1612 mqttserver subscription to similar base and subtopic with wildcards fails (#1622)

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 13.0.1 to 13.0.2.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](https://github.com/JamesNK/Newtonsoft.Json/compare/13.0.1...13.0.2)

---
updated-dependencies:
- dependency-name: Newtonsoft.Json
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ReleaseNotes.md

@@ -1 +1,9 @@
-
+* [Core] Fixed a memory leak in _AsyncSignal_ implementation (#1586, thanks to @mario-zelger).
+* [Core] Fixed an issue with bounds handling in _MqttBufferReader_ (#1593).
+* [Core] Performance improvements and reduced memory usage due to improved buffer copies (#1599, thanks to @xljiulang).
+* [Server] Fix not properly reset statistics (#1587, thanks to @damikun).
+* [Server] Now using an empty string as the sender client ID for injected application messages (#1583, thanks to @xljiulang).
+* [Server] Improved memory usage for ASP.NET connections (#1582, thanks to @xljiulang).
+* [Server] Improved memory usage and performance for ASP.NET integration (#1596, thanks to @xljiulang).
+* [Server] Add support for interception of will messages (#1613).
+* [Server] Fixed wrong topic filter detections (#1615, thanks to @logicaloud).

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ name: CI
 on: [push, pull_request]
 
 env:
-  VERSION: "4.1.3.${{github.run_number}}"
+  VERSION: "4.1.4.${{github.run_number}}"
 
 jobs:
   build:
@@ -60,8 +60,4 @@ jobs:
 
       - name: Publish MyGet nugets
         if: ${{ github.event_name == 'push' }}
-        run: dotnet nuget push **/*.nupkg -k ${{ secrets.MYGET_API_KEY }} -s https://www.myget.org/F/mqttnet/api/v3/index.json --skip-duplicate
-
-#      - name: Publish nugets
-#        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
-#        run: dotnet nuget push **/*.nupkg -k ${{ secrets.NUGET_API_KEY }} -s https://api.nuget.org/v3/index.json --skip-duplicate
+        run: dotnet nuget push **/*.nupkg -k ${{ secrets.MYGET_API_KEY }} -s https://www.myget.org/F/mqttnet/api/v3/index.json --skip-duplicate

MQTTnet.sln.DotSettings

@@ -240,8 +240,14 @@ See the LICENSE file in the project root for more information.</s:String>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002ECSharpPlaceAttributeOnSameLineMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateBlankLinesAroundFieldToBlankLinesAroundProperty/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateThisQualifierSettings/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=CONNACK/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=PINGREQ/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=PINGRESP/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=PUBACK/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=PUBCOMP/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=PUBREC/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=PUBREL/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=SUBACK/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Tnet/@EntryIndexedValue">True</s:Boolean>
-	<s:Boolean x:Key="/Default/UserDictionary/Words/=unsub/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=unsub/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=UNSUBACK/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

README.md

@@ -4,7 +4,7 @@
 </p>
 
 [![NuGet Badge](https://buildstats.info/nuget/MQTTnet)](https://www.nuget.org/packages/MQTTnet)
-[![CI](https://github.com/dotnet/MQTTnet/actions/workflows/ci.yml/badge.svg)](https://github.com/dotnet/MQTTnet/actions/workflows/ci.yml)
+[![CI](https://github.com/dotnet/MQTTnet/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/dotnet/MQTTnet/actions/workflows/ci.yml)
 [![MyGet](https://img.shields.io/myget/mqttnet/v/mqttnet?color=orange&label=MyGet-Preview)](https://www.myget.org/feed/mqttnet/package/nuget/MQTTnet)
 ![Size](https://img.shields.io/github/repo-size/dotnet/MQTTnet.svg)
 [![Join the chat at https://gitter.im/MQTTnet/community](https://badges.gitter.im/MQTTnet/community.svg)](https://gitter.im/MQTTnet/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)

Samples/Client/Client_Connection_Samples.cs

@@ -138,7 +138,7 @@ public static class Client_Connection_Samples
     {
         /*
          * This sample creates a simple MQTT client and connects to a public broker using a WebSocket connection.
-         * Instead of the .NET implementation of WebSockets the implementaion from WebSocket4Net is used. It provides more
+         * Instead of the .NET implementation of WebSockets the implementation from WebSocket4Net is used. It provides more
          * encryption algorithms and supports more platforms.
          * 
          * This is a modified version of the sample _Connect_Client_! See other sample for more details.
@@ -386,4 +386,4 @@ public static class Client_Connection_Samples
                 });
         }
     }
-}
+}

Samples/MQTTnet.Samples.csproj

@@ -9,12 +9,10 @@
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <EnableNETAnalyzers>false</EnableNETAnalyzers>
         <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <NoWarn>1591</NoWarn>
+        <NoWarn>1591;NETSDK1138</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.CodeAnalysis.Compilers" Version="4.0.1" />
-        <PackageReference Include="Microsoft.Net.Compilers" Version="4.0.1" />
 
         <ProjectReference Include="..\Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj" />
         <ProjectReference Include="..\Source\MQTTnet.Extensions.ManagedClient\MQTTnet.Extensions.ManagedClient.csproj" />

Source/MQTTnet.AspNetCore.Tests/MQTTnet.AspNetCore.Tests.csproj

@@ -12,8 +12,6 @@
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.2.0" />
         <PackageReference Include="MSTest.TestAdapter" Version="2.2.10" />
         <PackageReference Include="MSTest.TestFramework" Version="2.2.10" />
-        <PackageReference Include="Microsoft.CodeAnalysis.Compilers" Version="4.0.1" />
-        <PackageReference Include="Microsoft.Net.Compilers" Version="4.0.1" />
     </ItemGroup>
 
     <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">

Source/MQTTnet.AspNetCore.Tests/MqttConnectionContextTest.cs

@@ -18,7 +18,7 @@ using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
-using MQTTnet.Tests.Extensions;
+using MQTTnet.Tests.Helpers;
 
 namespace MQTTnet.AspNetCore.Tests
 {
@@ -35,7 +35,7 @@ namespace MQTTnet.AspNetCore.Tests
             connection.Transport = pipe;
             var ctx = new MqttConnectionContext(serializer, connection);
 
-            await pipe.Receive.Writer.WriteAsync(writer.AddMqttHeader(MqttControlPacketType.Connect, new byte[0]));
+            await pipe.Receive.Writer.WriteAsync(writer.AddMqttHeader(MqttControlPacketType.Connect, Array.Empty<byte>()));
 
             await Assert.ThrowsExceptionAsync<MqttProtocolViolationException>(() => ctx.ReceivePacketAsync(CancellationToken.None));
 

Source/MQTTnet.AspTestApp/MQTTnet.AspTestApp.csproj

@@ -8,17 +8,15 @@
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <EnableNETAnalyzers>false</EnableNETAnalyzers>
         <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
+        <NoWarn>1591;NETSDK1138</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
-        <ProjectReference Include="..\..\Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj"/>
-
-        <PackageReference Include="Microsoft.CodeAnalysis.Compilers" Version="4.0.1" />
-        <PackageReference Include="Microsoft.Net.Compilers" Version="4.0.1" />
+        <ProjectReference Include="..\..\Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj" />
     </ItemGroup>
 
     <ItemGroup>
-        <Folder Include="wwwroot\"/>
+        <Folder Include="wwwroot\" />
     </ItemGroup>
 
 </Project>

Source/MQTTnet.AspnetCore/MQTTnet.AspNetCore.csproj

@@ -32,7 +32,8 @@
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
-        <NoWarn>1591</NoWarn>
+        <NoWarn>1591;NETSDK1138</NoWarn>
+        <LangVersion>7.3</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>

Source/MQTTnet.AspnetCore/MqttConnectionContext.cs

@@ -2,38 +2,59 @@
 // 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.IO.Pipelines;
+using System.Net;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Http.Connections.Features;
+using Microsoft.AspNetCore.Http.Features;
 using MQTTnet.Adapter;
 using MQTTnet.AspNetCore.Client.Tcp;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
-using MQTTnet.Packets;
-using System;
-using System.IO.Pipelines;
-using System.Security.Cryptography.X509Certificates;
-using System.Threading;
-using System.Threading.Tasks;
 using MQTTnet.Internal;
+using MQTTnet.Packets;
 
 namespace MQTTnet.AspNetCore
 {
     public sealed class MqttConnectionContext : IMqttChannelAdapter
     {
+        readonly ConnectionContext _connection;
         readonly AsyncLock _writerLock = new AsyncLock();
-        
+
         PipeReader _input;
         PipeWriter _output;
-        
+
         public MqttConnectionContext(MqttPacketFormatterAdapter packetFormatterAdapter, ConnectionContext connection)
         {
             PacketFormatterAdapter = packetFormatterAdapter ?? throw new ArgumentNullException(nameof(packetFormatterAdapter));
-            Connection = connection ?? throw new ArgumentNullException(nameof(connection));
+            _connection = connection ?? throw new ArgumentNullException(nameof(connection));
 
-            if (Connection.Transport != null)
+            _input = connection.Transport.Input;
+            _output = connection.Transport.Output;
+        }
+
+        public long BytesReceived { get; private set; }
+
+        public long BytesSent { get; private set; }
+
+        public X509Certificate2 ClientCertificate
+        {
+            get
             {
-                _input = Connection.Transport.Input;
-                _output = Connection.Transport.Output;
+                // mqtt over tcp
+                var tlsFeature = _connection.Features.Get<ITlsConnectionFeature>();
+                if (tlsFeature != null)
+                {
+                    return tlsFeature.ClientCertificate;
+                }
+
+                // mqtt over websocket
+                var httpFeature = _connection.Features.Get<IHttpContextFeature>();
+                return httpFeature?.HttpContext?.Connection.ClientCertificate;
             }
         }
 
@@ -41,47 +62,59 @@ namespace MQTTnet.AspNetCore
         {
             get
             {
-#if NETCOREAPP3_1
-                if (Connection?.RemoteEndPoint != null)
+                // mqtt over tcp 
+#if NETCOREAPP3_1_OR_GREATER
+                if (_connection.RemoteEndPoint != null)
                 {
-                    return Connection.RemoteEndPoint.ToString();
+                    return _connection.RemoteEndPoint.ToString();
                 }
 #endif
-                var connection = Http?.HttpContext?.Connection;
-                if (connection == null)
+                // mqtt over websocket
+                var httpFeature = _connection.Features.Get<IHttpConnectionFeature>();
+                if (httpFeature?.RemoteIpAddress != null)
                 {
-                    return Connection.ConnectionId;
+                    return new IPEndPoint(httpFeature.RemoteIpAddress, httpFeature.RemotePort).ToString();
                 }
 
-                return $"{connection.RemoteIpAddress}:{connection.RemotePort}";
+                return null;
             }
         }
 
-        public bool IsSecureConnection => Http?.HttpContext?.Request?.IsHttps ?? false;
-
-        public X509Certificate2 ClientCertificate => Http?.HttpContext?.Connection?.ClientCertificate;
-
-        public ConnectionContext Connection { get; }
-        
-        public MqttPacketFormatterAdapter PacketFormatterAdapter { get; }
-
-        public long BytesSent { get; set; }
-
-        public long BytesReceived { get; set; }
-
         public bool IsReadingPacket { get; private set; }
 
-        IHttpContextFeature Http => Connection.Features.Get<IHttpContextFeature>();
+        public bool IsSecureConnection
+        {
+            get
+            {
+                // mqtt over tcp
+                var tlsFeature = _connection.Features.Get<ITlsConnectionFeature>();
+                if (tlsFeature != null)
+                {
+                    return true;
+                }
+
+                // mqtt over websocket
+                var httpFeature = _connection.Features.Get<IHttpContextFeature>();
+                if (httpFeature?.HttpContext != null)
+                {
+                    return httpFeature.HttpContext.Request.IsHttps;
+                }
+
+                return false;
+            }
+        }
+
+        public MqttPacketFormatterAdapter PacketFormatterAdapter { get; }
 
         public async Task ConnectAsync(CancellationToken cancellationToken)
         {
-            if (Connection is TcpConnection tcp && !tcp.IsConnected)
+            if (_connection is TcpConnection tcp && !tcp.IsConnected)
             {
                 await tcp.StartAsync().ConfigureAwait(false);
             }
 
-            _input = Connection.Transport.Input;
-            _output = Connection.Transport.Output;
+            _input = _connection.Transport.Input;
+            _output = _connection.Transport.Output;
         }
 
         public Task DisconnectAsync(CancellationToken cancellationToken)
@@ -92,16 +125,19 @@ namespace MQTTnet.AspNetCore
             return Task.CompletedTask;
         }
 
+        public void Dispose()
+        {
+            _writerLock.Dispose();
+        }
+
         public async Task<MqttPacket> ReceivePacketAsync(CancellationToken cancellationToken)
         {
-            var input = Connection.Transport.Input;
-
             try
             {
                 while (!cancellationToken.IsCancellationRequested)
                 {
                     ReadResult readResult;
-                    var readTask = input.ReadAsync(cancellationToken);
+                    var readTask = _input.ReadAsync(cancellationToken);
                     if (readTask.IsCompleted)
                     {
                         readResult = readTask.Result;
@@ -141,15 +177,15 @@ namespace MQTTnet.AspNetCore
                         // 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);
+                        _input.AdvanceTo(consumed, observed);
                     }
                 }
             }
-            catch (Exception e)
+            catch (Exception exception)
             {
                 // completing the channel makes sure that there is no more data read after a protocol error
-                _input?.Complete(e);
-                _output?.Complete(e);
+                _input?.Complete(exception);
+                _output?.Complete(exception);
                 throw;
             }
             finally
@@ -169,25 +205,35 @@ namespace MQTTnet.AspNetCore
 
         public async Task SendPacketAsync(MqttPacket packet, CancellationToken cancellationToken)
         {
-            var formatter = PacketFormatterAdapter;
-            
             using (await _writerLock.EnterAsync(cancellationToken).ConfigureAwait(false))
             {
-                var buffer = formatter.Encode(packet);
-                var msg = buffer.Join().AsMemory();
-                var output = _output;
-                var result = await output.WriteAsync(msg, cancellationToken).ConfigureAwait(false);
-                if (result.IsCompleted)
+                try
                 {
-                    BytesSent += msg.Length;
-                }
+                    var buffer = PacketFormatterAdapter.Encode(packet);
 
-                PacketFormatterAdapter.Cleanup();
+                    WritePacketBuffer(_output, buffer);
+                    await _output.FlushAsync(cancellationToken).ConfigureAwait(false);
+
+                    BytesSent += buffer.Length;
+                }
+                finally
+                {
+                    PacketFormatterAdapter.Cleanup();
+                }
             }
         }
 
-        public void Dispose()
+        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.AsSpan().CopyTo(span.Slice(buffer.Packet.Count));
+
+            output.Advance(buffer.Length);
         }
     }
-}
+}

Source/MQTTnet.AspnetCore/ReaderExtensions.cs

@@ -2,21 +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;
-using System.Buffers;
 using MQTTnet.Adapter;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
+using System;
+using System.Buffers;
+using System.Linq;
+using System.Runtime.InteropServices;
 
 namespace MQTTnet.AspNetCore
 {
     public static class ReaderExtensions
     {
-        public static bool TryDecode(this MqttPacketFormatterAdapter formatter, 
-            in ReadOnlySequence<byte> input, 
-            out MqttPacket packet, 
-            out SequencePosition consumed, 
+        public static bool TryDecode(this MqttPacketFormatterAdapter formatter,
+            in ReadOnlySequence<byte> input,
+            out MqttPacket packet,
+            out SequencePosition consumed,
             out SequencePosition observed,
             out int bytesRead)
         {
@@ -33,22 +35,22 @@ namespace MQTTnet.AspNetCore
                 return false;
             }
 
-            var fixedHeader = copy.First.Span[0];
-            if (!TryReadBodyLength(ref copy, out int headerLength, out var bodyLength))
+            if (!TryReadBodyLength(ref copy, out var headerLength, out var bodyLength))
             {
                 return false;
             }
 
+            var fixedHeader = copy.First.Span[0];
+            copy = copy.Slice(headerLength);
             if (copy.Length < bodyLength)
             {
                 return false;
             }
 
             var bodySlice = copy.Slice(0, bodyLength);
-            var buffer = bodySlice.GetMemory().ToArray();
-            
-            var receivedMqttPacket = new ReceivedMqttPacket(fixedHeader, new ArraySegment<byte>(buffer, 0, buffer.Length), buffer.Length + 2);
-
+            var bodySegment = GetArraySegment(ref bodySlice); 
+    
+            var receivedMqttPacket = new ReceivedMqttPacket(fixedHeader, bodySegment, headerLength + bodyLength);
             if (formatter.ProtocolVersion == MqttProtocolVersion.Unknown)
             {
                 formatter.DetectProtocolVersion(receivedMqttPacket);
@@ -61,18 +63,41 @@ namespace MQTTnet.AspNetCore
             return true;
         }
 
-        static ReadOnlyMemory<byte> GetMemory(this in ReadOnlySequence<byte> input)
+        static ArraySegment<byte> GetArraySegment(ref ReadOnlySequence<byte> input)
         {
-            if (input.IsSingleSegment)
+            if (input.IsSingleSegment && MemoryMarshal.TryGetArray(input.First, out var segment))
             {
-                return input.First;
+                return segment;
             }
 
             // Should be rare
-            return input.ToArray();
+            var array = input.ToArray();
+            return new ArraySegment<byte>(array);
         }
 
         static bool TryReadBodyLength(ref ReadOnlySequence<byte> input, out int headerLength, out int bodyLength)
+        {
+            var valueSequence = input.Slice(0, Math.Min(5, input.Length));
+            if (valueSequence.IsSingleSegment)
+            {
+                var valueSpan =
+#if NET5_0_OR_GREATER
+                    valueSequence.FirstSpan;
+#else
+                    valueSequence.First.Span;
+#endif
+                return TryReadBodyLength(valueSpan, out headerLength, out bodyLength);
+            }
+            else
+            {
+                Span<byte> valueSpan = stackalloc byte[8];
+                valueSequence.CopyTo(valueSpan);
+                valueSpan = valueSpan.Slice(0, (int)valueSequence.Length);
+                return TryReadBodyLength(valueSpan, out headerLength, out bodyLength);
+            }
+        }
+
+        static bool TryReadBodyLength(ReadOnlySpan<byte> span, 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;
@@ -81,33 +106,35 @@ namespace MQTTnet.AspNetCore
             var index = 1;
             headerLength = 0;
             bodyLength = 0;
-            
-            var temp = input.Slice(0, Math.Min(5, input.Length)).GetMemory().Span;
 
             do
             {
-                if (index == temp.Length)
+                if (index == span.Length)
                 {
                     return false;
                 }
 
-                encodedByte = temp[index];
+                encodedByte = span[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())}).");
+                    ThrowProtocolViolationException(span, index);
                 }
 
                 multiplier *= 128;
             } while ((encodedByte & 128) != 0);
 
-            input = input.Slice(index);
-
             headerLength = index;
             bodyLength = value;
             return true;
         }
+
+
+        static void ThrowProtocolViolationException(ReadOnlySpan<byte> valueSpan, int index)
+        {
+            throw new MqttProtocolViolationException($"Remaining length is invalid (Data={string.Join(",", valueSpan.Slice(1, index).ToArray())}).");
+        }
     }
 }

Source/MQTTnet.Benchmarks/BaseBenchmark.cs

@@ -1,3 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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
 {
     public abstract class BaseBenchmark

Source/MQTTnet.Benchmarks/ChannelAdapterBenchmark.cs

@@ -2,54 +2,25 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using BenchmarkDotNet.Attributes;
-using MQTTnet.Adapter;
-using MQTTnet.Internal;
-using MQTTnet.Packets;
 using System;
 using System.IO;
 using System.Threading;
+using BenchmarkDotNet.Attributes;
+using MQTTnet.Adapter;
 using MQTTnet.Diagnostics;
 using MQTTnet.Formatter;
+using MQTTnet.Packets;
 using MQTTnet.Tests.Mockups;
 
 namespace MQTTnet.Benchmarks
 {
     [MemoryDiagnoser]
-    public sealed class ChannelAdapterBenchmark
+    public sealed class ChannelAdapterBenchmark : BaseBenchmark
     {
         MqttChannelAdapter _channelAdapter;
         int _iterations;
-        MemoryStream _stream;
         MqttPublishPacket _packet;
-
-        [GlobalSetup]
-        public void Setup()
-        {
-            _packet = new MqttPublishPacket
-            {
-                Topic = "A"
-            };
-
-            var serializer = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
-            
-            var serializedPacket = Join(serializer.Encode(_packet).Join());
-
-            _iterations = 10000;
-
-            _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, null, new MqttNetEventLogger());
-        }
+        MemoryStream _stream;
 
         [Benchmark]
         public void Receive_10000_Messages()
@@ -77,6 +48,34 @@ namespace MQTTnet.Benchmarks
             _stream.Position = 0;
         }
 
+        [GlobalSetup]
+        public void Setup()
+        {
+            _packet = new MqttPublishPacket
+            {
+                Topic = "A"
+            };
+
+            var serializer = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
+
+            var serializedPacket = Join(serializer.Encode(_packet).Join());
+
+            _iterations = 10000;
+
+            _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, null, new MqttNetEventLogger());
+        }
+
         static byte[] Join(params ArraySegment<byte>[] chunks)
         {
             var buffer = new MemoryStream();
@@ -88,4 +87,4 @@ namespace MQTTnet.Benchmarks
             return buffer.ToArray();
         }
     }
-}
+}

