLineSuccess($"messages per second: {(int)(totalNumMessagesReceived / (stopWatch.ElapsedMilliseconds / 1000.0))}");
-        }
-
-        int CountTopics(Dictionary<string, List<string>> topicsByPublisher)
-        {
-            var count = 0;
             foreach (var tp in topicsByPublisher)
             {
-                count += tp.Value.Count;
+                var topics = tp.Value;
+                foreach (var topic in topics)
+                {
+                    var topicFilter = new Packets.MqttTopicFilter() { Topic = topic };
+                    await subscriber.SubscribeAsync(topicFilter).ConfigureAwait(false);
+                }
             }
-            return count;
         }
 
-        void ConsoleWriteLineError(string message)
+        stopWatch.Stop();
+
+        Console.Write($"{NumSubscribers} subscriber(s) subscribed in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
+        Console.WriteLine($"subscribe calls per second: {numTopics / (stopWatch.ElapsedMilliseconds / 1000.0):0.000}");
+
+        await PublishAllAsync();
+
+        Console.WriteLine($"Unsubscribing {numTopics} topics ({topicTypeDescription}) for {NumSubscribers} subscriber(s)...");
+
+        stopWatch.Restart();
+
+        // unsubscribe to all topics, one call per topic
+        foreach (var subscriber in _mqttSubscriberClients)
         {
-            Console.ForegroundColor = ConsoleColor.Red;
-            Console.WriteLine(message);
-            Console.ResetColor();
+            foreach (var tp in topicsByPublisher)
+            {
+                var topics = tp.Value;
+                foreach (var topic in topics)
+                {
+                    var topicFilter = new Packets.MqttTopicFilter { Topic = topic };
+
+                    var options =
+                        new MqttClientUnsubscribeOptionsBuilder()
+                            .WithTopicFilter(topicFilter)
+                            .Build();
+                    await subscriber.UnsubscribeAsync(options).ConfigureAwait(false);
+                }
+            }
         }
 
-        void ConsoleWriteLineSuccess(string message)
-        {
-            Console.ForegroundColor = ConsoleColor.Green;
-            Console.WriteLine(message);
-            Console.ResetColor();
-        }
-
-        void ConsoleWriteInfo(string message)
-        {
-            Console.ForegroundColor = ConsoleColor.White;
-            Console.Write(message);
-            Console.ResetColor();
-        }
+        stopWatch.Stop();
 
+        Console.Write($"{NumSubscribers} subscriber(s) unsubscribed in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
+        Console.WriteLine($"unsubscribe calls per second: {numTopics / (stopWatch.ElapsedMilliseconds / 1000.0):0.000}");
     }
-}
+
+    /// <summary>
+    /// Publish messages in batches of NumPublishCallsPerBatch, wait for messages sent to subscriber
+    /// </summary>
+    async Task PublishAllAsync()
+    {
+        Console.WriteLine("Begin message exchange...");
+
+        var publisherIndexCounter = 0;       // index to loop around all publishers to publish
+        var topicIndexCounter = 0;           // index to loop around all topics to publish
+        var totalNumMessagesReceived = 0;
+
+        var publisherNames = _topicsByPublisher.Keys.ToList();
+
+        // There should be one message received per publish
+        _messagesExpectedCount = NumPublishCallsPerBatch;
+
+        var stopWatch = new Stopwatch();
+        stopWatch.Start();
+
+        // Loop for a while and exchange messages
+
+        while (stopWatch.ElapsedMilliseconds < 10000)
+        {
+            _messagesReceivedCount = 0;
+
+            _cancellationTokenSource = new CancellationTokenSource();
+
+            for (var publishCallCount = 0; publishCallCount < NumPublishCallsPerBatch; ++publishCallCount)
+            {
+                // pick a publisher
+                var publisherName = publisherNames[publisherIndexCounter % publisherNames.Count];
+                var publisherTopics = _topicsByPublisher[publisherName];
+                // pick a publisher topic
+                var topic = publisherTopics[topicIndexCounter % publisherTopics.Count];
+                var message = new MqttApplicationMessageBuilder()
+                    .WithTopic(topic)
+                    .Build();
+
+                await _mqttPublisherClientsByPublisherName[publisherName].PublishAsync(message).ConfigureAwait(false);
+                ++topicIndexCounter;
+                ++publisherIndexCounter;
+            }
+
+            // Wait for at least one message per publish to be received by subscriber (in the subscriber's application message handler),
+            // then loop around to send another batch
+            try
+            {
+                await Task.Delay(30000, _cancellationTokenSource.Token).ConfigureAwait(false);
+            }
+            catch (Exception exception)
+            {
+                Debug.Write(exception.ToString());
+            }
+
+            _cancellationTokenSource.Dispose();
+
+            if (_messagesReceivedCount < _messagesExpectedCount)
+            {
+                ConsoleWriteLineError($"Messages Received Count mismatch, expected {_messagesExpectedCount}, received {_messagesReceivedCount}");
+                return;
+            }
+
+            totalNumMessagesReceived += _messagesReceivedCount;
+        }
+
+        stopWatch.Stop();
+
+        Console.Write($"{totalNumMessagesReceived} messages published and received in {stopWatch.ElapsedMilliseconds / 1000.0:0.000} seconds, ");
+        ConsoleWriteLineSuccess($"messages per second: {(int)(totalNumMessagesReceived / (stopWatch.ElapsedMilliseconds / 1000.0))}");
+    }
+
+    static int CountTopics(Dictionary<string, List<string>> topicsByPublisher)
+    {
+        var count = 0;
+        foreach (var tp in topicsByPublisher)
+        {
+            count += tp.Value.Count;
+        }
+
+        return count;
+    }
+
+    static void ConsoleWriteLineError(string message)
+    {
+        Console.ForegroundColor = ConsoleColor.Red;
+        Console.WriteLine(message);
+        Console.ResetColor();
+    }
+
+    static void ConsoleWriteLineSuccess(string message)
+    {
+        Console.ForegroundColor = ConsoleColor.Green;
+        Console.WriteLine(message);
+        Console.ResetColor();
+    }
+
+    static void ConsoleWriteInfo(string message)
+    {
+        Console.ForegroundColor = ConsoleColor.White;
+        Console.Write(message);
+        Console.ResetColor();
+    }
+
+}