Source/MQTTnet.Benchmarks/Configurations/AllowNonOptimized.cs

@@ -1,22 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using BenchmarkDotNet.Jobs;
-using BenchmarkDotNet.Validators;
-
-namespace MQTTnet.Benchmarks.Configurations
-{
-    /// <summary>
-    /// this options may be used to run benchmarks in debugmode and attach a performance profiler
-    /// https://benchmarkdotnet.org/Configs/Configs.htm
-    /// </summary>
-    public class AllowNonOptimized : BaseConfig
-    {
-        public AllowNonOptimized()
-        {
-            AddValidator(JitOptimizationsValidator.DontFailOnError); // ALLOW NON-OPTIMIZED DLLS
-            AddJob(Job.InProcess);
-        }
-    }
-}

Source/MQTTnet.Benchmarks/Configurations/BaseConfig.cs

@@ -1,19 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using BenchmarkDotNet.Configs;
-using System.Linq;
-
-namespace MQTTnet.Benchmarks.Configurations
-{
-    public class BaseConfig : ManualConfig
-    {
-        public BaseConfig()
-        {
-            AddLogger(DefaultConfig.Instance.GetLoggers().ToArray()); // manual config has no loggers by default
-            AddExporter(DefaultConfig.Instance.GetExporters().ToArray()); // manual config has no exporters by default
-            AddColumnProvider(DefaultConfig.Instance.GetColumnProviders().ToArray()); // manual config has no columns by default
-        }
-    }
-}

Source/MQTTnet.Benchmarks/Configurations/RuntimeCompareConfig.cs

@@ -1,19 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using BenchmarkDotNet.Environments;
-using BenchmarkDotNet.Jobs;
-using BenchmarkDotNet.Toolchains.CsProj;
-
-namespace MQTTnet.Benchmarks.Configurations
-{
-    public class RuntimeCompareConfig : BaseConfig
-    {
-        public RuntimeCompareConfig()
-        {
-            AddJob(Job.Default.WithRuntime(ClrRuntime.Net48));
-            AddJob(Job.Default.WithRuntime(CoreRuntime.Core50).WithToolchain(CsProjCoreToolchain.NetCoreApp50));
-        }
-    }
-}

Source/MQTTnet.Benchmarks/LoggerBenchmark.cs

@@ -11,7 +11,7 @@ namespace MQTTnet.Benchmarks
     [SimpleJob(RuntimeMoniker.Net60)]
     [RPlotExporter]
     [MemoryDiagnoser]
-    public class LoggerBenchmark
+    public class LoggerBenchmark : BaseBenchmark
     {
         MqttNetNullLogger _nullLogger;
         MqttNetSourceLogger _sourceNullLogger;

Source/MQTTnet.Benchmarks/MQTTnet.Benchmarks.csproj

@@ -1,14 +1,16 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
+        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
         <OutputType>Exe</OutputType>
         <DebugType>Full</DebugType>
-        <TargetFrameworks>net5.0;net6.0</TargetFrameworks>
+        <TargetFrameworks>net6.0</TargetFrameworks>
         <LangVersion>7.2</LangVersion>
         <IsPackable>false</IsPackable>
         <EnableNETAnalyzers>false</EnableNETAnalyzers>
         <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
+        <NoWarn>1591;NETSDK1138</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
@@ -26,9 +28,6 @@
 
     <ItemGroup>
         <ProjectReference Include="..\..\Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj" />
-
-        <PackageReference Include="Microsoft.CodeAnalysis.Compilers" Version="4.0.1" />
-        <PackageReference Include="Microsoft.Net.Compilers" Version="4.0.1" />
         <ProjectReference Include="..\MQTTnet.Tests\MQTTnet.Tests.csproj" />
     </ItemGroup>
 

Source/MQTTnet.Benchmarks/MemoryCopyBenchmark.cs

@@ -0,0 +1,40 @@
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Jobs;
+using System;
+
+
+namespace MQTTnet.Benchmarks
+{
+    [SimpleJob(RuntimeMoniker.Net60)]
+    [RPlotExporter, RankColumn]
+    [MemoryDiagnoser]
+    public class MemoryCopyBenchmark
+    {
+        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/MQTTnet.Benchmarks/MessageDeliveryBenchmark.cs

@@ -1,5 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
 using BenchmarkDotNet.Attributes;
-using BenchmarkDotNet.Jobs;
 using MQTTnet.Client;
 using MQTTnet.Server;
 using System;
@@ -8,14 +11,10 @@ using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 
-
 namespace MQTTnet.Benchmarks
 {
-    /// <summary>
-    /// Create a number of topics, publish, subscribe, and wait for response
-    /// </summary>
     [MemoryDiagnoser]
-    public class MessageDeliveryBenchmark
+    public class MessageDeliveryBenchmark : BaseBenchmark
     {
         List<MqttApplicationMessage> _topicPublishMessages;
 

Source/MQTTnet.Benchmarks/MessageProcessingBenchmark.cs

@@ -12,7 +12,7 @@ namespace MQTTnet.Benchmarks
     [SimpleJob(RuntimeMoniker.Net60)]
     [RPlotExporter, RankColumn]
     [MemoryDiagnoser]
-    public class MessageProcessingBenchmark
+    public class MessageProcessingBenchmark : BaseBenchmark
     {
         MqttServer _mqttServer;
         IMqttClient _mqttClient;

Source/MQTTnet.Benchmarks/MessageProcessingMqttConnectionContextBenchmark.cs

@@ -15,7 +15,7 @@ namespace MQTTnet.Benchmarks
 {
     [SimpleJob(RuntimeMoniker.Net60)]
     [MemoryDiagnoser]
-    public class MessageProcessingMqttConnectionContextBenchmark
+    public class MessageProcessingMqttConnectionContextBenchmark : BaseBenchmark
     {
         IWebHost _host;
         IMqttClient _mqttClient;

Source/MQTTnet.Benchmarks/MqttBufferReaderBenchmark.cs

@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Text;
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Jobs;
+using MQTTnet.Formatter;
+
+namespace MQTTnet.Benchmarks
+{
+    [SimpleJob(RuntimeMoniker.Net60)]
+    [MemoryDiagnoser]
+    public class MqttBufferReaderBenchmark
+    {
+        byte[] _buffer;
+        int _bufferLength;
+
+        [GlobalSetup]
+        public void GlobalSetup()
+        {
+            var writer = new MqttBufferWriter(1024, 1024);
+            writer.WriteString("hgfjkdfkjlghfdjghdfljkdfhgdlkjfshgsldkfjghsdflkjghdsflkjhrstiuoghlkfjbhnfbutghjoiöjhklötnbhtroliöuhbjntluiobkjzbhtdrlskbhtruhjkfthgbkftgjhgfiklhotriuöhbjtrsioöbtrsötrhträhtrühjtriüoätrhjtsrölbktrbnhtrulöbionhströloubinströoliubhnsöotrunbtöroisntröointröioujhgötiohjgötorshjnbgtöorihbnjtröoihbjntröobntröoibntrjhötrohjbtröoihntröoibnrtoiöbtrjnboöitrhjtnriohötrhjtöroihjtroöihjtroösibntsroönbotöirsbntöoihjntröoihntroöbtrboöitrnhoöitrhjntröoishbnjtröosbhtröbntriohjtröoijtöoitbjöotibjnhöotirhbjntroöibhnjrtoöibnhtroöibnhtörsbnhtöoirbnhtöroibntoörhjnbträöbtrbträbtrbtirbätrsibohjntrsöiobthnjiohjsrtoib");
+
+            _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_Encoding()
+        {
+            Encoding.UTF8.GetString(_buffer, 0, _bufferLength);
+        }
+    }
+}

Source/MQTTnet.Benchmarks/MqttPacketReaderWriterBenchmark.cs

@@ -1,7 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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;
-using MQTTnet.AspNetCore;
 using MQTTnet.Formatter;
 using MQTTnet.Tests.Mockups;
 
@@ -9,7 +12,7 @@ namespace MQTTnet.Benchmarks
 {
     [SimpleJob(RuntimeMoniker.Net60)]
     [MemoryDiagnoser]
-    public class MqttPacketReaderWriterBenchmark
+    public class MqttPacketReaderWriterBenchmark : BaseBenchmark
     {
         readonly byte[] _demoPayload = new byte[1024];
         

Source/MQTTnet.Benchmarks/MqttTcpChannelBenchmark.cs

@@ -17,7 +17,7 @@ namespace MQTTnet.Benchmarks
 {
     [SimpleJob(RuntimeMoniker.Net60)]
     [MemoryDiagnoser]
-    public sealed class MqttTcpChannelBenchmark
+    public class MqttTcpChannelBenchmark : BaseBenchmark
     {
         MqttServer _mqttServer;
         IMqttChannel _serverChannel;

Source/MQTTnet.Benchmarks/Program.cs

@@ -3,85 +3,140 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
+using BenchmarkDotNet.Loggers;
 using BenchmarkDotNet.Running;
-using MQTTnet.Benchmarks.Configurations;
 using MQTTnet.Diagnostics;
 
 namespace MQTTnet.Benchmarks
 {
     public static class Program
     {
-        public static void Main(string[] args)
-        {
-            Console.WriteLine($"MQTTnet - Benchmarks ({TargetFrameworkProvider.TargetFramework})");
-            Console.WriteLine("--------------------------------------------------------");
-            Console.WriteLine("1 = MessageProcessingBenchmark");
-            Console.WriteLine("2 = SerializerBenchmark");
-            Console.WriteLine("3 = LoggerBenchmark");
-            Console.WriteLine("4 = TopicFilterComparerBenchmark");
-            Console.WriteLine("5 = ChannelAdapterBenchmark");
-            Console.WriteLine("6 = MqttTcpChannelBenchmark");
-            Console.WriteLine("7 = TcpPipesBenchmark");
-            Console.WriteLine("8 = MessageProcessingMqttConnectionContextBenchmark");
-            Console.WriteLine("9 = ServerProcessingBenchmark");
-            Console.WriteLine("a = MqttPacketReaderWriterBenchmark");
-            Console.WriteLine("b = RoundtripBenchmark");
-            Console.WriteLine("c = SubscribeBenchmark");
-            Console.WriteLine("d = UnsubscribeBenchmark");
-            Console.WriteLine("e = MessageDeliveryBenchmark");
-            Console.WriteLine("f = AsyncLockBenchmark");
+        static int _selectedBenchmarkIndex;
+        static List<Type> _benchmarks;
 
-            var pressedKey = Console.ReadKey(true);
-            switch (pressedKey.KeyChar)
+        public static void Main(string[] arguments)
+        {
+            _benchmarks = CollectBenchmarks();
+            HandleArguments(arguments);
+
+            while (true)
             {
-                case '1':
-                    BenchmarkRunner.Run<MessageProcessingBenchmark>();
-                    break;
-                case '2':
-                    BenchmarkRunner.Run<SerializerBenchmark>();
-                    break;
-                case '3':
-                    BenchmarkRunner.Run<LoggerBenchmark>();
-                    break;
-                case '4':
-                    BenchmarkRunner.Run<TopicFilterComparerBenchmark>();
-                    break;
-                case '5':
-                    BenchmarkRunner.Run<ChannelAdapterBenchmark>();
-                    break;
-                case '6':
-                    BenchmarkRunner.Run<MqttTcpChannelBenchmark>();
-                    break;
-                case '7':
-                    BenchmarkRunner.Run<TcpPipesBenchmark>();
-                    break;
-                case '8':
-                    BenchmarkRunner.Run<MessageProcessingMqttConnectionContextBenchmark>(new RuntimeCompareConfig());
-                    break;
-                case '9':
-                    BenchmarkRunner.Run<ServerProcessingBenchmark>();
-                    break;
-                case 'a':
-                    BenchmarkRunner.Run(typeof(MqttPacketReaderWriterBenchmark));
-                    break;
-                case 'b':
-                    BenchmarkRunner.Run<RoundtripProcessingBenchmark>();
-                    break;
-                case 'c':
-                    BenchmarkRunner.Run<SubscribeBenchmark>();
-                    break;
-                case 'd':
-                    BenchmarkRunner.Run<UnsubscribeBenchmark>();
-                    break;
-                case 'e':
-                    BenchmarkRunner.Run<MessageDeliveryBenchmark>();
-                    break;
-                case 'f':
-                    BenchmarkRunner.Run<AsyncLockBenchmark>();
+                RenderMenu();
+
+                var key = Console.ReadKey(true);
+
+                if (key.Key == ConsoleKey.DownArrow)
+                {
+                    _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;
+                }
             }
 
+            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)
+            {
+                if (typeof(BaseBenchmark).IsAssignableFrom(type))
+                {
+                    if (type != typeof(BaseBenchmark))
+                    {
+                        benchmarks.Add(type);        
+                    }
+                }
+            }
+
+            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 ({TargetFrameworkProvider.TargetFramework})");
+            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

@@ -0,0 +1,240 @@
+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;
+
+        [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 = MqttPacketFactories.Publish.Create(mqttMessage);
+
+            var buffer = mqttPacketFormatter.Encode(packet);
+            stream = new MemoryStream();
+            stream.Write(buffer.Packet);
+            stream.Write(buffer.Payload);
+            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)
+            {
+                if (formatter == null) throw new ArgumentNullException(nameof(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;
+            }
+        }
+
+    }
+}

Source/MQTTnet.Benchmarks/RoundtripProcessingBenchmark.cs

@@ -8,7 +8,7 @@ namespace MQTTnet.Benchmarks
     [SimpleJob(RuntimeMoniker.Net60)]
     [RPlotExporter, RankColumn]
     [MemoryDiagnoser]
-    public class RoundtripProcessingBenchmark
+    public class RoundtripProcessingBenchmark : BaseBenchmark
     {
         [GlobalSetup]
         public void GlobalSetup()

Source/MQTTnet.Benchmarks/ServerProcessingBenchmark.cs

@@ -1,3 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Tests.Mockups;
@@ -8,7 +12,7 @@ namespace MQTTnet.Benchmarks
     [SimpleJob(RuntimeMoniker.Net60)]
     [RPlotExporter, RankColumn]
     [MemoryDiagnoser]
-    public class ServerProcessingBenchmark
+    public class ServerProcessingBenchmark : BaseBenchmark
     {
         [GlobalSetup]
         public void GlobalSetup()

Source/MQTTnet.Benchmarks/SubscribeBenchmark.cs

@@ -1,3 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Client;
@@ -8,7 +12,7 @@ using System.Linq;
 namespace MQTTnet.Benchmarks
 {
     [MemoryDiagnoser]
-    public class SubscribeBenchmark
+    public class SubscribeBenchmark : BaseBenchmark
     {
         MqttServer _mqttServer;
         IMqttClient _mqttClient;

Source/MQTTnet.Benchmarks/TcpPipesBenchmark.cs

@@ -15,7 +15,7 @@ namespace MQTTnet.Benchmarks
 {
     [SimpleJob(RuntimeMoniker.Net60)]
     [MemoryDiagnoser]
-    public class TcpPipesBenchmark
+    public class TcpPipesBenchmark : BaseBenchmark
     {
         IDuplexPipe _client;
         IDuplexPipe _server;

Source/MQTTnet.Benchmarks/TopicFilterComparerBenchmark.cs

@@ -11,7 +11,7 @@ namespace MQTTnet.Benchmarks
     [SimpleJob(RuntimeMoniker.Net60)]
     [RPlotExporter]
     [MemoryDiagnoser]
-    public class TopicFilterComparerBenchmark
+    public class TopicFilterComparerBenchmark : BaseBenchmark
     {
         static readonly char[] TopicLevelSeparator = { '/' };
 

Source/MQTTnet.Benchmarks/TopicGenerator.cs

@@ -1,31 +1,30 @@
 using System;
 using System.Collections.Generic;
-using System.Text;
 
 namespace MQTTnet.Benchmarks
 {
     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
-           )
+            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));
+            var topicsPerLevel = (int)Math.Pow(numTopicsPerPublisher, 1.0 / 3.0);
             if (topicsPerLevel <= 0)
             {
                 topicsPerLevel = 1;
             }
 
-            int numLevel1Topics = topicsPerLevel;
-            int numLevel2Topics = topicsPerLevel;
+            var numLevel1Topics = topicsPerLevel;
+            var numLevel2Topics = topicsPerLevel;
 
             var maxNumLevel3Topics = 1 + (int)((double)numTopicsPerPublisher / numLevel1Topics / numLevel2Topics);
             if (maxNumLevel3Topics <= 0)
@@ -35,7 +34,7 @@ namespace MQTTnet.Benchmarks
 
             for (var p = 0; p < numPublishers; ++p)
             {
-                int publisherTopicCount = 0;
+                var publisherTopicCount = 0;
                 var publisherName = "pub" + p;
                 for (var l1 = 0; l1 < numLevel1Topics; ++l1)
                 {
@@ -44,19 +43,22 @@ namespace MQTTnet.Benchmarks
                         for (var l3 = 0; l3 < maxNumLevel3Topics; ++l3)
                         {
                             if (publisherTopicCount >= numTopicsPerPublisher)
+                            {
                                 break;
+                            }
 
-                            var topic = string.Format("{0}/building{1}/level{2}/sensor{3}", publisherName, l1 + 1, l2 + 1, l3 + 1);
+                            var topic = $"{publisherName}/building{l1 + 1}/level{l2 + 1}/sensor{l3 + 1}";
                             AddPublisherTopic(publisherName, topic, topicsByPublisher);
 
                             if (l2 == 0)
                             {
-                                var singleWildcardTopic = string.Format("{0}/building{1}/+/sensor{2}", publisherName, l1 + 1, l3 + 1);
+                                var singleWildcardTopic = $"{publisherName}/building{l1 + 1}/+/sensor{l3 + 1}";
                                 AddPublisherTopic(publisherName, singleWildcardTopic, singleWildcardTopicsByPublisher);
                             }
-                            if ((l1 == 0) && (l3 == 0))
+
+                            if (l1 == 0 && l3 == 0)
                             {
-                                var multiWildcardTopic = string.Format("{0}/+/level{1}/+", publisherName, l2 + 1);
+                                var multiWildcardTopic = $"{publisherName}/+/level{l2 + 1}/+";
                                 AddPublisherTopic(publisherName, multiWildcardTopic, multiWildcardTopicsByPublisher);
                             }
 
@@ -75,7 +77,8 @@ namespace MQTTnet.Benchmarks
                 topicList = new List<string>();
                 topicsByPublisher.Add(publisherName, topicList);
             }
+
             topicList.Add(topic);
         }
     }
-}
+}

Source/MQTTnet.Benchmarks/UnsubscribeBenchmark.cs

@@ -1,3 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
 using BenchmarkDotNet.Attributes;
 using MQTTnet.Client;
 using MQTTnet.Server;
@@ -7,7 +11,7 @@ using System.Linq;
 namespace MQTTnet.Benchmarks
 {
     [MemoryDiagnoser]
-    public class UnsubscribeBenchmark
+    public class UnsubscribeBenchmark : BaseBenchmark 
     {
         MqttServer _mqttServer;
         IMqttClient _mqttClient;

Source/MQTTnet.Benchmarks/packages.config

@@ -1,54 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<packages>
-  <package id="BenchmarkDotNet" version="0.10.14" targetFramework="net462" />
-  <package id="BenchmarkDotNet.Core" version="0.10.14" targetFramework="net462" />
-  <package id="BenchmarkDotNet.Toolchains.Roslyn" version="0.10.14" targetFramework="net462" />
-  <package id="Microsoft.CodeAnalysis.Analyzers" version="1.1.0" targetFramework="net462" />
-  <package id="Microsoft.CodeAnalysis.Common" version="2.6.1" targetFramework="net462" />
-  <package id="Microsoft.CodeAnalysis.CSharp" version="2.6.1" targetFramework="net462" />
-  <package id="Microsoft.DotNet.InternalAbstractions" version="1.0.0" targetFramework="net462" />
-  <package id="Microsoft.DotNet.PlatformAbstractions" version="1.1.1" targetFramework="net462" />
-  <package id="Microsoft.Win32.Registry" version="4.3.0" targetFramework="net462" />
-  <package id="System.AppContext" version="4.3.0" targetFramework="net462" />
-  <package id="System.Collections" version="4.3.0" targetFramework="net462" />
-  <package id="System.Collections.Concurrent" version="4.3.0" targetFramework="net462" />
-  <package id="System.Collections.Immutable" version="1.3.1" targetFramework="net462" />
-  <package id="System.Console" version="4.3.0" targetFramework="net462" />
-  <package id="System.Diagnostics.Debug" version="4.3.0" targetFramework="net462" />
-  <package id="System.Diagnostics.FileVersionInfo" version="4.3.0" targetFramework="net462" />
-  <package id="System.Diagnostics.StackTrace" version="4.3.0" targetFramework="net462" />
-  <package id="System.Diagnostics.Tools" version="4.3.0" targetFramework="net462" />
-  <package id="System.Dynamic.Runtime" version="4.3.0" targetFramework="net462" />
-  <package id="System.Globalization" version="4.3.0" targetFramework="net462" />
-  <package id="System.IO.Compression" version="4.3.0" targetFramework="net462" />
-  <package id="System.IO.FileSystem" version="4.3.0" targetFramework="net462" />
-  <package id="System.IO.FileSystem.Primitives" version="4.3.0" targetFramework="net462" />
-  <package id="System.Linq" version="4.3.0" targetFramework="net462" />
-  <package id="System.Linq.Expressions" version="4.3.0" targetFramework="net462" />
-  <package id="System.Reflection" version="4.3.0" targetFramework="net462" />
-  <package id="System.Reflection.Metadata" version="1.4.2" targetFramework="net462" />
-  <package id="System.Resources.ResourceManager" version="4.3.0" targetFramework="net462" />
-  <package id="System.Runtime" version="4.3.0" targetFramework="net462" />
-  <package id="System.Runtime.Extensions" version="4.3.0" targetFramework="net462" />
-  <package id="System.Runtime.InteropServices" version="4.3.0" targetFramework="net462" />
-  <package id="System.Runtime.Numerics" version="4.3.0" targetFramework="net462" />
-  <package id="System.Security.Cryptography.Algorithms" version="4.3.0" targetFramework="net462" />
-  <package id="System.Security.Cryptography.Encoding" version="4.3.0" targetFramework="net462" />
-  <package id="System.Security.Cryptography.Primitives" version="4.3.0" targetFramework="net462" />
-  <package id="System.Security.Cryptography.X509Certificates" version="4.3.0" targetFramework="net462" />
-  <package id="System.Text.Encoding" version="4.3.0" targetFramework="net462" />
-  <package id="System.Text.Encoding.CodePages" version="4.3.0" targetFramework="net462" />
-  <package id="System.Text.Encoding.Extensions" version="4.3.0" targetFramework="net462" />
-  <package id="System.Threading" version="4.3.0" targetFramework="net462" />
-  <package id="System.Threading.Tasks" version="4.3.0" targetFramework="net462" />
-  <package id="System.Threading.Tasks.Extensions" version="4.3.0" targetFramework="net462" />
-  <package id="System.Threading.Tasks.Parallel" version="4.3.0" targetFramework="net462" />
-  <package id="System.Threading.Thread" version="4.3.0" targetFramework="net462" />
-  <package id="System.ValueTuple" version="4.3.0" targetFramework="net462" />
-  <package id="System.Xml.ReaderWriter" version="4.3.0" targetFramework="net462" />
-  <package id="System.Xml.XDocument" version="4.3.0" targetFramework="net462" />
-  <package id="System.Xml.XmlDocument" version="4.3.0" targetFramework="net462" />
-  <package id="System.Xml.XmlSerializer" version="4.3.0" targetFramework="net462" />
-  <package id="System.Xml.XPath" version="4.3.0" targetFramework="net462" />
-  <package id="System.Xml.XPath.XDocument" version="4.3.0" targetFramework="net462" />
-</packages>

Source/MQTTnet.Extensions.ManagedClient/MQTTnet.Extensions.ManagedClient.csproj

@@ -33,7 +33,7 @@
         <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
-        <NoWarn>1591</NoWarn>
+        <NoWarn>1591;NETSDK1138</NoWarn>
     </PropertyGroup>
 
     <PropertyGroup Condition="'$(TargetFramework)' == 'uap10.0'">

Source/MQTTnet.Extensions.Rpc/MQTTnet.Extensions.Rpc.csproj

@@ -33,7 +33,8 @@
         <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
-        <NoWarn>1591</NoWarn>
+        <NoWarn>1591;NETSDK1138</NoWarn>
+        <LangVersion>7.3</LangVersion>
     </PropertyGroup>
 
     <PropertyGroup Condition="'$(TargetFramework)' == 'uap10.0'">

Source/MQTTnet.Extensions.Rpc/MqttFactoryExtensions.cs

@@ -11,10 +11,12 @@ namespace MQTTnet.Extensions.Rpc
     {
         public static IMqttRpcClient CreateMqttRpcClient(this MqttFactory factory, IMqttClient mqttClient)
         {
-            return factory.CreateMqttRpcClient(mqttClient, new MqttRpcClientOptions
-            {
-                TopicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy()
-            });
+            return factory.CreateMqttRpcClient(
+                mqttClient,
+                new MqttRpcClientOptions
+                {
+                    TopicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy()
+                });
         }
 
         public static IMqttRpcClient CreateMqttRpcClient(this MqttFactory _, IMqttClient mqttClient, MqttRpcClientOptions rpcClientOptions)

Source/MQTTnet.Extensions.Rpc/MqttRpcClient.cs

@@ -2,23 +2,24 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using MQTTnet.Client;
-using MQTTnet.Exceptions;
-using MQTTnet.Protocol;
 using System;
 using System.Collections.Concurrent;
 using System.Threading;
 using System.Threading.Tasks;
+using MQTTnet.Client;
+using MQTTnet.Exceptions;
 using MQTTnet.Internal;
+using MQTTnet.Protocol;
 
 namespace MQTTnet.Extensions.Rpc
 {
     public sealed class MqttRpcClient : IMqttRpcClient
     {
-        readonly ConcurrentDictionary<string, TaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, TaskCompletionSource<byte[]>>();
         readonly IMqttClient _mqttClient;
         readonly MqttRpcClientOptions _options;
         
+        readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>>();
+        
         public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
         {
             _mqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
@@ -27,6 +28,18 @@ namespace MQTTnet.Extensions.Rpc
             _mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
         }
 
+        public void Dispose()
+        {
+            _mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
+
+            foreach (var tcs in _waitingCalls)
+            {
+                tcs.Value.TrySetCanceled();
+            }
+
+            _waitingCalls.Clear();
+        }
+
         public async Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel)
         {
             using (var timeoutToken = new CancellationTokenSource(timeout))
@@ -49,15 +62,13 @@ namespace MQTTnet.Extensions.Rpc
 
         public async Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, CancellationToken cancellationToken = default)
         {
-            if (methodName == null) throw new ArgumentNullException(nameof(methodName));
-            
-            var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(new TopicGenerationContext
+            if (methodName == null)
             {
-                MethodName = methodName,
-                QualityOfServiceLevel = qualityOfServiceLevel,
-                MqttClient = _mqttClient,
-                Options = _options
-            });
+                throw new ArgumentNullException(nameof(methodName));
+            }
+
+            var context = new TopicGenerationContext(_mqttClient, _options, methodName, qualityOfServiceLevel);
+            var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(context);
 
             var requestTopic = topicNames.RequestTopic;
             var responseTopic = topicNames.ResponseTopic;
@@ -72,8 +83,7 @@ namespace MQTTnet.Extensions.Rpc
                 throw new MqttProtocolViolationException("RPC response topic is empty.");
             }
 
-            var requestMessage = new MqttApplicationMessageBuilder()
-                .WithTopic(requestTopic)
+            var requestMessage = new MqttApplicationMessageBuilder().WithTopic(requestTopic)
                 .WithPayload(payload)
                 .WithQualityOfServiceLevel(qualityOfServiceLevel)
                 .WithResponseTopic(responseTopic)
@@ -81,25 +91,23 @@ namespace MQTTnet.Extensions.Rpc
 
             try
             {
-#if NET452
-                var awaitable = new TaskCompletionSource<byte[]>();
-#else
-                var awaitable = new TaskCompletionSource<byte[]>(TaskCreationOptions.RunContinuationsAsynchronously);
-#endif
+                var awaitable = new AsyncTaskCompletionSource<byte[]>();
 
                 if (!_waitingCalls.TryAdd(responseTopic, awaitable))
                 {
                     throw new InvalidOperationException();
                 }
 
-                var subscribeOptions = new MqttClientSubscribeOptionsBuilder()
-                    .WithTopicFilter(responseTopic, qualityOfServiceLevel)
-                    .Build();
+                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(); }))
+                using (cancellationToken.Register(
+                           () =>
+                           {
+                               awaitable.TrySetCanceled();
+                           }))
                 {
                     return await awaitable.Task.ConfigureAwait(false);
                 }
@@ -107,8 +115,8 @@ namespace MQTTnet.Extensions.Rpc
             finally
             {
                 _waitingCalls.TryRemove(responseTopic, out _);
-                
-                await _mqttClient.UnsubscribeAsync(responseTopic).ConfigureAwait(false);
+
+                await _mqttClient.UnsubscribeAsync(responseTopic, CancellationToken.None).ConfigureAwait(false);
             }
         }
 
@@ -119,28 +127,12 @@ namespace MQTTnet.Extensions.Rpc
                 return CompletedTask.Instance;
             }
 
-#if NET452
-            Task.Run(() => awaitable.TrySetResult(eventArgs.ApplicationMessage.Payload));
-#else
             awaitable.TrySetResult(eventArgs.ApplicationMessage.Payload);
-#endif
 
             // Set this message to handled to that other code can avoid execution etc.
             eventArgs.IsHandled = true;
 
             return CompletedTask.Instance;
         }
-
-        public void Dispose()
-        {
-            _mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
-
-            foreach (var tcs in _waitingCalls)
-            {
-                tcs.Value.TrySetCanceled();
-            }
-
-            _waitingCalls.Clear();
-        }
     }
 }

Source/MQTTnet.Extensions.Rpc/Options/MqttRpcClientOptionsBuilder.cs

@@ -10,13 +10,6 @@ namespace MQTTnet.Extensions.Rpc
     {
         IMqttRpcClientTopicGenerationStrategy _topicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy();
 
-        public MqttRpcClientOptionsBuilder WithTopicGenerationStrategy(IMqttRpcClientTopicGenerationStrategy value)
-        {
-            _topicGenerationStrategy = value ?? throw new ArgumentNullException(nameof(value));
-
-            return this;
-        }
-
         public MqttRpcClientOptions Build()
         {
             return new MqttRpcClientOptions
@@ -24,5 +17,12 @@ namespace MQTTnet.Extensions.Rpc
                 TopicGenerationStrategy = _topicGenerationStrategy
             };
         }
+
+        public MqttRpcClientOptionsBuilder WithTopicGenerationStrategy(IMqttRpcClientTopicGenerationStrategy value)
+        {
+            _topicGenerationStrategy = value ?? throw new ArgumentNullException(nameof(value));
+
+            return this;
+        }
     }
-}
+}

Source/MQTTnet.Extensions.Rpc/Options/TopicGeneration/DefaultMqttRpcClientTopicGenerationStrategy.cs

@@ -10,6 +10,11 @@ namespace MQTTnet.Extensions.Rpc
     {
         public MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context)
         {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
             if (context.MethodName.Contains("/") || context.MethodName.Contains("+") || context.MethodName.Contains("#"))
             {
                 throw new ArgumentException("The method name cannot contain /, + or #.");

Source/MQTTnet.Extensions.Rpc/Options/TopicGeneration/TopicGenerationContext.cs

@@ -2,6 +2,7 @@
 // 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.Client;
 using MQTTnet.Protocol;
 
@@ -9,20 +10,29 @@ namespace MQTTnet.Extensions.Rpc
 {
     public sealed class TopicGenerationContext
     {
-        public string MethodName { get; set; }
+        public TopicGenerationContext(IMqttClient mqttClient, MqttRpcClientOptions options, string methodName, MqttQualityOfServiceLevel qualityOfServiceLevel)
+        {
+            MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
+            QualityOfServiceLevel = qualityOfServiceLevel;
+            MqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
+            Options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public string MethodName { 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).
+        ///     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; set; }
-
-        public IMqttClient MqttClient { get; set; }
-
-        public MqttRpcClientOptions Options { get; set; }
+        public MqttQualityOfServiceLevel QualityOfServiceLevel { get; }
     }
-}
+}

Source/MQTTnet.Extensions.WebSocket4Net/MQTTnet.Extensions.WebSocket4Net.csproj

@@ -33,7 +33,8 @@
         <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
-        <NoWarn>1591</NoWarn>
+        <NoWarn>1591;NETSDK1138</NoWarn>
+        <LangVersion>7.3</LangVersion>
     </PropertyGroup>
 
     <PropertyGroup Condition="'$(TargetFramework)' == 'uap10.0'">

Source/MQTTnet.Extensions.WebSocket4Net/MqttFactoryExtensions.cs

@@ -10,9 +10,12 @@ namespace MQTTnet.Extensions.WebSocket4Net
     {
         public static MqttFactory UseWebSocket4Net(this MqttFactory mqttFactory)
         {
-            if (mqttFactory == null) throw new ArgumentNullException(nameof(mqttFactory));
+            if (mqttFactory == null)
+            {
+                throw new ArgumentNullException(nameof(mqttFactory));
+            }
 
             return mqttFactory.UseClientAdapterFactory(new WebSocket4NetMqttClientAdapterFactory());
         }
     }
-}
+}

Source/MQTTnet.Extensions.WebSocket4Net/WebSocket4NetMqttChannel.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Net;
 using System.Security.Authentication;
@@ -17,14 +18,14 @@ using MQTTnet.Exceptions;
 using MQTTnet.Internal;
 using SuperSocket.ClientEngine;
 using WebSocket4Net;
+using DataReceivedEventArgs = WebSocket4Net.DataReceivedEventArgs;
 
 namespace MQTTnet.Extensions.WebSocket4Net
 {
     public sealed class WebSocket4NetMqttChannel : IMqttChannel
     {
-        readonly BlockingCollection<byte> _receiveBuffer = new BlockingCollection<byte>();
-
         readonly MqttClientOptions _clientOptions;
+        readonly BlockingCollection<byte> _receiveBuffer = new BlockingCollection<byte>();
         readonly MqttClientWebSocketOptions _webSocketOptions;
 
         WebSocket _webSocket;
@@ -35,13 +36,13 @@ namespace MQTTnet.Extensions.WebSocket4Net
             _webSocketOptions = webSocketOptions ?? throw new ArgumentNullException(nameof(webSocketOptions));
         }
 
+        public X509Certificate2 ClientCertificate { get; }
+
         public string Endpoint => _webSocketOptions.Uri;
 
         public bool IsSecureConnection { get; private set; }
 
-        public X509Certificate2 ClientCertificate { get; }
-
-        public async Task ConnectAsync(CancellationToken cancellationToken)
+        public Task ConnectAsync(CancellationToken cancellationToken)
         {
             var uri = _webSocketOptions.Uri;
             if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase) && !uri.StartsWith("wss://", StringComparison.OrdinalIgnoreCase))
@@ -55,11 +56,13 @@ namespace MQTTnet.Extensions.WebSocket4Net
                     uri = "wss://" + uri;
                 }
             }
+            
+            IsSecureConnection = uri.StartsWith("wss://", StringComparison.OrdinalIgnoreCase);
 
-#if NET48 || NETCOREAPP3_1 || NET5 || NET6
-            var sslProtocols = _webSocketOptions?.TlsOptions?.SslProtocol ?? SslProtocols.Tls12 | SslProtocols.Tls13;
+#if NET48 || NETCOREAPP3_0_OR_GREATER
+            var sslProtocols = _webSocketOptions.TlsOptions?.SslProtocol ?? SslProtocols.Tls12 | SslProtocols.Tls13;
 #else
-            var sslProtocols = _webSocketOptions?.TlsOptions?.SslProtocol ?? SslProtocols.Tls12 | (SslProtocols)0x00003000 /*Tls13*/;
+            var sslProtocols = _webSocketOptions.TlsOptions?.SslProtocol ?? SslProtocols.Tls12 | (SslProtocols)0x00003000 /*Tls13*/;
 #endif
 
             var subProtocol = _webSocketOptions.SubProtocols.FirstOrDefault() ?? string.Empty;
@@ -90,7 +93,7 @@ namespace MQTTnet.Extensions.WebSocket4Net
             var receiveBufferSize = 0;
 
             var certificates = new X509CertificateCollection();
-            if (_webSocketOptions?.TlsOptions?.Certificates != null)
+            if (_webSocketOptions.TlsOptions?.Certificates != null)
             {
                 foreach (var certificate in _webSocketOptions.TlsOptions.Certificates)
                 {
@@ -107,15 +110,13 @@ namespace MQTTnet.Extensions.WebSocket4Net
                 NoDelay = true,
                 Security =
                 {
-                    AllowUnstrustedCertificate = _webSocketOptions?.TlsOptions?.AllowUntrustedCertificates == true,
-                    AllowCertificateChainErrors = _webSocketOptions?.TlsOptions?.IgnoreCertificateChainErrors == true,
+                    AllowUnstrustedCertificate = _webSocketOptions.TlsOptions?.AllowUntrustedCertificates == true,
+                    AllowCertificateChainErrors = _webSocketOptions.TlsOptions?.IgnoreCertificateChainErrors == true,
                     Certificates = certificates
                 }
             };
 
-            await ConnectInternalAsync(cancellationToken).ConfigureAwait(false);
-            
-            IsSecureConnection = uri.StartsWith("wss://", StringComparison.OrdinalIgnoreCase);
+            return ConnectInternalAsync(cancellationToken);
         }
 
         public Task DisconnectAsync(CancellationToken cancellationToken)
@@ -124,10 +125,23 @@ namespace MQTTnet.Extensions.WebSocket4Net
             {
                 _webSocket.Close();
             }
-            
+
             return CompletedTask.Instance;
         }
 
+        public void Dispose()
+        {
+            if (_webSocket == null)
+            {
+                return;
+            }
+
+            _webSocket.DataReceived -= OnDataReceived;
+            _webSocket.Error -= OnError;
+            _webSocket.Dispose();
+            _webSocket = null;
+        }
+
         public Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
         {
             var readBytes = 0;
@@ -161,75 +175,55 @@ namespace MQTTnet.Extensions.WebSocket4Net
             return CompletedTask.Instance;
         }
 
-        public void Dispose()
-        {
-            if (_webSocket == null)
-            {
-                return;
-            }
-
-            _webSocket.DataReceived -= OnDataReceived;
-            _webSocket.Error -= OnError;
-            _webSocket.Dispose();
-            _webSocket = null;
-        }
-
-        static void OnError(object sender, ErrorEventArgs e)
-        {
-            System.Diagnostics.Debug.Write(e.Exception.ToString());
-        }
-
-        void OnDataReceived(object sender, DataReceivedEventArgs e)
-        {
-            foreach (var @byte in e.Data)
-            {
-                _receiveBuffer.Add(@byte);
-            }
-        }
-
         async Task ConnectInternalAsync(CancellationToken cancellationToken)
         {
             _webSocket.Error += OnError;
             _webSocket.DataReceived += OnDataReceived;
 
-            var taskCompletionSource = new TaskCompletionSource<Exception>();
+            var promise = new AsyncTaskCompletionSource<bool>();
 
             void ErrorHandler(object sender, ErrorEventArgs e)
             {
-                taskCompletionSource.TrySetResult(e.Exception);
+                promise.TrySetException(e.Exception);
             }
 
-            void SuccessHandler(object sender, EventArgs e)
+            void OpenedHandler(object sender, EventArgs e)
             {
-                taskCompletionSource.TrySetResult(null);
+                promise.TrySetResult(true);
+            }
+
+            void ClosedHandler(object sender, EventArgs e)
+            {
+                promise.TrySetException(new MqttCommunicationException("Connection closed."));
             }
 
             try
             {
-                _webSocket.Opened += SuccessHandler;
+                _webSocket.Opened += OpenedHandler;
+                _webSocket.Closed += ClosedHandler;
                 _webSocket.Error += ErrorHandler;
 
-#pragma warning disable AsyncFixer02 // Long-running or blocking operations inside an async method
-                _webSocket.Open();
-#pragma warning restore AsyncFixer02 // Long-running or blocking operations inside an async method
-
-                using (var timeoutCts = new CancellationTokenSource(_clientOptions.Timeout))
-                using (var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(timeoutCts.Token, cancellationToken))
+                using (var timeout = new CancellationTokenSource(_clientOptions.Timeout))
+                using (var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(timeout.Token, cancellationToken))
                 {
-                    using (linkedCts.Token.Register(() => taskCompletionSource.TrySetCanceled()))
+                    using (linkedCts.Token.Register(() => promise.TrySetCanceled()))
                     {
                         try
                         {
-                            await taskCompletionSource.Task.ConfigureAwait(false);
+                            // OpenAsync does basically the same but without support for a cancellation token.
+                            // So we do it on our own!
+                            _webSocket.Open();
+
+                            await promise.Task.ConfigureAwait(false);
                         }
                         catch (Exception exception)
                         {
-                            var timeoutReached = timeoutCts.IsCancellationRequested && !cancellationToken.IsCancellationRequested;
+                            var timeoutReached = timeout.IsCancellationRequested && !cancellationToken.IsCancellationRequested;
                             if (timeoutReached)
                             {
                                 throw new MqttCommunicationTimedOutException(exception);
                             }
-                            
+
                             if (exception is AuthenticationException authenticationException)
                             {
                                 throw new MqttCommunicationException(authenticationException.InnerException);
@@ -251,9 +245,23 @@ namespace MQTTnet.Extensions.WebSocket4Net
             }
             finally
             {
-                _webSocket.Opened -= SuccessHandler;
+                _webSocket.Opened -= OpenedHandler;
+                _webSocket.Closed -= ClosedHandler;
                 _webSocket.Error -= ErrorHandler;
             }
         }
+
+        void OnDataReceived(object sender, DataReceivedEventArgs e)
+        {
+            foreach (var @byte in e.Data)
+            {
+                _receiveBuffer.Add(@byte);
+            }
+        }
+
+        static void OnError(object sender, ErrorEventArgs e)
+        {
+            Debug.Write(e.Exception.ToString());
+        }
     }
-}
+}

Source/MQTTnet.Extensions.WebSocket4Net/WebSocket4NetMqttClientAdapterFactory.cs

@@ -2,12 +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.
 