Source/MQTTnet.TestApp/MqttNetConsoleLogger.cs

@@ -6,58 +6,57 @@ using System;
 using System.Text;
 using MQTTnet.Diagnostics.Logger;
 
-namespace MQTTnet.TestApp
+namespace MQTTnet.TestApp;
+
+public static class MqttNetConsoleLogger
 {
-    public static class MqttNetConsoleLogger
+    static readonly object Lock = new();
+
+    public static void ForwardToConsole(MqttNetEventLogger logger)
     {
-        static readonly object _lock = new object();
+        ArgumentNullException.ThrowIfNull(logger);
 
-        public static void ForwardToConsole(MqttNetEventLogger logger)
+        logger.LogMessagePublished -= PrintToConsole;
+        logger.LogMessagePublished += PrintToConsole;
+    }
+
+    public static void PrintToConsole(string message, ConsoleColor color)
+    {
+        lock (Lock)
         {
-            ArgumentNullException.ThrowIfNull(logger);
-
-            logger.LogMessagePublished -= PrintToConsole;
-            logger.LogMessagePublished += PrintToConsole;
-        }
-
-        public static void PrintToConsole(string message, ConsoleColor color)
-        {
-            lock (_lock)
-            {
-                var backupColor = Console.ForegroundColor;
-                Console.ForegroundColor = color;
-                Console.Write(message);
-                Console.ForegroundColor = backupColor;
-            }
-        }
-
-        static void PrintToConsole(object sender, MqttNetLogMessagePublishedEventArgs e)
-        {
-            var output = new StringBuilder();
-            output.AppendLine($">> [{e.LogMessage.Timestamp:O}] [{e.LogMessage.ThreadId}] [{e.LogMessage.Source}] [{e.LogMessage.Level}]: {e.LogMessage.Message}");
-            if (e.LogMessage.Exception != null)
-            {
-                output.AppendLine(e.LogMessage.Exception.ToString());
-            }
-
-            var color = ConsoleColor.Red;
-            switch (e.LogMessage.Level)
-            {
-                case MqttNetLogLevel.Error:
-                    color = ConsoleColor.Red;
-                    break;
-                case MqttNetLogLevel.Warning:
-                    color = ConsoleColor.Yellow;
-                    break;
-                case MqttNetLogLevel.Info:
-                    color = ConsoleColor.Green;
-                    break;
-                case MqttNetLogLevel.Verbose:
-                    color = ConsoleColor.Gray;
-                    break;
-            }
-
-            PrintToConsole(output.ToString(), color);
+            var backupColor = Console.ForegroundColor;
+            Console.ForegroundColor = color;
+            Console.Write(message);
+            Console.ForegroundColor = backupColor;
         }
     }
+
+    static void PrintToConsole(object sender, MqttNetLogMessagePublishedEventArgs e)
+    {
+        var output = new StringBuilder();
+        output.AppendLine($">> [{e.LogMessage.Timestamp:O}] [{e.LogMessage.ThreadId}] [{e.LogMessage.Source}] [{e.LogMessage.Level}]: {e.LogMessage.Message}");
+        if (e.LogMessage.Exception != null)
+        {
+            output.AppendLine(e.LogMessage.Exception.ToString());
+        }
+
+        var color = ConsoleColor.Red;
+        switch (e.LogMessage.Level)
+        {
+            case MqttNetLogLevel.Error:
+                color = ConsoleColor.Red;
+                break;
+            case MqttNetLogLevel.Warning:
+                color = ConsoleColor.Yellow;
+                break;
+            case MqttNetLogLevel.Info:
+                color = ConsoleColor.Green;
+                break;
+            case MqttNetLogLevel.Verbose:
+                color = ConsoleColor.Gray;
+                break;
+        }
+
+        PrintToConsole(output.ToString(), color);
+    }
 }