-using MQTTnet.Adapter;
-using MQTTnet.Formatter;
-using MQTTnet.Implementations;
 using System;
+using MQTTnet.Adapter;
 using MQTTnet.Client;
 using MQTTnet.Diagnostics;
+using MQTTnet.Formatter;
+using MQTTnet.Implementations;
 
 namespace MQTTnet.Extensions.WebSocket4Net
 {
@@ -15,7 +15,10 @@ namespace MQTTnet.Extensions.WebSocket4Net
     {
         public IMqttChannelAdapter CreateClientAdapter(MqttClientOptions options, MqttPacketInspector packetInspector, IMqttNetLogger logger)
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
+            if (options == null)
+            {
+                throw new ArgumentNullException(nameof(options));
+            }
 
             switch (options.ChannelOptions)
             {
@@ -23,7 +26,7 @@ namespace MQTTnet.Extensions.WebSocket4Net
                 {
                     return new MqttChannelAdapter(
                         new MqttTcpChannel(options),
-                        new MqttPacketFormatterAdapter(options.ProtocolVersion, new MqttBufferWriter(4096, 65535)),
+                        new MqttPacketFormatterAdapter(options.ProtocolVersion, new MqttBufferWriter(options.WriterBufferSize, options.WriterBufferSizeMax)),
                         packetInspector,
                         logger);
                 }
@@ -32,16 +35,16 @@ namespace MQTTnet.Extensions.WebSocket4Net
                 {
                     return new MqttChannelAdapter(
                         new WebSocket4NetMqttChannel(options, webSocketOptions),
-                        new MqttPacketFormatterAdapter(options.ProtocolVersion, new MqttBufferWriter(4068, 65535)), 
+                        new MqttPacketFormatterAdapter(options.ProtocolVersion, new MqttBufferWriter(options.WriterBufferSize, options.WriterBufferSizeMax)),
                         packetInspector,
                         logger);
                 }
 
                 default:
-                    {
-                        throw new NotSupportedException();
-                    }
+                {
+                    throw new NotSupportedException();
+                }
             }
         }
     }
-}
+}

Source/MQTTnet.TestApp/MQTTnet.TestApp.csproj

@@ -9,12 +9,11 @@
         <EnableNETAnalyzers>false</EnableNETAnalyzers>
         <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
+        <NoWarn>1591;NETSDK1138</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
-        <PackageReference Include="Microsoft.CodeAnalysis.Compilers" Version="4.0.1" />
-        <PackageReference Include="Microsoft.Net.Compilers" Version="4.0.1" />
+        <PackageReference Include="Newtonsoft.Json" Version="13.0.2" />
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.TestApp/PublicBrokerTest.cs

@@ -2,11 +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.
 
-using MQTTnet.Client;
 using System;
 using System.Security.Authentication;
 using System.Threading;
 using System.Threading.Tasks;
+using MQTTnet.Client;
+using MQTTnet.Extensions.WebSocket4Net;
 using MQTTnet.Formatter;
 using MQTTnet.Internal;
 using MQTTnet.Protocol;
@@ -17,10 +18,6 @@ namespace MQTTnet.TestApp
     {
         public static async Task RunAsync()
         {
-            // MqttNetConsoleLogger.ForwardToConsole();
-
-            // For most of these connections to work, set output target to Net5.0.            
-
 #if NET5_0_OR_GREATER
             // TLS13 is only available in Net5.0
             var unsafeTls13 = new MqttClientOptionsBuilderTlsParameters
@@ -31,7 +28,6 @@ namespace MQTTnet.TestApp
                 CertificateValidationHandler = w => true
             };
 #endif
-
             // Also defining TLS12 for servers that don't seem no to support TLS13.
             var unsafeTls12 = new MqttClientOptionsBuilderTlsParameters
             {
@@ -42,33 +38,37 @@ namespace MQTTnet.TestApp
             };
 
             // mqtt.eclipseprojects.io
-            await ExecuteTestAsync("mqtt.eclipseprojects.io TCP",
-                    new MqttClientOptionsBuilder().WithTcpServer("mqtt.eclipseprojects.io", 1883)
-                        .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "mqtt.eclipseprojects.io TCP",
+                new MqttClientOptionsBuilder().WithTcpServer("mqtt.eclipseprojects.io", 1883).WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("mqtt.eclipseprojects.io WS",
-                new MqttClientOptionsBuilder().WithWebSocketServer("mqtt.eclipseprojects.io:80/mqtt")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "mqtt.eclipseprojects.io WS",
+                new MqttClientOptionsBuilder().WithWebSocketServer("mqtt.eclipseprojects.io:80/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
 #if NET5_0_OR_GREATER
             await ExecuteTestAsync("mqtt.eclipseprojects.io WS TLS13",
                 new MqttClientOptionsBuilder().WithWebSocketServer("mqtt.eclipseprojects.io:443/mqtt")
                     .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls13).Build());
+            
+            await ExecuteTestAsync("mqtt.eclipseprojects.io WS TLS13 (WebSocket4Net)",
+                new MqttClientOptionsBuilder().WithWebSocketServer("mqtt.eclipseprojects.io:443/mqtt")
+                    .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls13).Build(),
+                    true);
 #endif
 
             // test.mosquitto.org
-            await ExecuteTestAsync("test.mosquitto.org TCP",
-                new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 1883)
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "test.mosquitto.org TCP",
+                new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 1883).WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("test.mosquitto.org TCP - Authenticated",
-                new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 1884)
-                    .WithCredentials("rw", "readwrite")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "test.mosquitto.org TCP - Authenticated",
+                new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 1884).WithCredentials("rw", "readwrite").WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("test.mosquitto.org TCP TLS12",
-                new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883)
-                    .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+            await ExecuteTestAsync(
+                "test.mosquitto.org TCP TLS12",
+                new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883).WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
 
 #if NET5_0_OR_GREATER
             await ExecuteTestAsync("test.mosquitto.org TCP TLS13",
@@ -76,27 +76,40 @@ namespace MQTTnet.TestApp
                     .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls13).Build());
 #endif
 
-            await ExecuteTestAsync("test.mosquitto.org TCP TLS12 - Authenticated",
+            await ExecuteTestAsync(
+                "test.mosquitto.org TCP TLS12 - Authenticated",
                 new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8885)
                     .WithCredentials("rw", "readwrite")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+                    .WithProtocolVersion(MqttProtocolVersion.V311)
+                    .WithTls(unsafeTls12)
+                    .Build());
 
-            await ExecuteTestAsync("test.mosquitto.org WS",
-                new MqttClientOptionsBuilder().WithWebSocketServer("test.mosquitto.org:8080/mqtt")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "test.mosquitto.org WS",
+                new MqttClientOptionsBuilder().WithWebSocketServer("test.mosquitto.org:8080/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("test.mosquitto.org WS TLS12",
-                new MqttClientOptionsBuilder().WithWebSocketServer("test.mosquitto.org:8081/mqtt")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+            await ExecuteTestAsync(
+                "test.mosquitto.org WS (WebSocket4Net)",
+                new MqttClientOptionsBuilder().WithWebSocketServer("test.mosquitto.org:8080/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build(),
+                true);
+
+            await ExecuteTestAsync(
+                "test.mosquitto.org WS TLS12",
+                new MqttClientOptionsBuilder().WithWebSocketServer("test.mosquitto.org:8081/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+
+            // await ExecuteTestAsync(
+            //     "test.mosquitto.org WS TLS12 (WebSocket4Net)",
+            //     new MqttClientOptionsBuilder().WithWebSocketServer("test.mosquitto.org:8081/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build(),
+            //     true);
 
             // broker.emqx.io
-            await ExecuteTestAsync("broker.emqx.io TCP",
-                new MqttClientOptionsBuilder().WithTcpServer("broker.emqx.io", 1883)
-                     .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "broker.emqx.io TCP",
+                new MqttClientOptionsBuilder().WithTcpServer("broker.emqx.io", 1883).WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("broker.emqx.io TCP TLS12",
-                new MqttClientOptionsBuilder().WithTcpServer("broker.emqx.io", 8883)
-                    .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+            await ExecuteTestAsync(
+                "broker.emqx.io TCP TLS12",
+                new MqttClientOptionsBuilder().WithTcpServer("broker.emqx.io", 8883).WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
 
 #if NET5_0_OR_GREATER
             await ExecuteTestAsync("broker.emqx.io TCP TLS13",
@@ -104,23 +117,37 @@ namespace MQTTnet.TestApp
                     .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls13).Build());
 #endif
 
-            await ExecuteTestAsync("broker.emqx.io WS",
-                new MqttClientOptionsBuilder().WithWebSocketServer("broker.emqx.io:8083/mqtt")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "broker.emqx.io WS",
+                new MqttClientOptionsBuilder().WithWebSocketServer("broker.emqx.io:8083/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("broker.emqx.io WS TLS12",
-                new MqttClientOptionsBuilder().WithWebSocketServer("broker.emqx.io:8084/mqtt")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+            await ExecuteTestAsync(
+                "broker.emqx.io WS (WebSocket4Net)",
+                new MqttClientOptionsBuilder().WithWebSocketServer("broker.emqx.io:8084/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build(),
+                true);
 
+            await ExecuteTestAsync(
+                "broker.emqx.io WS TLS12",
+                new MqttClientOptionsBuilder().WithWebSocketServer("broker.emqx.io:8084/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build());
+
+            await ExecuteTestAsync(
+                "broker.emqx.io WS TLS12 (WebSocket4Net)",
+                new MqttClientOptionsBuilder().WithWebSocketServer("broker.emqx.io:8084/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).WithTls(unsafeTls12).Build(),
+                true);
 
             // broker.hivemq.com
-            await ExecuteTestAsync("broker.hivemq.com TCP",
-                new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com", 1883)
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "broker.hivemq.com TCP",
+                new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com", 1883).WithProtocolVersion(MqttProtocolVersion.V311).Build());
 
-            await ExecuteTestAsync("broker.hivemq.com WS",
-                new MqttClientOptionsBuilder().WithWebSocketServer("broker.hivemq.com:8000/mqtt")
-                    .WithProtocolVersion(MqttProtocolVersion.V311).Build());
+            await ExecuteTestAsync(
+                "broker.hivemq.com WS",
+                new MqttClientOptionsBuilder().WithWebSocketServer("broker.hivemq.com:8000/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build());
+
+            await ExecuteTestAsync(
+                "broker.hivemq.com WS (WebSocket4Net)",
+                new MqttClientOptionsBuilder().WithWebSocketServer("broker.hivemq.com:8000/mqtt").WithProtocolVersion(MqttProtocolVersion.V311).Build(),
+                true);
 
             // mqtt.swifitch.cz: Does not seem to operate any more
 
@@ -130,36 +157,43 @@ namespace MQTTnet.TestApp
             Console.ReadLine();
         }
 
-        static async Task ExecuteTestAsync(string name, MqttClientOptions options)
+        static async Task ExecuteTestAsync(string name, MqttClientOptions options, bool useWebSocket4Net = false)
         {
             try
             {
                 Write("Testing '" + name + "'... ", ConsoleColor.Gray);
+
                 var factory = new MqttFactory();
-                //factory.UseWebSocket4Net();
-                var client = factory.CreateMqttClient();
-                var topic = Guid.NewGuid().ToString();
-
-                MqttApplicationMessage receivedMessage = null;
-                client.ApplicationMessageReceivedAsync += e =>
+                if (useWebSocket4Net)
                 {
-                    receivedMessage = e.ApplicationMessage;
-                    return CompletedTask.Instance;
-                };
-
-                await client.ConnectAsync(options);
-                await client.SubscribeAsync(topic, MqttQualityOfServiceLevel.AtLeastOnce);
-                await client.PublishStringAsync(topic, "Hello_World", MqttQualityOfServiceLevel.AtLeastOnce);
-
-                SpinWait.SpinUntil(() => receivedMessage != null, 5000);
-
-                if (receivedMessage?.Topic != topic || receivedMessage?.ConvertPayloadToString() != "Hello_World")
-                {
-                    throw new Exception("Message invalid.");
+                    factory.UseWebSocket4Net();
                 }
 
-                await client.UnsubscribeAsync(topic);
-                await client.DisconnectAsync();
+                using (var client = factory.CreateMqttClient())
+                {
+                    MqttApplicationMessage receivedMessage = null;
+                    client.ApplicationMessageReceivedAsync += e =>
+                    {
+                        receivedMessage = e.ApplicationMessage;
+                        return CompletedTask.Instance;
+                    };
+
+                    await client.ConnectAsync(options).ConfigureAwait(false);
+
+                    var topic = Guid.NewGuid().ToString();
+                    await client.SubscribeAsync(topic, MqttQualityOfServiceLevel.AtLeastOnce).ConfigureAwait(false);
+                    await client.PublishStringAsync(topic, "Hello_World", MqttQualityOfServiceLevel.AtLeastOnce).ConfigureAwait(false);
+
+                    SpinWait.SpinUntil(() => receivedMessage != null, 5000);
+
+                    if (receivedMessage?.Topic != topic || receivedMessage?.ConvertPayloadToString() != "Hello_World")
+                    {
+                        throw new Exception("Message invalid.");
+                    }
+
+                    await client.UnsubscribeAsync(topic).ConfigureAwait(false);
+                    await client.DisconnectAsync().ConfigureAwait(false);
+                }
 
                 Write("[OK]\n", ConsoleColor.Green);
             }
@@ -174,6 +208,5 @@ namespace MQTTnet.TestApp
             Console.ForegroundColor = color;
             Console.Write(message);
         }
-
     }
-}
+}

Source/MQTTnet.Tests/Client/ManagedMqttClient_Tests.cs

@@ -47,10 +47,12 @@ namespace MQTTnet.Tests.Client
 
                 await managedClient.StartAsync(managedClientOptions);
                 await LongTestDelay();
+                await LongTestDelay();
                 
                 // Send test data.
                 await senderClient.PublishStringAsync("topic1");
                 await LongTestDelay();
+                await LongTestDelay();
                 
                 receivedMessages.AssertReceivedCountEquals(1);
 
@@ -329,13 +331,7 @@ namespace MQTTnet.Tests.Client
                 await testEnvironment.StartServer().ConfigureAwait(false);
 
                 var sendingClient = await testEnvironment.ConnectClient().ConfigureAwait(false);
-                await sendingClient.PublishAsync(
-                    new MqttApplicationMessage
-                    {
-                        Topic = "topic",
-                        Payload = new byte[] { 1 },
-                        Retain = true
-                    });
+                await sendingClient.PublishStringAsync("topic", "A", retain: true);
 
                 // Wait a bit for the retained message to be available
                 await LongTestDelay();
@@ -357,18 +353,15 @@ namespace MQTTnet.Tests.Client
 
                 await managedClient.SubscribeAsync("topic");
 
-                await managedClient.StartAsync(new ManagedMqttClientOptionsBuilder().WithClientOptions(clientOptions).WithAutoReconnectDelay(TimeSpan.FromSeconds(1)).Build());
-
+                await managedClient.StartAsync(new ManagedMqttClientOptionsBuilder().WithClientOptions(clientOptions).WithAutoReconnectDelay(TimeSpan.FromSeconds(0.5)).Build());
                 await LongTestDelay();
 
                 Assert.AreEqual(1, receivedManagedMessages.Count);
 
                 await managedClient.StopAsync();
-
                 await LongTestDelay();
 
-                await managedClient.StartAsync(new ManagedMqttClientOptionsBuilder().WithClientOptions(clientOptions).WithAutoReconnectDelay(TimeSpan.FromSeconds(1)).Build());
-
+                await managedClient.StartAsync(new ManagedMqttClientOptionsBuilder().WithClientOptions(clientOptions).WithAutoReconnectDelay(TimeSpan.FromSeconds(0.5)).Build());
                 await LongTestDelay();
 
                 // After reconnect and then some delay, the retained message must not be received,
@@ -377,7 +370,6 @@ namespace MQTTnet.Tests.Client
 
                 // Make sure that it gets received after subscribing again.
                 await managedClient.SubscribeAsync("topic");
-                
                 await LongTestDelay();
                 
                 Assert.AreEqual(2, receivedManagedMessages.Count);

Source/MQTTnet.Tests/Extensions/Rpc_Tests.cs

@@ -6,68 +6,93 @@ using System;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
-using MQTTnet.Tests.Mockups;
 using MQTTnet.Client;
 using MQTTnet.Exceptions;
 using MQTTnet.Extensions.Rpc;
-using MQTTnet.Protocol;
 using MQTTnet.Formatter;
-using MQTTnet.Implementations;
 using MQTTnet.Internal;
+using MQTTnet.Protocol;
+using MQTTnet.Tests.Mockups;
 
-namespace MQTTnet.Tests
+namespace MQTTnet.Tests.Extensions
 {
     [TestClass]
-    public sealed class RPC_Tests : BaseTestClass
+    public sealed class Rpc_Tests : BaseTestClass
     {
+        [TestMethod]
+        public async Task Execute_Success_MQTT_V5_Mixed_Clients()
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                await testEnvironment.StartServer();
+                var responseSender = await testEnvironment.ConnectClient();
+                await responseSender.SubscribeAsync("MQTTnet.RPC/+/ping");
+
+                responseSender.ApplicationMessageReceivedAsync += async e =>
+                {
+                    Assert.IsNull(e.ApplicationMessage.ResponseTopic);
+                    await responseSender.PublishStringAsync(e.ApplicationMessage.Topic + "/response", "pong");
+                };
+
+                var requestSender = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithProtocolVersion(MqttProtocolVersion.V500));
+
+                using (var rpcClient = new MqttRpcClient(requestSender, new MqttRpcClientOptionsBuilder().Build()))
+                {
+                    var response = await rpcClient.ExecuteAsync(TimeSpan.FromSeconds(5), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
+
+                    Assert.AreEqual("pong", Encoding.UTF8.GetString(response));
+                }
+            }
+        }
+
         [TestMethod]
         public Task Execute_Success_With_QoS_0()
         {
             return Execute_Success(MqttQualityOfServiceLevel.AtMostOnce, MqttProtocolVersion.V311);
         }
 
-        [TestMethod]
-        public Task Execute_Success_With_QoS_1()
-        {
-            return Execute_Success(MqttQualityOfServiceLevel.AtLeastOnce, MqttProtocolVersion.V311);
-        }
-
-        [TestMethod]
-        public Task Execute_Success_With_QoS_2()
-        {
-            return Execute_Success(MqttQualityOfServiceLevel.ExactlyOnce, MqttProtocolVersion.V311);
-        }
-
         [TestMethod]
         public Task Execute_Success_With_QoS_0_MQTT_V5()
         {
             return Execute_Success(MqttQualityOfServiceLevel.AtMostOnce, MqttProtocolVersion.V500);
         }
 
-        [TestMethod]
-        public Task Execute_Success_With_QoS_1_MQTT_V5()
-        {
-            return Execute_Success(MqttQualityOfServiceLevel.AtLeastOnce, MqttProtocolVersion.V500);
-        }
-
-        [TestMethod]
-        public Task Execute_Success_With_QoS_2_MQTT_V5()
-        {
-            return Execute_Success(MqttQualityOfServiceLevel.ExactlyOnce, MqttProtocolVersion.V500);
-        }
-
         [TestMethod]
         public Task Execute_Success_With_QoS_0_MQTT_V5_Use_ResponseTopic()
         {
             return Execute_Success_MQTT_V5(MqttQualityOfServiceLevel.AtMostOnce);
         }
 
+        [TestMethod]
+        public Task Execute_Success_With_QoS_1()
+        {
+            return Execute_Success(MqttQualityOfServiceLevel.AtLeastOnce, MqttProtocolVersion.V311);
+        }
+
+        [TestMethod]
+        public Task Execute_Success_With_QoS_1_MQTT_V5()
+        {
+            return Execute_Success(MqttQualityOfServiceLevel.AtLeastOnce, MqttProtocolVersion.V500);
+        }
+
         [TestMethod]
         public Task Execute_Success_With_QoS_1_MQTT_V5_Use_ResponseTopic()
         {
             return Execute_Success_MQTT_V5(MqttQualityOfServiceLevel.AtLeastOnce);
         }
 
+        [TestMethod]
+        public Task Execute_Success_With_QoS_2()
+        {
+            return Execute_Success(MqttQualityOfServiceLevel.ExactlyOnce, MqttProtocolVersion.V311);
+        }
+
+        [TestMethod]
+        public Task Execute_Success_With_QoS_2_MQTT_V5()
+        {
+            return Execute_Success(MqttQualityOfServiceLevel.ExactlyOnce, MqttProtocolVersion.V500);
+        }
+
         [TestMethod]
         public Task Execute_Success_With_QoS_2_MQTT_V5_Use_ResponseTopic()
         {
@@ -90,6 +115,31 @@ namespace MQTTnet.Tests
             }
         }
 
+        [TestMethod]
+        [ExpectedException(typeof(MqttCommunicationTimedOutException))]
+        public async Task Execute_Timeout_MQTT_V5_Mixed_Clients()
+        {
+            using (var testEnvironment = new TestEnvironment(TestContext))
+            {
+                await testEnvironment.StartServer();
+                var responseSender = await testEnvironment.ConnectClient();
+                await responseSender.SubscribeAsync("MQTTnet.RPC/+/ping");
+
+                responseSender.ApplicationMessageReceivedAsync += async e =>
+                {
+                    Assert.IsNull(e.ApplicationMessage.ResponseTopic);
+                    await CompletedTask.Instance;
+                };
+
+                var requestSender = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithProtocolVersion(MqttProtocolVersion.V500));
+
+                using (var rpcClient = new MqttRpcClient(requestSender, new MqttRpcClientOptionsBuilder().Build()))
+                {
+                    var response = await rpcClient.ExecuteAsync(TimeSpan.FromSeconds(2), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
+                }
+            }
+        }
+
         [TestMethod]
         [ExpectedException(typeof(MqttCommunicationTimedOutException))]
         public async Task Execute_With_Custom_Topic_Names()
@@ -98,14 +148,24 @@ namespace MQTTnet.Tests
             {
                 await testEnvironment.StartServer();
 
-                var requestSender = await testEnvironment.ConnectClient();
-
                 var rpcClient = await testEnvironment.ConnectRpcClient(new MqttRpcClientOptionsBuilder().WithTopicGenerationStrategy(new TestTopicStrategy()).Build());
 
                 await rpcClient.ExecuteAsync(TimeSpan.FromSeconds(2), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
             }
         }
 
+        [TestMethod]
+        public void Use_Factory()
+        {
+            var factory = new MqttFactory();
+            using (var client = factory.CreateMqttClient())
+            {
+                var rpcClient = factory.CreateMqttRpcClient(client);
+
+                Assert.IsNotNull(rpcClient);
+            }
+        }
+
         async Task Execute_Success(MqttQualityOfServiceLevel qosLevel, MqttProtocolVersion protocolVersion)
         {
             using (var testEnvironment = CreateTestEnvironment())
@@ -151,57 +211,6 @@ namespace MQTTnet.Tests
             }
         }
 
-        [TestMethod]
-        public async Task Execute_Success_MQTT_V5_Mixed_Clients()
-        {
-            using (var testEnvironment = CreateTestEnvironment())
-            {
-                await testEnvironment.StartServer();
-                var responseSender = await testEnvironment.ConnectClient();
-                await responseSender.SubscribeAsync("MQTTnet.RPC/+/ping", MqttQualityOfServiceLevel.AtMostOnce);
-
-                responseSender.ApplicationMessageReceivedAsync += async e =>
-                {
-                    Assert.IsNull(e.ApplicationMessage.ResponseTopic);
-                    await responseSender.PublishStringAsync(e.ApplicationMessage.Topic + "/response", "pong");
-                };
-
-                var requestSender = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithProtocolVersion(MqttProtocolVersion.V500));
-
-                using (var rpcClient = new MqttRpcClient(requestSender, new MqttRpcClientOptionsBuilder().Build()))
-                {
-                    var response = await rpcClient.ExecuteAsync(TimeSpan.FromSeconds(5), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
-
-                    Assert.AreEqual("pong", Encoding.UTF8.GetString(response));
-                }
-            }
-        }
-
-        [TestMethod]
-        [ExpectedException(typeof(MqttCommunicationTimedOutException))]
-        public async Task Execute_Timeout_MQTT_V5_Mixed_Clients()
-        {
-            using (var testEnvironment = new TestEnvironment(TestContext))
-            {
-                await testEnvironment.StartServer();
-                var responseSender = await testEnvironment.ConnectClient();
-                await responseSender.SubscribeAsync("MQTTnet.RPC/+/ping", MqttQualityOfServiceLevel.AtMostOnce);
-
-                responseSender.ApplicationMessageReceivedAsync += async e =>
-                {
-                    Assert.IsNull(e.ApplicationMessage.ResponseTopic);
-                    await CompletedTask.Instance;
-                };
-
-                var requestSender = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithProtocolVersion(MqttProtocolVersion.V500));
-
-                using (var rpcClient = new MqttRpcClient(requestSender, new MqttRpcClientOptionsBuilder().Build()))
-                {
-                    var response = await rpcClient.ExecuteAsync(TimeSpan.FromSeconds(2), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
-                }
-            }
-        }
-
         class TestTopicStrategy : IMqttRpcClientTopicGenerationStrategy
         {
             public MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context)
@@ -214,4 +223,4 @@ namespace MQTTnet.Tests
             }
         }
     }
-}
+}

Source/MQTTnet.Tests/Extensions/WebSocket4Net_Tests.cs

@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Client;
+using MQTTnet.Exceptions;
+using MQTTnet.Extensions.WebSocket4Net;
+using MQTTnet.Tests.Helpers;
+
+namespace MQTTnet.Tests.Extensions
+{
+    [TestClass]
+    public sealed class WebSocket4Net_Tests
+    {
+        [TestMethod]
+        [ExpectedException(typeof(MqttCommunicationException))]
+        public async Task Connect_Failed_With_Invalid_Server()
+        {
+            var factory = new MqttFactory().UseWebSocket4Net();
+
+            using (var client = factory.CreateMqttClient())
+            {
+                var options = new MqttClientOptionsBuilder().WithWebSocketServer("ws://a.b/mqtt").WithTimeout(TimeSpan.FromSeconds(2)).Build();
+                await client.ConnectAsync(options).ConfigureAwait(false);
+            }
+        }
+
+        [TestMethod]
+        public void Use_Correct_Adapter()
+        {
+            // Should not throw exception
+            var factory = new MqttFactory().UseWebSocket4Net();
+            using (var client = factory.CreateMqttClient())
+            {
+                var adapterFactory = client.GetFieldValue("_adapterFactory");
+
+                Assert.IsInstanceOfType(adapterFactory, typeof(WebSocket4NetMqttClientAdapterFactory));
+            }
+        }
+
+        [TestMethod]
+        public void Use_WebSocket4Net()
+        {
+            // Should not throw exception
+            new MqttFactory().UseWebSocket4Net();
+        }
+    }
+}

Source/MQTTnet.Tests/Formatter/MqttBufferReader_Tests.cs

@@ -0,0 +1,310 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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 System.IO;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Exceptions;
+using MQTTnet.Formatter;
+
+namespace MQTTnet.Tests.Formatter
+{
+    [TestClass]
+    public sealed class MqttBufferReader_Tests
+    {
+        [TestMethod]
+        [ExpectedException(typeof(MqttProtocolViolationException), "Expected at least 4 bytes but there are only 3 bytes")]
+        public void Fire_Exception_If_Not_Enough_Data()
+        {
+            var buffer = new byte[] { 0, 1, 2 };
+
+            var reader = new MqttBufferReader();
+
+            reader.SetBuffer(buffer, 0, 3);
+
+            // 1 byte is missing.
+            reader.ReadFourByteInteger();
+        }
+
+        [TestMethod]
+        [ExpectedException(typeof(MqttProtocolViolationException), "Expected at least 4 bytes but there are only 3 bytes")]
+        public void Fire_Exception_If_Not_Enough_Data_With_Longer_Buffer()
+        {
+            var buffer = new byte[] { 0, 1, 2, 3, 4, 5, 6 };
+
+            var reader = new MqttBufferReader();
+
+            reader.SetBuffer(buffer, 0, 3);
+
+            // 1 byte is missing.
+            reader.ReadFourByteInteger();
+        }
+
+        [TestMethod]
+        public void Is_EndOfStream_Without_Buffer()
+        {
+            var reader = new MqttBufferReader();
+
+            Assert.IsTrue(reader.EndOfStream);
+            Assert.AreEqual(0, reader.BytesLeft);
+        }
+
+        [TestMethod]
+        public void Read_Remaining_Data_From_Larger_Buffer()
+        {
+            var buffer = new byte[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+
+            var reader = new MqttBufferReader();
+
+            // The used buffer contains more data than used!
+            reader.SetBuffer(buffer, 0, 5);
+
+            // This should only read 5 bytes even if more data is in the buffer
+            // due to custom bounds.
+            var remainingData = reader.ReadRemainingData();
+
+            Assert.IsTrue(reader.EndOfStream);
+            Assert.AreEqual(0, reader.BytesLeft);
+            Assert.AreEqual(5, remainingData.Length);
+        }
+
+        [TestMethod]
+        public void Read_Various_Positions_and_Offsets()
+        {
+            const int NumBufferElements = 1000;
+            const int NumTestSequences = 10000;
+
+            const string TestString = "The quick brown fox jumps over the lazy dog.";
+
+            var rndSeed = Environment.TickCount;
+            // rndSeed = ...; // assign random seed here if there is an error so that it can be repeated
+            var rnd = new Random(rndSeed);
+            // rndSeed is printed when an assert fails
+
+            var bufferElements = new List<ElementReference>();
+
+            byte[] elementBuffer;
+
+            // Fill a buffer with strings or numbers in big endian format
+            using (var ms = new MemoryStream())
+            {
+                using (var bw = new BinaryWriter(ms))
+                {
+                    var bufferOffset = 0;
+
+                    for (var i = 0; i < NumBufferElements; i++)
+                    {
+                        var nextElementType = (ElementReference.BufferElementType)rnd.Next(ElementReference.NumBufferElementTypes);
+
+                        byte[] elementBytes = null;
+                        uint elementNumberValue = 0; // all element number values fit into uint
+                        string elementStringValue = null;
+                        var elementSize = 0;
+
+                        var alreadyBigEndian = false;
+                        switch (nextElementType)
+                        {
+                            case ElementReference.BufferElementType.Byte:
+                                var byteValue = (byte)i;
+                                elementNumberValue = byteValue;
+                                elementSize = sizeof(byte);
+                                elementBytes = new byte[1] { byteValue };
+                                alreadyBigEndian = true; // nothing to swap
+                                break;
+                            case ElementReference.BufferElementType.TwoByteInt:
+                                var ushortValue = (ushort)i;
+                                elementNumberValue = ushortValue;
+                                elementSize = sizeof(ushort);
+                                elementBytes = BitConverter.GetBytes(ushortValue);
+                                break;
+                            case ElementReference.BufferElementType.FourByteInt:
+                                var uintValue = (uint)i;
+                                elementNumberValue = uintValue;
+                                elementSize = sizeof(uint);
+                                elementBytes = BitConverter.GetBytes(uintValue);
+                                break;
+                            case ElementReference.BufferElementType.VariableSizeInt:
+                            {
+                                elementNumberValue = (uint)i;
+                                var writer = new MqttBufferWriter(4, 4);
+                                writer.WriteVariableByteInteger(elementNumberValue);
+                                elementSize = writer.Length;
+                                elementBytes = new byte[elementSize];
+                                var buffer = writer.GetBuffer();
+                                Array.Copy(buffer, elementBytes, elementSize);
+                                alreadyBigEndian = true; // nothing to swap
+                            }
+                                break;
+                            case ElementReference.BufferElementType.String:
+                            {
+                                var stringLen = rnd.Next(TestString.Length);
+                                elementStringValue = TestString.Substring(0, stringLen); // could be empty
+                                var writer = new MqttBufferWriter(stringLen + 1, stringLen + 1);
+                                writer.WriteString(elementStringValue);
+                                elementSize = writer.Length;
+                                elementBytes = new byte[elementSize];
+                                var buffer = writer.GetBuffer();
+                                Array.Copy(buffer, elementBytes, elementSize);
+                                alreadyBigEndian = true; // nothing to swap
+                            }
+                                break;
+                        }
+
+                        if (BitConverter.IsLittleEndian && !alreadyBigEndian)
+                        {
+                            Array.Reverse(elementBytes);
+                        }
+
+                        bw.Write(elementBytes);
+                        bufferElements.Add(new ElementReference(nextElementType, elementSize, elementNumberValue, elementStringValue, bufferOffset));
+                        bufferOffset += elementSize;
+                    }
+
+                    elementBuffer = ms.ToArray();
+                }
+            }
+
+            for (var i = 0; i < NumTestSequences; i++)
+            {
+                var firstElementIndex = rnd.Next(NumBufferElements - 1);
+                // segmentElementIndex will be < NumBufferElements - 1, which means there is at least one byte left for segment element count
+                var elementCount = rnd.Next(NumBufferElements - firstElementIndex) + 1;
+                var lastElementIndex = firstElementIndex + elementCount - 1;
+                // Use element index to get buffer offsets
+                var lastElement = bufferElements[lastElementIndex];
+                var segmentStartPosition = bufferElements[firstElementIndex].BufferOffset;
+                var segmentEndPosition = lastElement.BufferOffset + lastElement.Size;
+                var segmentLength = segmentEndPosition - segmentStartPosition;
+
+                var reader = new MqttBufferReader();
+                reader.SetBuffer(elementBuffer, segmentStartPosition, segmentLength);
+
+                // read all elements in the buffer segment; values should be as expected              
+                for (var n = 0; n < elementCount; n++)
+                {
+                    var element = bufferElements[firstElementIndex + n];
+                    uint elementNumberValue = 0;
+                    string elementStringValue = null;
+
+                    var expectedPosition = element.BufferOffset - segmentStartPosition;
+                    Assert.AreEqual(expectedPosition, reader.Position);
+
+                    switch (element.Type)
+                    {
+                        case ElementReference.BufferElementType.Byte:
+                        {
+                            elementNumberValue = reader.ReadByte();
+                        }
+                            break;
+                        case ElementReference.BufferElementType.TwoByteInt:
+                        {
+                            elementNumberValue = reader.ReadTwoByteInteger();
+                        }
+                            break;
+                        case ElementReference.BufferElementType.FourByteInt:
+                        {
+                            elementNumberValue = reader.ReadFourByteInteger();
+                        }
+                            break;
+                        case ElementReference.BufferElementType.VariableSizeInt:
+                        {
+                            elementNumberValue = reader.ReadVariableByteInteger();
+                        }
+                            break;
+                        case ElementReference.BufferElementType.String:
+                        {
+                            elementStringValue = reader.ReadString();
+                        }
+                            break;
+                    }
+
+                    if (elementStringValue != null)
+                    {
+                        Assert.AreEqual(elementStringValue, element.StringValue, $"'{elementStringValue}' not equal '{element.StringValue}' with random seed {rndSeed}.");
+                    }
+                    else
+                    {
+                        Assert.AreEqual(elementNumberValue, element.NumberValue, $"{elementNumberValue} not equal {element.NumberValue} with random seed {rndSeed}.");
+                    }
+                }
+
+                // confirm end of stream
+                Assert.AreEqual(0, reader.BytesLeft, "BytesLeft not zero as expected with random seed " + rndSeed);
+                Assert.IsTrue(reader.EndOfStream, "Not end of stream as expected with random seed " + rndSeed);
+            }
+        }
+
+        [TestMethod]
+        public void Report_Correct_Length_For_Full_Buffer()
+        {
+            var buffer = new byte[] { 5, 6, 7, 8, 9 };
+
+            var reader = new MqttBufferReader();
+            reader.SetBuffer(buffer, 0, 5);
+
+            Assert.IsFalse(reader.EndOfStream);
+            Assert.AreEqual(5, reader.BytesLeft);
+        }
+
+        [TestMethod]
+        public void Report_Correct_Length_For_Partial_End_Buffer()
+        {
+            var buffer = new byte[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+
+            var reader = new MqttBufferReader();
+
+            // The used buffer contains more data than used!
+            reader.SetBuffer(buffer, 5, 5);
+
+            Assert.IsFalse(reader.EndOfStream);
+            Assert.AreEqual(5, reader.BytesLeft);
+        }
+
+        [TestMethod]
+        public void Report_Correct_Length_For_Partial_Start_Buffer()
+        {
+            var buffer = new byte[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+
+            var reader = new MqttBufferReader();
+
+            // The used buffer contains more data than used!
+            reader.SetBuffer(buffer, 0, 5);
+
+            Assert.IsFalse(reader.EndOfStream);
+            Assert.AreEqual(5, reader.BytesLeft);
+        }
+
+
+        // Helper class to build up a reference to elements of various types in a buffer
+        class ElementReference
+        {
+            public enum BufferElementType
+            {
+                Byte,
+                TwoByteInt,
+                FourByteInt,
+                VariableSizeInt,
+                String
+            }
+
+            public const int NumBufferElementTypes = 5;
+
+            public ElementReference(BufferElementType type, int size, uint numberValue, string stringValue, int bufferOffset)
+            {
+                Type = type;
+                Size = size;
+                NumberValue = numberValue;
+                StringValue = stringValue;
+                BufferOffset = bufferOffset;
+            }
+
+            public int BufferOffset { get; }
+            public uint NumberValue { get; }
+            public int Size { get; }
+            public string StringValue { get; }
+            public BufferElementType Type { get; }
+        }
+    }
+}

Source/MQTTnet.Tests/Formatter/MqttPacketSerialization_V3_Binary_Tests.cs

@@ -15,7 +15,7 @@ using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
-using MQTTnet.Tests.Extensions;
+using MQTTnet.Tests.Helpers;
 using MQTTnet.Tests.Mockups;
 
 namespace MQTTnet.Tests.Formatter

Source/MQTTnet.Tests/Helpers/MqttClientExtensions.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Client;
+using MQTTnet.Tests.Mockups;
+
+namespace MQTTnet.Tests.Helpers
+{
+    public static class MqttClientExtensions
+    {
+        public static TestApplicationMessageReceivedHandler TrackReceivedMessages(this IMqttClient client)
+        {
+            if (client == null)
+            {
+                throw new ArgumentNullException(nameof(client));
+            }
+
+            return new TestApplicationMessageReceivedHandler(client);
+        }
+    }
+}

Source/MQTTnet.Tests/Helpers/MqttPacketWriterExtensions.cs

@@ -5,7 +5,7 @@
 using MQTTnet.Formatter;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Tests.Extensions
+namespace MQTTnet.Tests.Helpers
 {
     public static class MqttPacketWriterExtensions
     {

Source/MQTTnet.Tests/Helpers/ReflectionExtensions.cs

@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Reflection;
+
+namespace MQTTnet.Tests.Helpers
+{
+    public static class ReflectionExtensions
+    {
+        public static object GetFieldValue(this object source, string fieldName)
+        {
+            if (source == null)
+            {
+                throw new ArgumentNullException(nameof(source));
+            }
+
+            var field = source.GetType().GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);
+            if (field == null)
+            {
+                throw new ArgumentException($"Field {fieldName} not found.");
+            }
+            
+            return field.GetValue(source);
+        }
+    }
+}

Source/MQTTnet.Tests/MQTTnet.Tests.csproj

@@ -7,21 +7,20 @@
         <EnableNETAnalyzers>false</EnableNETAnalyzers>
         <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
+        <NoWarn>1591;NETSDK1138</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
         <PackageReference Include="MSTest.TestAdapter" Version="2.2.10" />
         <PackageReference Include="MSTest.TestFramework" Version="2.2.10" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.2.0" />
-
-        <PackageReference Include="Microsoft.CodeAnalysis.Compilers" Version="4.0.1" />
-        <PackageReference Include="Microsoft.Net.Compilers" Version="4.0.1" />
     </ItemGroup>
 
     <ItemGroup>
         <ProjectReference Include="..\..\Source\MQTTnet.Extensions.ManagedClient\MQTTnet.Extensions.ManagedClient.csproj" />
         <ProjectReference Include="..\..\Source\MQTTnet.Extensions.Rpc\MQTTnet.Extensions.Rpc.csproj" />
         <ProjectReference Include="..\..\Source\MQTTnet\MQTTnet.csproj" />
+        <ProjectReference Include="..\MQTTnet.Extensions.WebSocket4Net\MQTTnet.Extensions.WebSocket4Net.csproj" />
     </ItemGroup>
 
 </Project>

Source/MQTTnet.Tests/MQTTv5/Server_Tests.cs

@@ -37,9 +37,9 @@ namespace MQTTnet.Tests.MQTTv5
                 await c1.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic("#").Build());
 
                 var c2 = await testEnvironment.ConnectClient(clientOptions);
-                c2.Dispose(); // Dispose will not send a DISCONNECT pattern first so the will message must be sent.
+                c2.Dispose(); // Dispose will not send a DISCONNECT packet first so the will message must be sent.
 
-                await Task.Delay(1000);
+                await LongTestDelay();
 
                 Assert.AreEqual(1, receivedMessagesCount);
             }

Source/MQTTnet.Tests/Mockups/TestApplicationMessageReceivedHandler.cs

@@ -27,6 +27,17 @@ namespace MQTTnet.Tests.Mockups
             mqttClient.ApplicationMessageReceivedAsync += OnApplicationMessageReceivedAsync;
         }
 
+        public int Count
+        {
+            get
+            {
+                lock (_receivedEventArgs)
+                {
+                    return _receivedEventArgs.Count;
+                }
+            }
+        }
+
         public List<MqttApplicationMessageReceivedEventArgs> ReceivedEventArgs
         {
             get

Source/MQTTnet.Tests/Protocol_Tests.cs

@@ -8,27 +8,48 @@ using MQTTnet.Formatter;
 namespace MQTTnet.Tests
 {
     [TestClass]
-    public class Protocol_Tests
+    public sealed class Protocol_Tests
     {
         [TestMethod]
         public void Encode_Four_Byte_Integer()
         {
             var writer = new MqttBufferWriter(4, 4);
-            
+
             for (uint value = 0; value < 268435455; value++)
             {
                 writer.WriteVariableByteInteger(value);
-                
+
                 var buffer = writer.GetBuffer();
-                
+
                 var reader = new MqttBufferReader();
                 reader.SetBuffer(buffer, 0, writer.Length);
                 var checkValue = reader.ReadVariableByteInteger();
 
                 Assert.AreEqual(value, checkValue);
-                
+
+                writer.Reset(0);
+            }
+        }
+
+        [TestMethod]
+        public void Encode_Two_Byte_Integer()
+        {
+            var writer = new MqttBufferWriter(2, 2);
+
+            for (ushort value = 0; value < ushort.MaxValue; value++)
+            {
+                writer.WriteTwoByteInteger(value);
+
+                var buffer = writer.GetBuffer();
+
+                var reader = new MqttBufferReader();
+                reader.SetBuffer(buffer, 0, writer.Length);
+                var checkValue = reader.ReadTwoByteInteger();
+
+                Assert.AreEqual(value, checkValue);
+
                 writer.Reset(0);
             }
         }
     }
-}
+}

Source/MQTTnet.Tests/Server/Injection_Tests.cs

@@ -1,6 +1,7 @@
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Client;
+using MQTTnet.Internal;
 using MQTTnet.Server;
 
 namespace MQTTnet.Tests.Server
@@ -60,5 +61,28 @@ namespace MQTTnet.Tests.Server
                 Assert.AreEqual("InjectedOne", messageReceivedHandler.ReceivedEventArgs[0].ApplicationMessage.Topic);
             }
         }
+
+        [TestMethod]
+        public async Task Intercept_Injected_Application_Message()
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                var server = await testEnvironment.StartServer();
+
+                MqttApplicationMessage interceptedMessage = null;
+                server.InterceptingPublishAsync += eventArgs =>
+                {
+                    interceptedMessage = eventArgs.ApplicationMessage;
+                    return CompletedTask.Instance;
+                };
+
+                var injectedApplicationMessage = new MqttApplicationMessageBuilder().WithTopic("InjectedOne").Build();
+                await server.InjectApplicationMessage(new InjectedMqttApplicationMessage(injectedApplicationMessage));
+
+                await LongTestDelay();
+
+                Assert.IsNotNull(interceptedMessage);
+            }
+        }
     }
 }

Source/MQTTnet.Tests/Server/MqttSubscriptionsManager_Tests.cs

@@ -114,6 +114,104 @@ namespace MQTTnet.Tests.Server
             Assert.AreEqual(result.QualityOfServiceLevel, MqttQualityOfServiceLevel.AtLeastOnce);
         }
 
+        [TestMethod]
+        public async Task MqttSubscriptionsManager_SubscribeWildcard1()
+        {
+            await SubscribeToTopic("house/+/room");
+            await SubscribeToTopic("house/+/room/+");
+
+            CheckIsSubscribed("house/1/room");
+            CheckIsSubscribed("house/1/room/bed");
+            CheckIsSubscribed("house/1/room/chair");
+            CheckIsSubscribed("house/2/room/bed");
+            CheckIsSubscribed("house/2/room/chair");
+
+            CheckIsNotSubscribed("house/1/room/bed/cover");
+            CheckIsNotSubscribed("house/1/study/bed");
+        }
+
+        [TestMethod]
+        public async Task MqttSubscriptionsManager_SubscribeWildcard2()
+        {
+            await SubscribeToTopic("house/+/room");
+            await SubscribeToTopic("house/+/room/#");
+
+            CheckIsSubscribed("house/1/room");
+            CheckIsSubscribed("house/1/room/bed");
+            CheckIsSubscribed("house/2/room");
+            CheckIsSubscribed("house/2/room/bed");
+            CheckIsSubscribed("house/2/room/bed/cover");
+
+            CheckIsNotSubscribed("house/1/level");
+            CheckIsNotSubscribed("house/1/level/door");
+        }
+
+        [TestMethod]
+        public async Task MqttSubscriptionsManager_SubscribeWildcard3()
+        {
+            await SubscribeToTopic("house/1/room");
+            await SubscribeToTopic("house/1/room/+");
+
+            CheckIsSubscribed("house/1/room");
+            CheckIsSubscribed("house/1/room/bed");
+            CheckIsSubscribed("house/1/room/chair");
+
+            CheckIsNotSubscribed("house/2/room");
+            CheckIsNotSubscribed("house/2/room/bed/cover");
+        }
+
+        [TestMethod]
+        public async Task MqttSubscriptionsManager_SubscribeWildcard4()
+        {
+            await SubscribeToTopic("house/1/+/+");
+
+            CheckIsSubscribed("house/1/room/bed");
+            CheckIsSubscribed("house/1/room/chair");
+
+            CheckIsNotSubscribed("house/1/room");
+            CheckIsNotSubscribed("house/1/room/bed/cover");
+        }
+
+        [TestMethod]
+        public async Task MqttSubscriptionsManager_SubscribeWildcard5()
+        {
+            await SubscribeToTopic("house/1/+/#");
+
+            CheckIsSubscribed("house/1/room/bed");
+            CheckIsSubscribed("house/1/room/chair");
+            CheckIsSubscribed("house/1/room/chair/leg");
+            CheckIsSubscribed("house/1/level/window");
+            CheckIsSubscribed("house/1/level/door");
+
+            CheckIsNotSubscribed("house/2/room/bed");
+        }
+
+        async Task SubscribeToTopic(string topic)
+        {
+            var sp = new MqttSubscribePacket
+            {
+                TopicFilters = new List<MqttTopicFilter>
+                {
+                    new MqttTopicFilter { Topic = topic, QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce },
+                }
+            };
+
+            await _subscriptionsManager.Subscribe(sp, CancellationToken.None);
+        }
+
+        void CheckIsSubscribed(string topic)
+        {
+            var result = CheckSubscriptions(topic, MqttQualityOfServiceLevel.AtMostOnce, "");
+            Assert.IsTrue(result.IsSubscribed);
+            Assert.AreEqual(result.QualityOfServiceLevel, MqttQualityOfServiceLevel.AtMostOnce);
+        }
+
+        void CheckIsNotSubscribed(string topic)
+        {
+            var result = CheckSubscriptions(topic, MqttQualityOfServiceLevel.AtMostOnce, "");
+            Assert.IsFalse(result.IsSubscribed);
+        }
+
         [TestInitialize]
         public void TestInitialize()
         {

Source/MQTTnet.Tests/Server/QoS_Tests.cs

@@ -26,6 +26,9 @@ namespace MQTTnet.Tests.Server
                 var dummyClient = await testEnvironment.ConnectClient(o => o.WithClientId("A").WithCleanSession(false));
                 await dummyClient.SubscribeAsync("#", MqttQualityOfServiceLevel.AtLeastOnce);
                 dummyClient.Dispose();
+
+                await LongTestDelay();
+                await LongTestDelay();
                 
                 // Now inject messages which are appended to the queue of the client.
                 await server.InjectApplicationMessage("T", "0", qualityOfServiceLevel: MqttQualityOfServiceLevel.AtLeastOnce);

Source/MQTTnet.Tests/Server/Session_Tests.cs

@@ -121,10 +121,9 @@ namespace MQTTnet.Tests.Server
                 Assert.AreEqual(true, session.Items["can_subscribe_x"]);
             }
         }
-
-        #if !NET452
         
         [TestMethod]
+        [DataRow(MqttProtocolVersion.V310)]
         [DataRow(MqttProtocolVersion.V311)]
         [DataRow(MqttProtocolVersion.V500)]
         public async Task Handle_Parallel_Connection_Attempts(MqttProtocolVersion protocolVersion)
@@ -150,8 +149,6 @@ namespace MQTTnet.Tests.Server
                 // Try to connect 50 clients at the same time.
                 var clients = await Task.WhenAll(Enumerable.Range(0, 50).Select(i => ConnectAndSubscribe(testEnvironment, options, OnReceive)));
 
-                await Task.Delay(TimeSpan.FromSeconds(10));
-                
                 var connectedClients = clients.Where(c => c?.TryPingAsync().GetAwaiter().GetResult() == true).ToList();
 
                 await LongTestDelay();
@@ -162,13 +159,12 @@ namespace MQTTnet.Tests.Server
                 var sendClient = await testEnvironment.ConnectClient(option2);
                 await sendClient.PublishStringAsync("aaa", "1");
 
-                await Task.Delay(TimeSpan.FromSeconds(5));
+                await LongTestDelay();
 
                 Assert.AreEqual(true, hasReceive);
             }
         }
-#endif
-        
+ 
         [DataTestMethod]
         [DataRow(MqttQualityOfServiceLevel.ExactlyOnce)]
         [DataRow(MqttQualityOfServiceLevel.AtLeastOnce)]

Source/MQTTnet.Tests/Server/Subscribe_Tests.cs

@@ -13,12 +13,56 @@ using MQTTnet.Internal;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 using MQTTnet.Server;
+using MQTTnet.Tests.Helpers;
 
 namespace MQTTnet.Tests.Server
 {
     [TestClass]
     public sealed class Subscribe_Tests : BaseTestClass
     {
+        [DataTestMethod]
+        [DataRow("A", "A", true)]
+        [DataRow("A", "B", false)]
+        [DataRow("A", "#", true)]
+        [DataRow("A", "+", true)]
+        [DataRow("A/B", "A/B", true)]
+        [DataRow("A/B", "A/+", true)]
+        [DataRow("A/B", "A/#", true)]
+        [DataRow("A/B/C", "A/B/C", true)]
+        [DataRow("A/B/C", "A/+/C", true)]
+        [DataRow("A/B/C", "A/+/+", true)]
+        [DataRow("A/B/C", "A/+/#", true)]
+        [DataRow("A/B/C/D", "A/B/C/D", true)]
+        [DataRow("A/B/C/D", "A/+/C/+", true)]
+        [DataRow("A/B/C/D", "A/+/C/#", true)]
+        [DataRow("A/B/C", "A/B/+", true)]
+        [DataRow("A/B1/B2/C", "A/+/C", false)]
+        public async Task Subscription_Roundtrip(string topic, string filter, bool shouldWork)
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                await testEnvironment.StartServer().ConfigureAwait(false);
+
+                var receiver = await testEnvironment.ConnectClient();
+                await receiver.SubscribeAsync(filter).ConfigureAwait(false);
+                var receivedMessages = receiver.TrackReceivedMessages();
+
+                var sender = await testEnvironment.ConnectClient();
+                await sender.PublishStringAsync(topic, "PAYLOAD").ConfigureAwait(false);
+
+                await LongTestDelay().ConfigureAwait(false);
+
+                if (shouldWork)
+                {
+                    Assert.AreEqual(1, receivedMessages.Count, message: "The filter should work!");
+                }
+                else
+                {
+                    Assert.AreEqual(0, receivedMessages.Count, message: "The filter should not work!");
+                }
+            }
+        }
+        
         [TestMethod]
         public async Task Deny_Invalid_Topic()
         {

Source/MQTTnet.Tests/Server/Will_Tests.cs

@@ -1,4 +1,3 @@
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Client;
@@ -10,33 +9,51 @@ namespace MQTTnet.Tests.Server
     [TestClass]
     public sealed class Will_Tests : BaseTestClass
     {
+        [TestMethod]
+        public async Task Intercept_Will_Message()
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                var server = await testEnvironment.StartServer().ConfigureAwait(false);
+
+                MqttApplicationMessage willMessage = null;
+                server.InterceptingPublishAsync += eventArgs =>
+                {
+                    willMessage = eventArgs.ApplicationMessage;
+                    return CompletedTask.Instance;
+                };
+
+                await testEnvironment.ConnectClient(new MqttClientOptionsBuilder()).ConfigureAwait(false);
+                var clientOptions = new MqttClientOptionsBuilder().WithWillTopic("My/last/will").WithWillQualityOfServiceLevel(MqttQualityOfServiceLevel.AtMostOnce);
+                var takeOverClient = await testEnvironment.ConnectClient(clientOptions).ConfigureAwait(false);
+                takeOverClient.Dispose(); // Dispose will not send a DISCONNECT pattern first so the will message must be sent.
+
+                await LongTestDelay().ConfigureAwait(false);
+
+                Assert.IsNotNull(willMessage);
+            }
+        }
+
         [TestMethod]
         public async Task Will_Message_Do_Not_Send_On_Clean_Disconnect()
         {
             using (var testEnvironment = CreateTestEnvironment())
             {
-                var receivedMessagesCount = 0;
-
                 await testEnvironment.StartServer();
 
+                var receiver = await testEnvironment.ConnectClient().ConfigureAwait(false);
+
+                var receivedMessages = testEnvironment.CreateApplicationMessageHandler(receiver);
+
+                await receiver.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic("#").Build());
+
                 var clientOptions = new MqttClientOptionsBuilder().WithWillTopic("My/last/will");
+                var sender = await testEnvironment.ConnectClient(clientOptions).ConfigureAwait(false);
+                await sender.DisconnectAsync().ConfigureAwait(false);
 
-                var c1 = await testEnvironment.ConnectClient();
+                await LongTestDelay().ConfigureAwait(false);
 
-                c1.ApplicationMessageReceivedAsync += e =>
-                {
-                    Interlocked.Increment(ref receivedMessagesCount);
-                    return CompletedTask.Instance;
-                };
-
-                await c1.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic("#").Build());
-
-                var c2 = await testEnvironment.ConnectClient(clientOptions);
-                await c2.DisconnectAsync().ConfigureAwait(false);
-
-                await Task.Delay(1000);
-
-                Assert.AreEqual(0, receivedMessagesCount);
+                Assert.AreEqual(0, receivedMessages.ReceivedEventArgs.Count);
             }
         }
 
@@ -47,24 +64,17 @@ namespace MQTTnet.Tests.Server
             {
                 await testEnvironment.StartServer();
 
-                var c1 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder());
-
-                var receivedMessagesCount = 0;
-                c1.ApplicationMessageReceivedAsync += e =>
-                {
-                    Interlocked.Increment(ref receivedMessagesCount);
-                    return CompletedTask.Instance;
-                };
-
-                await c1.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic("#").Build());
+                var receiver = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder()).ConfigureAwait(false);
+                var receivedMessages = testEnvironment.CreateApplicationMessageHandler(receiver);
+                await receiver.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic("#").Build());
 
                 var clientOptions = new MqttClientOptionsBuilder().WithWillTopic("My/last/will").WithWillQualityOfServiceLevel(MqttQualityOfServiceLevel.AtMostOnce);
-                var c2 = await testEnvironment.ConnectClient(clientOptions);
-                c2.Dispose(); // Dispose will not send a DISCONNECT pattern first so the will message must be sent.
+                var takeOverClient = await testEnvironment.ConnectClient(clientOptions).ConfigureAwait(false);
+                takeOverClient.Dispose(); // Dispose will not send a DISCONNECT pattern first so the will message must be sent.
 
-                await Task.Delay(1000);
+                await LongTestDelay().ConfigureAwait(false);
 
-                Assert.AreEqual(1, receivedMessagesCount);
+                Assert.AreEqual(1, receivedMessages.ReceivedEventArgs.Count);
             }
         }
     }

Source/MQTTnet/Client/MqttClient.cs

@@ -19,7 +19,6 @@ namespace MQTTnet.Client
     public sealed class MqttClient : Disposable, IMqttClient
     {
         readonly IMqttClientAdapterFactory _adapterFactory;
-        readonly MqttApplicationMessageFactory _applicationMessageFactory = new MqttApplicationMessageFactory();
         readonly AsyncEvent<MqttApplicationMessageReceivedEventArgs> _applicationMessageReceivedEvent = new AsyncEvent<MqttApplicationMessageReceivedEventArgs>();
 
         readonly MqttClientPublishResultFactory _clientPublishResultFactory = new MqttClientPublishResultFactory();
@@ -32,7 +31,6 @@ namespace MQTTnet.Client
         readonly object _disconnectLock = new object();
         readonly AsyncEvent<InspectMqttPacketEventArgs> _inspectPacketEvent = new AsyncEvent<InspectMqttPacketEventArgs>();
         readonly MqttNetSourceLogger _logger;
-        readonly MqttPacketFactories _packetFactories = new MqttPacketFactories();
 
         readonly MqttPacketIdentifierProvider _packetIdentifierProvider = new MqttPacketIdentifierProvider();
         readonly IMqttNetLogger _rootLogger;
@@ -207,7 +205,7 @@ namespace MQTTnet.Client
 
                 if (clientWasConnected)
                 {
-                    var disconnectPacket = _packetFactories.Disconnect.Create(options);
+                    var disconnectPacket = MqttPacketFactories.Disconnect.Create(options);
                     await SendAsync(disconnectPacket, cancellationToken).ConfigureAwait(false);
                 }
             }
@@ -241,7 +239,7 @@ namespace MQTTnet.Client
             ThrowIfDisposed();
             ThrowIfNotConnected();
 
-            var publishPacket = _packetFactories.Publish.Create(applicationMessage);
+            var publishPacket = MqttPacketFactories.Publish.Create(applicationMessage);
 
             switch (applicationMessage.QualityOfServiceLevel)
             {
@@ -301,7 +299,7 @@ namespace MQTTnet.Client
             ThrowIfDisposed();
             ThrowIfNotConnected();
 
-            var subscribePacket = _packetFactories.Subscribe.Create(options);
+            var subscribePacket = MqttPacketFactories.Subscribe.Create(options);
             subscribePacket.PacketIdentifier = _packetIdentifierProvider.GetNextPacketIdentifier();
 
             var subAckPacket = await SendAndReceiveAsync<MqttSubAckPacket>(subscribePacket, cancellationToken).ConfigureAwait(false);
@@ -319,7 +317,7 @@ namespace MQTTnet.Client
             ThrowIfDisposed();
             ThrowIfNotConnected();
 
-            var unsubscribePacket = _packetFactories.Unsubscribe.Create(options);
+            var unsubscribePacket = MqttPacketFactories.Unsubscribe.Create(options);
             unsubscribePacket.PacketIdentifier = _packetIdentifierProvider.GetNextPacketIdentifier();
 
             var unsubAckPacket = await SendAndReceiveAsync<MqttUnsubAckPacket>(unsubscribePacket, cancellationToken).ConfigureAwait(false);
@@ -347,7 +345,7 @@ namespace MQTTnet.Client
             {
                 if (!eventArgs.ProcessingFailed)
                 {
-                    var pubAckPacket = _packetFactories.PubAck.Create(eventArgs);
+                    var pubAckPacket = MqttPacketFactories.PubAck.Create(eventArgs);
                     return SendAsync(pubAckPacket, cancellationToken);
                 }
             }
@@ -355,7 +353,7 @@ namespace MQTTnet.Client
             {
                 if (!eventArgs.ProcessingFailed)
                 {
-                    var pubRecPacket = _packetFactories.PubRec.Create(eventArgs);
+                    var pubRecPacket = MqttPacketFactories.PubRec.Create(eventArgs);
                     return SendAsync(pubRecPacket, cancellationToken);
                 }
             }
@@ -373,7 +371,7 @@ namespace MQTTnet.Client
 
             try
             {
-                var connectPacket = _packetFactories.Connect.Create(options);
+                var connectPacket = MqttPacketFactories.Connect.Create(options);
 
                 var connAckPacket = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket, cancellationToken).ConfigureAwait(false);
 
@@ -535,7 +533,7 @@ namespace MQTTnet.Client
 
         async Task<MqttApplicationMessageReceivedEventArgs> HandleReceivedApplicationMessageAsync(MqttPublishPacket publishPacket)
         {
-            var applicationMessage = _applicationMessageFactory.Create(publishPacket);
+            var applicationMessage = MqttApplicationMessageFactory.Create(publishPacket);
             var eventArgs = new MqttApplicationMessageReceivedEventArgs(Options.ClientId, applicationMessage, publishPacket, AcknowledgeReceivedPublishPacket);
 
             await _applicationMessageReceivedEvent.InvokeAsync(eventArgs).ConfigureAwait(false);
@@ -601,7 +599,7 @@ namespace MQTTnet.Client
             {
                 // The packet is unknown. Probably due to a restart of the client.
                 // So wen send this to the server to trigger a full resend of the message.
-                var pubRelPacket = _packetFactories.PubRel.Create(pubRecPacket, MqttApplicationMessageReceivedReasonCode.PacketIdentifierNotFound);
+                var pubRelPacket = MqttPacketFactories.PubRel.Create(pubRecPacket, MqttApplicationMessageReceivedReasonCode.PacketIdentifierNotFound);
                 return SendAsync(pubRelPacket, cancellationToken);
             }
 
@@ -610,7 +608,7 @@ namespace MQTTnet.Client
 
         Task ProcessReceivedPubRelPacket(MqttPubRelPacket pubRelPacket, CancellationToken cancellationToken)
         {
-            var pubCompPacket = _packetFactories.PubComp.Create(pubRelPacket, MqttApplicationMessageReceivedReasonCode.Success);
+            var pubCompPacket = MqttPacketFactories.PubComp.Create(pubRelPacket, MqttApplicationMessageReceivedReasonCode.Success);
             return SendAsync(pubCompPacket, cancellationToken);
         }
 
@@ -637,7 +635,7 @@ namespace MQTTnet.Client
 
             var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket, cancellationToken).ConfigureAwait(false);
 
-            var pubRelPacket = _packetFactories.PubRel.Create(pubRecPacket, MqttApplicationMessageReceivedReasonCode.Success);
+            var pubRelPacket = MqttPacketFactories.PubRel.Create(pubRecPacket, MqttApplicationMessageReceivedReasonCode.Success);
 
             var pubCompPacket = await SendAndReceiveAsync<MqttPubCompPacket>(pubRelPacket, cancellationToken).ConfigureAwait(false);
 

Source/MQTTnet/Diagnostics/Logger/MqttNetSourceLoggerExtensions.cs

@@ -6,17 +6,100 @@ using System;
 
 namespace MQTTnet.Diagnostics
 {
+    /*
+     * The logger uses generic parameters in order to avoid boxing of parameter values like integers etc.
+     */
+    
     public static class MqttNetSourceLoggerExtensions
     {
-        /*
-         * The logger uses generic parameters in order to avoid boxing of parameter values like integers etc.
-         */
-
-        public static MqttNetSourceLogger WithSource(this IMqttNetLogger logger, string source)
+        public static void Error<TParameter1>(this MqttNetSourceLogger logger, Exception exception, string message, TParameter1 parameter1)
         {
-            if (logger == null) throw new ArgumentNullException(nameof(logger));
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
 
-            return new MqttNetSourceLogger(logger, source);
+            logger.Publish(MqttNetLogLevel.Error, message, new object[] { parameter1 }, exception);
+        }
+
+        public static void Error<TParameter1, TParameter2>(this MqttNetSourceLogger logger, Exception exception, string message, TParameter1 parameter1, TParameter2 parameter2)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(MqttNetLogLevel.Error, message, new object[] { parameter1, parameter2 }, exception);
+        }
+
+        public static void Error(this MqttNetSourceLogger logger, Exception exception, string message)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(MqttNetLogLevel.Error, message, null, exception);
+        }
+
+        public static void Error(this MqttNetSourceLogger logger, string message)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(MqttNetLogLevel.Error, message, null, null);
+        }
+
+        public static void Info<TParameter1>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(MqttNetLogLevel.Info, message, new object[] { parameter1 }, null);
+        }
+
+        public static void Info<TParameter1, TParameter2>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1, TParameter2 parameter2)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(MqttNetLogLevel.Info, message, new object[] { parameter1, parameter2 }, null);
+        }
+
+        public static void Info(this MqttNetSourceLogger logger, string message)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(MqttNetLogLevel.Info, message, null, null);
+        }
+
+        public static void Publish<TParameter1>(this MqttNetSourceLogger logger, MqttNetLogLevel logLevel, Exception exception, string message, TParameter1 parameter1)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(logLevel, message, new object[] { parameter1 }, exception);
+        }
+        
+        public static void Publish<TParameter1, TParameter2>(this MqttNetSourceLogger logger, MqttNetLogLevel logLevel, Exception exception, string message, TParameter1 parameter1, TParameter2 parameter2)
+        {
+            if (!logger.IsEnabled)
+            {
+                return;
+            }
+
+            logger.Publish(logLevel, message, new object[] { parameter1, parameter2 }, exception);
         }
 
         public static void Verbose<TParameter1>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1)
@@ -26,7 +109,7 @@ namespace MQTTnet.Diagnostics
                 return;
             }
 
-            logger.Publish(MqttNetLogLevel.Verbose, message, new object[] {parameter1}, null);
+            logger.Publish(MqttNetLogLevel.Verbose, message, new object[] { parameter1 }, null);
         }
 
         public static void Verbose<TParameter1, TParameter2>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1, TParameter2 parameter2)
@@ -36,10 +119,14 @@ namespace MQTTnet.Diagnostics
                 return;
             }
 
-            logger.Publish(MqttNetLogLevel.Verbose, message, new object[] {parameter1, parameter2}, null);
+            logger.Publish(MqttNetLogLevel.Verbose, message, new object[] { parameter1, parameter2 }, null);
         }
 
-        public static void Verbose<TParameter1, TParameter2, TParameter3>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1, TParameter2 parameter2,
+        public static void Verbose<TParameter1, TParameter2, TParameter3>(
+            this MqttNetSourceLogger logger,
+            string message,
+            TParameter1 parameter1,
+            TParameter2 parameter2,
             TParameter3 parameter3)
         {
             if (!logger.IsEnabled)
@@ -47,7 +134,7 @@ namespace MQTTnet.Diagnostics
                 return;
             }
 
-            logger.Publish(MqttNetLogLevel.Verbose, message, new object[] {parameter1, parameter2, parameter3}, null);
+            logger.Publish(MqttNetLogLevel.Verbose, message, new object[] { parameter1, parameter2, parameter3 }, null);
         }
 
         public static void Verbose(this MqttNetSourceLogger logger, string message)
@@ -60,134 +147,74 @@ namespace MQTTnet.Diagnostics
             logger.Publish(MqttNetLogLevel.Verbose, message, null, null);
         }
 
-        public static void Info<TParameter1>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1)
-        {
-            if (!logger.IsEnabled)
-            {
-                return;
-            }
-
-            logger.Publish(MqttNetLogLevel.Info, message, new object[] {parameter1}, null);
-        }
-        
-        public static void Info<TParameter1, TParameter2>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1, TParameter2 parameter2)
-        {
-            if (!logger.IsEnabled)
-            {
-                return;
-            }
-
-            logger.Publish(MqttNetLogLevel.Info, message, new object[] {parameter1, parameter2}, null);
-        }
-
-        public static void Info(this MqttNetSourceLogger logger, string message)
-        {
-            if (!logger.IsEnabled)
-            {
-                return;
-            }
-            
-            logger.Publish(MqttNetLogLevel.Info, message, null, null);
-        }
-
         public static void Warning<TParameter1>(this MqttNetSourceLogger logger, Exception exception, string message, TParameter1 parameter1)
         {
             if (!logger.IsEnabled)
             {
                 return;
             }
-            
-            logger.Publish(MqttNetLogLevel.Warning, message, new object[] {parameter1}, exception);
+
+            logger.Publish(MqttNetLogLevel.Warning, message, new object[] { parameter1 }, exception);
         }
-        
+
         public static void Warning<TParameter1, TParameter2>(this MqttNetSourceLogger logger, Exception exception, string message, TParameter1 parameter1, TParameter2 parameter2)
         {
             if (!logger.IsEnabled)
             {
                 return;
             }
-            
-            logger.Publish(MqttNetLogLevel.Warning, message, new object[] {parameter1, parameter2}, exception);
+
+            logger.Publish(MqttNetLogLevel.Warning, message, new object[] { parameter1, parameter2 }, exception);
         }
-        
+
         public static void Warning(this MqttNetSourceLogger logger, Exception exception, string message)
         {
             if (!logger.IsEnabled)
             {
                 return;
             }
-            
+
             logger.Publish(MqttNetLogLevel.Warning, message, null, exception);
         }
-        
+
         public static void Warning<TParameter1>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1)
         {
             if (!logger.IsEnabled)
             {
                 return;
             }
-            
-            logger.Publish(MqttNetLogLevel.Warning, message, new object[] {parameter1}, null);
+
+            logger.Publish(MqttNetLogLevel.Warning, message, new object[] { parameter1 }, null);
         }
-        
+
         public static void Warning<TParameter1, TParameter2>(this MqttNetSourceLogger logger, string message, TParameter1 parameter1, TParameter2 parameter2)
         {
             if (!logger.IsEnabled)
             {
                 return;
             }
-            
-            logger.Publish(MqttNetLogLevel.Warning, message, new object[] {parameter1, parameter2}, null);
+
+            logger.Publish(MqttNetLogLevel.Warning, message, new object[] { parameter1, parameter2 }, null);
         }
-        
+
         public static void Warning(this MqttNetSourceLogger logger, string message)
         {
             if (!logger.IsEnabled)
             {
                 return;
             }
-            
+
             logger.Publish(MqttNetLogLevel.Warning, message, null, null);
         }
 
-        public static void Error<TParameter1>(this MqttNetSourceLogger logger, Exception exception, string message, TParameter1 parameter1)
+        public static MqttNetSourceLogger WithSource(this IMqttNetLogger logger, string source)
         {
-            if (!logger.IsEnabled)
+            if (logger == null)
             {
-                return;
+                throw new ArgumentNullException(nameof(logger));
             }
-            
-            logger.Publish(MqttNetLogLevel.Error, message, new object[] {parameter1}, exception);
-        }
-        
-        public static void Error<TParameter1, TParameter2>(this MqttNetSourceLogger logger, Exception exception, string message, TParameter1 parameter1, TParameter2 parameter2)
-        {
-            if (!logger.IsEnabled)
-            {
-                return;
-            }
-            
-            logger.Publish(MqttNetLogLevel.Error, message, new object[] {parameter1, parameter2}, exception);
-        }
 
-        public static void Error(this MqttNetSourceLogger logger, Exception exception, string message)
-        {
-            if (!logger.IsEnabled)
-            {
-                return;
-            }
-            
-            logger.Publish(MqttNetLogLevel.Error, message, null, exception);
-        }
-
-        public static void Error(this MqttNetSourceLogger logger, string message)
-        {
-            if (!logger.IsEnabled)
-            {
-                return;
-            }
-            
-            logger.Publish(MqttNetLogLevel.Error, message, null, null);
+            return new MqttNetSourceLogger(logger, source);
         }
     }
 }

Source/MQTTnet/Formatter/MqttApplicationMessageFactory.cs

@@ -7,9 +7,9 @@ using MQTTnet.Packets;
 
 namespace MQTTnet.Formatter
 {
-    public sealed class MqttApplicationMessageFactory
+    public static class MqttApplicationMessageFactory
     {
-        public MqttApplicationMessage Create(MqttPublishPacket publishPacket)
+        public static MqttApplicationMessage Create(MqttPublishPacket publishPacket)
         {
             if (publishPacket == null)
             {

Source/MQTTnet/Formatter/MqttBufferReader.cs

@@ -7,21 +7,24 @@ using System.Runtime.CompilerServices;
 using System.Text;
 using MQTTnet.Exceptions;
 using MQTTnet.Internal;
+#if NETCOREAPP3_0_OR_GREATER
+using System.Buffers.Binary;
+#endif
 
 namespace MQTTnet.Formatter
 {
     public sealed class MqttBufferReader
     {
         byte[] _buffer = EmptyBuffer.Array;
-        int _initialPosition;
-        int _length;
+        int _maxPosition;
+        int _offset;
         int _position;
 
-        public bool EndOfStream => _position == _length;
-        
-        public int Position => _position;
-        
-        public int BytesLeft => _length - _position;
+        public int BytesLeft => _maxPosition - _position;
+
+        public bool EndOfStream => BytesLeft == 0;
+
+        public int Position => _position - _offset;
 
         public byte[] ReadBinaryData()
         {
@@ -35,7 +38,7 @@ namespace MQTTnet.Formatter
             ValidateReceiveBuffer(length);
 
             var result = new byte[length];
-            Array.Copy(_buffer, _position, result, 0, length);
+            MqttMemoryHelper.Copy(_buffer, _position, result, 0, length);
             _position += length;
 
             return result;
@@ -44,7 +47,6 @@ namespace MQTTnet.Formatter
         public byte ReadByte()
         {
             ValidateReceiveBuffer(1);
-
             return _buffer[_position++];
         }
 
@@ -52,25 +54,32 @@ namespace MQTTnet.Formatter
         {
             ValidateReceiveBuffer(4);
 
-            var byte0 = _buffer[_position++];
-            var byte1 = _buffer[_position++];
-            var byte2 = _buffer[_position++];
-            var byte3 = _buffer[_position++];
+#if NETCOREAPP3_0_OR_GREATER
+            var value = BinaryPrimitives.ReadUInt32BigEndian(_buffer.AsSpan(_position));
+#else
+            var byte0 = _buffer[_position];
+            var byte1 = _buffer[_position + 1];
+            var byte2 = _buffer[_position + 2];
+            var byte3 = _buffer[_position + 3];
 
-            return (uint)((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
+            var value = (uint)((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
+#endif
+
+            _position += 4;
+            return value;
         }
 
         public byte[] ReadRemainingData()
         {
-            var bufferLength = _length - _position;
-
+            var bufferLength = BytesLeft;
             if (bufferLength == 0)
             {
                 return EmptyBuffer.Array;
             }
-            
+
             var buffer = new byte[bufferLength];
-            Array.Copy(_buffer, _position, buffer, 0, bufferLength);
+            MqttMemoryHelper.Copy(_buffer, _position, buffer, 0, bufferLength);
+            _position += bufferLength;
 
             return buffer;
         }
@@ -83,10 +92,16 @@ namespace MQTTnet.Formatter
             {
                 return string.Empty;
             }
-            
+
             ValidateReceiveBuffer(length);
 
+#if NETCOREAPP3_0_OR_GREATER
+            // AsSpan() version is slightly faster. Not much but at least a little bit.
+            var result = Encoding.UTF8.GetString(_buffer.AsSpan(_position, length));
+#else
             var result = Encoding.UTF8.GetString(_buffer, _position, length);
+#endif
+
             _position += length;
             return result;
         }
@@ -95,10 +110,17 @@ namespace MQTTnet.Formatter
         {
             ValidateReceiveBuffer(2);
 
-            var msb = _buffer[_position++];
-            var lsb = _buffer[_position++];
+#if NETCOREAPP3_0_OR_GREATER
+            var value = BinaryPrimitives.ReadUInt16BigEndian(_buffer.AsSpan(_position));
+#else
+            var msb = _buffer[_position];
+            var lsb = _buffer[_position + 1];
 
-            return (ushort)((msb << 8) | lsb);
+            var value = (ushort)((msb << 8) | lsb);
+#endif
+
+            _position += 2;
+            return value;
         }
 
         public uint ReadVariableByteInteger()
@@ -125,23 +147,29 @@ namespace MQTTnet.Formatter
 
         public void Seek(int position)
         {
-            _position = _initialPosition + position;
+            _position = _offset + position;
         }
 
-        public void SetBuffer(byte[] buffer, int position, int length)
+        public void SetBuffer(ArraySegment<byte> buffer)
         {
-            _buffer = buffer;
-            _initialPosition = position;
-            _position = position;
-            _length = length;
+            SetBuffer(buffer.Array, buffer.Offset, buffer.Count);
+        }
+
+        public void SetBuffer(byte[] buffer, int offset, int length)
+        {
+            _buffer = buffer ?? throw new ArgumentNullException(nameof(buffer));
+            _offset = offset;
+            _position = offset;
+            _maxPosition = offset + length;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         void ValidateReceiveBuffer(int length)
         {
-            if (_length < _position + length)
+            var newPosition = _position + length;
+            if (_maxPosition < newPosition)
             {
-                throw new MqttProtocolViolationException($"Expected at least {Position + length} bytes but there are only {_length} bytes");
+                throw new MqttProtocolViolationException($"Expected at least {newPosition} bytes but there are only {_maxPosition} bytes");
             }
         }
     }

Source/MQTTnet/Formatter/MqttBufferWriter.cs

@@ -6,6 +6,7 @@ using System;
 using System.Runtime.CompilerServices;
 using System.Text;
 using MQTTnet.Exceptions;
+using MQTTnet.Internal;
 using MQTTnet.Protocol;
 
 namespace MQTTnet.Formatter
@@ -63,17 +64,30 @@ namespace MQTTnet.Formatter
             return _buffer;
         }
 
-        public static int GetLengthOfVariableInteger(uint value)
+        public static int GetVariableByteIntegerSize(uint value)
         {
-            var result = 0;
-            var x = value;
-            do
-            {
-                x /= 128;
-                result++;
-            } while (x > 0);
+            // From RFC: Table 2.4 Size of Remaining Length field
 
-            return result;
+            // 0 (0x00) to 127 (0x7F)
+            if (value <= 127)
+            {
+                return 1;
+            }
+
+            // 128 (0x80, 0x01) to 16 383 (0xFF, 0x7F)
+            if (value <= 16383)
+            {
+                return 2;
+            }
+
+            // 16 384 (0x80, 0x80, 0x01) to 2 097 151 (0xFF, 0xFF, 0x7F)
+            if (value <= 2097151)
+            {
+                return 3;
+            }
+
+            // 2 097 152 (0x80, 0x80, 0x80, 0x01) to 268 435 455 (0xFF, 0xFF, 0xFF, 0x7F)
+            return 4;
         }
 
         public void Reset(int length)
@@ -90,18 +104,12 @@ namespace MQTTnet.Formatter
 
         public void Write(MqttBufferWriter propertyWriter)
         {
-            if (propertyWriter is MqttBufferWriter writer)
-            {
-                WriteBinary(writer._buffer, 0, writer.Length);
-                return;
-            }
-
             if (propertyWriter == null)
             {
                 throw new ArgumentNullException(nameof(propertyWriter));
             }
 
-            throw new InvalidOperationException($"{nameof(propertyWriter)} must be of type {nameof(MqttBufferWriter)}");
+            WriteBinary(propertyWriter._buffer, 0, propertyWriter.Length);
         }
 
         public void WriteBinary(byte[] buffer, int offset, int count)
@@ -118,7 +126,7 @@ namespace MQTTnet.Formatter
 
             EnsureAdditionalCapacity(count);
 
-            Array.Copy(buffer, offset, _buffer, _position, count);
+            MqttMemoryHelper.Copy(buffer, offset, _buffer, _position, count);
             IncreasePosition(count);
         }
 
@@ -142,7 +150,7 @@ namespace MQTTnet.Formatter
                 _buffer[_position] = (byte)(valueLength >> 8);
                 _buffer[_position + 1] = (byte)valueLength;
 
-                Array.Copy(value, 0, _buffer, _position + 2, valueLength);
+                MqttMemoryHelper.Copy(value, 0, _buffer, _position + 2, valueLength);
                 IncreasePosition(valueLength + 2);
             }
         }
@@ -180,7 +188,7 @@ namespace MQTTnet.Formatter
 
                 _buffer[_position] = (byte)(writtenBytes >> 8);
                 _buffer[_position + 1] = (byte)writtenBytes;
-                
+
                 IncreasePosition(writtenBytes + 2);
             }
         }

Source/MQTTnet/Formatter/MqttPacketBuffer.cs

@@ -37,28 +37,28 @@ namespace MQTTnet.Formatter
 
         public byte[] ToArray()
         {
-            if (Packet.Count == 0)
+            if (Payload.Count == 0)
             {
                 return Packet.ToArray();
             }
 
             var buffer = new byte[Length];
-            Array.Copy(Packet.Array, Packet.Offset, buffer, 0, Packet.Count);
-            Array.Copy(Payload.Array, Payload.Offset, buffer, Packet.Count, Payload.Count);
+            MqttMemoryHelper.Copy(Packet.Array, Packet.Offset, buffer, 0, Packet.Count);
+            MqttMemoryHelper.Copy(Payload.Array, Payload.Offset, buffer, Packet.Count, Payload.Count);
 
             return buffer;
         }
         
         public ArraySegment<byte> Join()
         {
-            if (Packet.Count == 0)
+            if (Payload.Count == 0)
             {
                 return Packet;
             }
 
             var buffer = new byte[Length];
-            Array.Copy(Packet.Array, Packet.Offset, buffer, 0, Packet.Count);
-            Array.Copy(Payload.Array, Payload.Offset, buffer, Packet.Count, Payload.Count);
+            MqttMemoryHelper.Copy(Packet.Array, Packet.Offset, buffer, 0, Packet.Count);
+            MqttMemoryHelper.Copy(Payload.Array, Payload.Offset, buffer, Packet.Count, Payload.Count);
 
             return new ArraySegment<byte>(buffer);
         }

Source/MQTTnet/Formatter/MqttPacketFactories.cs

@@ -4,30 +4,30 @@
 
 namespace MQTTnet.Formatter
 {
-    public sealed class MqttPacketFactories
+    public static class MqttPacketFactories
     {
-        public MqttConnAckPacketFactory ConnAck { get; } = new MqttConnAckPacketFactory();
+        public static MqttConnAckPacketFactory ConnAck { get; } = new MqttConnAckPacketFactory();
         
-        public MqttConnectPacketFactory Connect { get; } = new MqttConnectPacketFactory();
+        public static MqttConnectPacketFactory Connect { get; } = new MqttConnectPacketFactory();
 
-        public MqttDisconnectPacketFactory Disconnect { get; } = new MqttDisconnectPacketFactory();
+        public static MqttDisconnectPacketFactory Disconnect { get; } = new MqttDisconnectPacketFactory();
 
-        public MqttPubAckPacketFactory PubAck { get; } = new MqttPubAckPacketFactory();
+        public static MqttPubAckPacketFactory PubAck { get; } = new MqttPubAckPacketFactory();
 
-        public MqttPubCompPacketFactory PubComp { get; } = new MqttPubCompPacketFactory();
+        public static MqttPubCompPacketFactory PubComp { get; } = new MqttPubCompPacketFactory();
 
-        public MqttPublishPacketFactory Publish { get; } = new MqttPublishPacketFactory();
+        public static MqttPublishPacketFactory Publish { get; } = new MqttPublishPacketFactory();
 
-        public MqttPubRecPacketFactory PubRec { get; } = new MqttPubRecPacketFactory();
+        public static MqttPubRecPacketFactory PubRec { get; } = new MqttPubRecPacketFactory();
 
-        public MqttPubRelPacketFactory PubRel { get; } = new MqttPubRelPacketFactory();
+        public static MqttPubRelPacketFactory PubRel { get; } = new MqttPubRelPacketFactory();
 
-        public MqttSubAckPacketFactory SubAck { get; } = new MqttSubAckPacketFactory();
+        public static MqttSubAckPacketFactory SubAck { get; } = new MqttSubAckPacketFactory();
 
-        public MqttSubscribePacketFactory Subscribe { get; } = new MqttSubscribePacketFactory();
+        public static MqttSubscribePacketFactory Subscribe { get; } = new MqttSubscribePacketFactory();
 
-        public MqttUnsubAckPacketFactory UnsubAck { get; } = new MqttUnsubAckPacketFactory();
+        public static MqttUnsubAckPacketFactory UnsubAck { get; } = new MqttUnsubAckPacketFactory();
 
-        public MqttUnsubscribePacketFactory Unsubscribe { get; } = new MqttUnsubscribePacketFactory();
+        public static MqttUnsubscribePacketFactory Unsubscribe { get; } = new MqttUnsubscribePacketFactory();
     }
 }

Source/MQTTnet/Formatter/MqttPubAckPacketFactory.cs

@@ -14,7 +14,6 @@ namespace MQTTnet.Formatter
     {
         public MqttPubAckPacket Create(
             MqttPublishPacket publishPacket,
-            InterceptingPublishEventArgs interceptingPublishEventArgs,
             DispatchApplicationMessageResult dispatchApplicationMessageResult)
         {
             if (publishPacket == null)
@@ -22,28 +21,19 @@ namespace MQTTnet.Formatter
                 throw new ArgumentNullException(nameof(publishPacket));
             }
 
+            if (dispatchApplicationMessageResult == null)
+            {
+                throw new ArgumentNullException(nameof(dispatchApplicationMessageResult));
+            }
+
             var pubAckPacket = new MqttPubAckPacket
             {
-                PacketIdentifier = publishPacket.PacketIdentifier
+                PacketIdentifier = publishPacket.PacketIdentifier,
+                ReasonCode = (MqttPubAckReasonCode)dispatchApplicationMessageResult.ReasonCode,
+                ReasonString = dispatchApplicationMessageResult.ReasonString,
+                UserProperties = dispatchApplicationMessageResult.UserProperties
             };
-
-            if (dispatchApplicationMessageResult.MatchingSubscribersCount == 0)
-            {
-                // NoMatchingSubscribers is ONLY sent by the server!
-                pubAckPacket.ReasonCode = MqttPubAckReasonCode.NoMatchingSubscribers;
-            }
-            else
-            {
-                pubAckPacket.ReasonCode = MqttPubAckReasonCode.Success;
-            }
-
-            if (interceptingPublishEventArgs != null)
-            {
-                pubAckPacket.ReasonCode = (MqttPubAckReasonCode)(int)interceptingPublishEventArgs.Response.ReasonCode;
-                pubAckPacket.ReasonString = interceptingPublishEventArgs.Response.ReasonString;
-                pubAckPacket.UserProperties = interceptingPublishEventArgs.Response.UserProperties;
-            }
-
+            
             return pubAckPacket;
         }
 

Source/MQTTnet/Formatter/MqttPubRecPacketFactory.cs

@@ -25,10 +25,7 @@ namespace MQTTnet.Formatter
             return pubRecPacket;
         }
 
-        public MqttPacket Create(
-            MqttPublishPacket publishPacket,
-            InterceptingPublishEventArgs interceptingPublishEventArgs,
-            DispatchApplicationMessageResult dispatchApplicationMessageResult)
+        public MqttPacket Create(MqttPublishPacket publishPacket, DispatchApplicationMessageResult dispatchApplicationMessageResult)
         {
             if (publishPacket == null)
             {
@@ -38,21 +35,11 @@ namespace MQTTnet.Formatter
             var pubRecPacket = new MqttPubRecPacket
             {
                 PacketIdentifier = publishPacket.PacketIdentifier,
-                ReasonCode = MqttPubRecReasonCode.Success
+                ReasonCode = (MqttPubRecReasonCode)dispatchApplicationMessageResult.ReasonCode,
+                ReasonString = dispatchApplicationMessageResult.ReasonString,
+                UserProperties = dispatchApplicationMessageResult.UserProperties
             };
 
-            if (dispatchApplicationMessageResult.MatchingSubscribersCount == 0)
-            {
-                pubRecPacket.ReasonCode = MqttPubRecReasonCode.NoMatchingSubscribers;
-            }
-
-            if (interceptingPublishEventArgs != null)
-            {
-                pubRecPacket.ReasonCode = (MqttPubRecReasonCode)(int)interceptingPublishEventArgs.Response.ReasonCode;
-                pubRecPacket.ReasonString = interceptingPublishEventArgs.Response.ReasonString;
-                pubRecPacket.UserProperties = interceptingPublishEventArgs.Response.UserProperties;
-            }
-
             return pubRecPacket;
         }
 

Source/MQTTnet/Formatter/V3/MqttV3PacketFormatter.cs

@@ -78,7 +78,7 @@ namespace MQTTnet.Formatter.V3
                     return DecodeSubscribePacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.SubAck:
                     return DecodeSubAckPacket(receivedMqttPacket.Body);
-                case MqttControlPacketType.Unsubscibe:
+                case MqttControlPacketType.Unsubscribe:
                     return DecodeUnsubscribePacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.UnsubAck:
                     return DecodeUnsubAckPacket(receivedMqttPacket.Body);
@@ -108,7 +108,7 @@ namespace MQTTnet.Formatter.V3
                 remainingLength += (uint)publishPacket.Payload.Length;
             }
 
-            var remainingLengthSize = MqttBufferWriter.GetLengthOfVariableInteger(remainingLength);
+            var remainingLengthSize = MqttBufferWriter.GetVariableByteIntegerSize(remainingLength);
 
             var headerSize = FixedHeaderSize + remainingLengthSize;
             var headerOffset = 5 - headerSize;
@@ -783,7 +783,7 @@ namespace MQTTnet.Formatter.V3
                 }
             }
 
-            return MqttBufferWriter.BuildFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
+            return MqttBufferWriter.BuildFixedHeader(MqttControlPacketType.Unsubscribe, 0x02);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]

Source/MQTTnet/Formatter/V5/MqttV5PacketDecoder.cs

@@ -54,7 +54,7 @@ namespace MQTTnet.Formatter.V5
                     return DecodeSubscribePacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.SubAck:
                     return DecodeSubAckPacket(receivedMqttPacket.Body);
-                case MqttControlPacketType.Unsubscibe:
+                case MqttControlPacketType.Unsubscribe:
                     return DecodeUnsubscribePacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.UnsubAck:
                     return DecodeUnsubAckPacket(receivedMqttPacket.Body);

Source/MQTTnet/Formatter/V5/MqttV5PacketEncoder.cs

@@ -12,6 +12,8 @@ namespace MQTTnet.Formatter.V5
 {
     public sealed class MqttV5PacketEncoder
     {
+        const int FixedHeaderSize = 1;
+        
         readonly MqttBufferWriter _bufferWriter;
         readonly MqttV5PropertiesWriter _propertiesWriter = new MqttV5PropertiesWriter(new MqttBufferWriter(1024, 4096));
 
@@ -40,9 +42,9 @@ namespace MQTTnet.Formatter.V5
                 remainingLength += (uint)publishPacket.Payload.Length;
             }
 
-            var remainingLengthSize = MqttBufferWriter.GetLengthOfVariableInteger(remainingLength);
+            var remainingLengthSize = MqttBufferWriter.GetVariableByteIntegerSize(remainingLength);
 
-            var headerSize = 1 + remainingLengthSize;
+            var headerSize = FixedHeaderSize + remainingLengthSize;
             var headerOffset = 5 - headerSize;
 
             // Position cursor on correct offset on beginning of array (has leading 0x0)
@@ -522,7 +524,7 @@ namespace MQTTnet.Formatter.V5
                 _bufferWriter.WriteString(topicFilter);
             }
 
-            return MqttBufferWriter.BuildFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
+            return MqttBufferWriter.BuildFixedHeader(MqttControlPacketType.Unsubscribe, 0x02);
         }
 
         static void ThrowIfPacketIdentifierIsInvalid(ushort packetIdentifier, MqttPacket packet)

Source/MQTTnet/Internal/AsyncSignal.cs

@@ -34,11 +34,12 @@ namespace MQTTnet.Internal
                 _isSignaled = true;
 
                 Cleanup();
-                
+
                 // If there is already a waiting task let it run.
                 if (_waiter != null)
                 {
                     _waiter.Approve();
+                    _waiter.Dispose();
                     _waiter = null;
 
                     // Since we already got a waiter the signal must be reset right now!
@@ -102,6 +103,8 @@ namespace MQTTnet.Internal
             // ReSharper disable once FieldCanBeMadeReadOnly.Local
             CancellationTokenRegistration _cancellationTokenRegistration;
 
+            volatile bool _isCompleted;
+
             public AsyncSignalWaiter(CancellationToken cancellationToken)
             {
                 if (cancellationToken.CanBeCanceled)
@@ -114,18 +117,37 @@ namespace MQTTnet.Internal
 
             public void Approve()
             {
+                if (_isCompleted)
+                {
+                    return;
+                }
+
+                _isCompleted = true;
                 _promise.TrySetResult(true);
             }
 
             public void Dispose()
             {
                 _cancellationTokenRegistration.Dispose();
+                
+                if (_isCompleted)
+                {
+                    // Avoid allocation of _ObjectDisposedException_ which may not be used.
+                    return;
+                }
 
+                _isCompleted = true;
                 _promise.TrySetException(new ObjectDisposedException(nameof(AsyncSignalWaiter)));
             }
 
             void Cancel()
             {
+                if (_isCompleted)
+                {
+                    return;
+                }
+
+                _isCompleted = true;
                 _promise.TrySetCanceled();
             }
         }

Source/MQTTnet/Internal/CancellationTokenSourceExtensions.cs

@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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;
+
+namespace MQTTnet.Internal
+{
+    public static class CancellationTokenSourceExtensions
+    {
+        public static bool TryCancel(this CancellationTokenSource cancellationTokenSource, bool throwOnFirstException = false)
+        {
+            if (cancellationTokenSource == null)
+            {
+                return false;
+            }
+
+            try
+            {
+                // Checking the _IsCancellationRequested_ here will not throw an
+                // "ObjectDisposedException" as the getter of the property "Token" will do!
+                if (cancellationTokenSource.IsCancellationRequested)
+                {
+                    return false;
+                }
+
+                cancellationTokenSource.Cancel(throwOnFirstException);
+                return true;
+            }
+            catch (ObjectDisposedException)
+            {
+                return false;
+            }
+        }
+    }
+}

Source/MQTTnet/Internal/MqttMemoryHelper.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace MQTTnet.Internal
+{
+    public static class MqttMemoryHelper
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void Copy(byte[] source, int sourceIndex, byte[] destination, int destinationIndex, int length)
+        {
+#if NETCOREAPP3_1_OR_GREATER || NETSTANDARD2_1
+            source.AsSpan(sourceIndex, length).CopyTo(destination.AsSpan(destinationIndex, length));
+#elif NET461_OR_GREATER || NETSTANDARD1_3_OR_GREATER
+            unsafe
+            {
+                fixed (byte* sourceHandle = &source[sourceIndex])
+                {
+                    fixed (byte* destinationHandle = &destination[destinationIndex])
+                    {
+                        System.Buffer.MemoryCopy(sourceHandle, destinationHandle, length, length);
+                    }
+                }
+            }
+#else
+            Array.Copy(source, sourceIndex, destination, destinationIndex, length);
+#endif
+        }
+    }
+}

Source/MQTTnet/MQTTnet.csproj

@@ -41,7 +41,8 @@
         <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
         <PackageLicenseExpression>MIT</PackageLicenseExpression>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
-        <NoWarn>1591</NoWarn>
+        <NoWarn>1591;NETSDK1138</NoWarn>
+        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     </PropertyGroup>
 
     <PropertyGroup Condition="'$(TargetFramework)'=='uap10.0'">

Source/MQTTnet/MqttApplicationMessageExtensions.cs

@@ -5,78 +5,13 @@
 using System;
 using System.Text;
 
-// ReSharper disable MemberCanBePrivate.Global
-
 namespace MQTTnet
 {
     public static class MqttApplicationMessageExtensions
     {
-        public static short ConvertPayloadToByte(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            if (applicationMessage.Payload.Length != 1)
-            {
-                throw new ArgumentException("Payload requires to be 1 bytes long.");
-            }
-
-            return applicationMessage.Payload[0];
-        }
-
-        public static short ConvertPayloadToInt16(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            if (applicationMessage.Payload.Length != 2)
-            {
-                throw new ArgumentException("Payload requires to be 2 bytes long.");
-            }
-
-            return BitConverter.ToInt16(applicationMessage.Payload, 0);
-        }
-
-        public static int ConvertPayloadToInt32(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            if (applicationMessage.Payload?.Length != 4)
-            {
-                throw new ArgumentException("Payload requires to be 4 bytes long.");
-            }
-
-            return BitConverter.ToInt32(applicationMessage.Payload, 0);
-        }
-
-        public static long ConvertPayloadToInt64(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            if (applicationMessage.Payload.Length != 8)
-            {
-                throw new ArgumentException("Payload requires to be 8 bytes long.");
-            }
-
-            return BitConverter.ToInt64(applicationMessage.Payload, 0);
-        }
-
         public static string ConvertPayloadToString(this MqttApplicationMessage applicationMessage)
         {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
 
             if (applicationMessage.Payload == null)
             {
@@ -90,65 +25,5 @@ namespace MQTTnet
 
             return Encoding.UTF8.GetString(applicationMessage.Payload, 0, applicationMessage.Payload.Length);
         }
-
-        public static decimal ParsePayloadToDecimal(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            return decimal.Parse(ConvertPayloadToString(applicationMessage));
-        }
-
-        public static double ParsePayloadToDouble(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            return double.Parse(ConvertPayloadToString(applicationMessage));
-        }
-
-        public static short ParsePayloadToInt16(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            return short.Parse(ConvertPayloadToString(applicationMessage));
-        }
-
-        public static int ParsePayloadToInt32(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            return int.Parse(ConvertPayloadToString(applicationMessage));
-        }
-
-        public static long ParsePayloadToInt64(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            return long.Parse(ConvertPayloadToString(applicationMessage));
-        }
-
-        public static float ParsePayloadToSingle(this MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null)
-            {
-                throw new ArgumentNullException(nameof(applicationMessage));
-            }
-
-            return float.Parse(ConvertPayloadToString(applicationMessage));
-        }
     }
-}
+}

Source/MQTTnet/Packets/MqttPacketExtensions.cs

@@ -0,0 +1,102 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Packets
+{
+    public static class MqttPacketExtensions
+    {
+        public static string GetRfcName(this MqttPacket packet)
+        {
+            if (packet == null)
+            {
+                throw new ArgumentNullException(nameof(packet));
+            }
+
+            switch (packet)
+            {
+                case MqttConnectPacket _:
+                {
+                    return "CONNECT";
+                }
+
+                case MqttConnAckPacket _:
+                {
+                    return "CONNACK";
+                }
+
+                case MqttAuthPacket _:
+                {
+                    return "AUTH";
+                }
+
+                case MqttDisconnectPacket _:
+                {
+                    return "DISCONNECT";
+                }
+
+                case MqttPingReqPacket _:
+                {
+                    return "PINGREQ";
+                }
+
+                case MqttPingRespPacket _:
+                {
+                    return "PINGRESP";
+                }
+
+                case MqttSubscribePacket _:
+                {
+                    return "SUBSCRIBE";
+                }
+
+                case MqttSubAckPacket _:
+                {
+                    return "SUBACK";
+                }
+
+                case MqttUnsubscribePacket _:
+                {
+                    return "UNSUBSCRIBE";
+                }
+
+                case MqttUnsubAckPacket _:
+                {
+                    return "UNSUBACK";
+                }
+
+                case MqttPublishPacket _:
+                {
+                    return "PUBLISH";
+                }
+
+                case MqttPubAckPacket _:
+                {
+                    return "PUBACK";
+                }
+
+                case MqttPubRelPacket _:
+                {
+                    return "PUBREL";
+                }
+
+                case MqttPubRecPacket _:
+                {
+                    return "PUBREC";
+                }
+
+                case MqttPubCompPacket _:
+                {
+                    return "PUBCOMP";
+                }
+                
+                default:
+                {
+                    return packet.GetType().Name;
+                }
+            }
+        }
+    }
+}

Source/MQTTnet/Protocol/MqttControlPacketType.cs

@@ -15,7 +15,7 @@ namespace MQTTnet.Protocol
         PubComp = 7,
         Subscribe = 8,
         SubAck = 9,
-        Unsubscibe = 10,
+        Unsubscribe = 10,
         UnsubAck = 11,
         PingReq = 12,
         PingResp = 13,

Source/MQTTnet/Server/InjectedMqttApplicationMessage.cs

@@ -12,8 +12,8 @@ namespace MQTTnet.Server
         {
             ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
         }
-        
-        public string SenderClientId { get; set; }
+
+        public string SenderClientId { get; set; } = string.Empty;
 
         public MqttApplicationMessage ApplicationMessage { get; set; }
     }

Source/MQTTnet/Server/Internal/DispatchApplicationMessageResult.cs

@@ -2,15 +2,27 @@
 // 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.Generic;
+using MQTTnet.Packets;
+
 namespace MQTTnet.Server
 {
     public sealed class DispatchApplicationMessageResult
     {
-        public DispatchApplicationMessageResult(int matchingSubscribersCount)
+        public DispatchApplicationMessageResult(int reasonCode, bool closeConnection, string reasonString, List<MqttUserProperty> userProperties)
         {
-            MatchingSubscribersCount = matchingSubscribersCount;
+            ReasonCode = reasonCode;
+            CloseConnection = closeConnection;
+            ReasonString = reasonString;
+            UserProperties = userProperties;
         }
 
-        public int MatchingSubscribersCount { get; }
+        public bool CloseConnection { get; }
+
+        public int ReasonCode { get; }
+
+        public string ReasonString { get; }
+
+        public List<MqttUserProperty> UserProperties { get; }
     }
 }

Source/MQTTnet/Server/Internal/MqttClient.cs

@@ -12,27 +12,21 @@ using MQTTnet.Diagnostics;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using MQTTnet.Internal;
-using MQTTnet.PacketDispatcher;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
 namespace MQTTnet.Server
 {
-    public sealed class MqttClient
+    public sealed class MqttClient : IDisposable
     {
-        readonly MqttApplicationMessageFactory _applicationMessageFactory = new MqttApplicationMessageFactory();
         readonly MqttConnectPacket _connectPacket;
         readonly MqttServerEventContainer _eventContainer;
         readonly MqttNetSourceLogger _logger;
-        readonly MqttPacketDispatcher _packetDispatcher = new MqttPacketDispatcher();
-        readonly MqttPacketFactories _packetFactories = new MqttPacketFactories();
-
         readonly MqttServerOptions _serverOptions;
-
         readonly MqttClientSessionsManager _sessionsManager;
         readonly Dictionary<ushort, string> _topicAlias = new Dictionary<ushort, string>();
 
-        CancellationTokenSource _cancellationToken;
+        CancellationTokenSource _cancellationToken = new CancellationTokenSource();
         bool _disconnectPacketSent;
 
         public MqttClient(
@@ -45,14 +39,13 @@ namespace MQTTnet.Server
             IMqttNetLogger logger)
         {
             _serverOptions = serverOptions ?? throw new ArgumentNullException(nameof(serverOptions));
-            _eventContainer = eventContainer;
+            _eventContainer = eventContainer ?? throw new ArgumentNullException(nameof(eventContainer));
             _sessionsManager = sessionsManager ?? throw new ArgumentNullException(nameof(sessionsManager));
+            _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
 
             ChannelAdapter = channelAdapter ?? throw new ArgumentNullException(nameof(channelAdapter));
             Endpoint = channelAdapter.Endpoint;
-
             Session = session ?? throw new ArgumentNullException(nameof(session));
-            _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
 
             if (logger == null)
             {
@@ -80,53 +73,56 @@ namespace MQTTnet.Server
 
         public MqttClientStatistics Statistics { get; } = new MqttClientStatistics();
 
+        public void Dispose()
+        {
+            _cancellationToken?.Dispose();
+        }
+
         public void ResetStatistics()
         {
             ChannelAdapter.ResetStatistics();
+            Statistics.ResetStatistics();
         }
 
         public async Task RunAsync()
         {
-            _logger.Info("Client '{0}': Session started.", Id);
+            _logger.Info("Client '{0}': Session started", Id);
 
             Session.LatestConnectPacket = _connectPacket;
             Session.WillMessageSent = false;
 
-            using (_cancellationToken = new CancellationTokenSource())
+            try
             {
                 var cancellationToken = _cancellationToken.Token;
 
-                try
-                {
-                    _ = Task.Factory.StartNew(() => SendPacketsLoop(cancellationToken), cancellationToken, TaskCreationOptions.PreferFairness, TaskScheduler.Default).ConfigureAwait(false);
+                _ = Task.Factory.StartNew(() => SendPacketsLoop(cancellationToken), cancellationToken, TaskCreationOptions.PreferFairness, TaskScheduler.Default)
+                    .ConfigureAwait(false);
 
-                    IsRunning = true;
+                IsRunning = true;
 
-                    await ReceivePackagesLoop(cancellationToken).ConfigureAwait(false);
-                }
-                finally
-                {
-                    IsRunning = false;
-
-                    _cancellationToken?.Cancel();
-                    _cancellationToken = null;
-                }
+                await ReceivePackagesLoop(cancellationToken).ConfigureAwait(false);
             }
+            finally
+            {
+                IsRunning = false;
 
-            _packetDispatcher.CancelAll();
+                _cancellationToken?.TryCancel();
+                _cancellationToken?.Dispose();
+                _cancellationToken = null;
+            }
 
             if (!IsTakenOver && !IsCleanDisconnect && Session.LatestConnectPacket.WillFlag && !Session.WillMessageSent)
             {
-                var willPublishPacket = _packetFactories.Publish.Create(Session.LatestConnectPacket);
-                var willApplicationMessage = _applicationMessageFactory.Create(willPublishPacket);
+                var willPublishPacket = MqttPacketFactories.Publish.Create(Session.LatestConnectPacket);
+                var willApplicationMessage = MqttApplicationMessageFactory.Create(willPublishPacket);
 
-                _ = _sessionsManager.DispatchApplicationMessage(Id, willApplicationMessage);
+                _ = _sessionsManager.DispatchApplicationMessage(Id, Session.Items, willApplicationMessage, CancellationToken.None);
                 Session.WillMessageSent = true;
 
-                _logger.Info("Client '{0}': Published will message.", Id);
+                _logger.Info("Client '{0}': Published will message", Id);
             }
 
-            _logger.Info("Client '{0}': Connection stopped.", Id);
+            _logger.Info("Client '{0}': Connection stopped", Id);
         }
 
         public async Task SendPacketAsync(MqttPacket packet, CancellationToken cancellationToken)
@@ -180,6 +176,12 @@ namespace MQTTnet.Server
             return CompletedTask.Instance;
         }
 
+        void HandleIncomingPingReqPacket()
+        {
+            // See: The Server MUST send a PINGRESP packet in response to a PINGREQ packet [MQTT-3.12.4-1].
+            Session.EnqueueHealthPacket(new MqttPacketBusItem(MqttPingRespPacket.Instance));
+        }
+
         Task HandleIncomingPubAckPacket(MqttPubAckPacket pubAckPacket)
         {
             var acknowledgedPublishPacket = Session.AcknowledgePublishPacket(pubAckPacket.PacketIdentifier);
@@ -208,41 +210,17 @@ namespace MQTTnet.Server
         {
             HandleTopicAlias(publishPacket);
 
-            InterceptingPublishEventArgs interceptingPublishEventArgs = null;
-            var applicationMessage = _applicationMessageFactory.Create(publishPacket);
-            var closeConnection = false;
-            var processPublish = true;
+            var applicationMessage = MqttApplicationMessageFactory.Create(publishPacket);
 
-            if (_eventContainer.InterceptingPublishEvent.HasHandlers)
-            {
-                interceptingPublishEventArgs = new InterceptingPublishEventArgs(applicationMessage, cancellationToken, Id, Session.Items);
-                if (string.IsNullOrEmpty(interceptingPublishEventArgs.ApplicationMessage.Topic))
-                {
-                    // This can happen if a topic alias us used but the topic is
-                    // unknown to the server.
-                    interceptingPublishEventArgs.Response.ReasonCode = MqttPubAckReasonCode.TopicNameInvalid;
-                    interceptingPublishEventArgs.ProcessPublish = false;
-                }
+            var dispatchApplicationMessageResult =
+                await _sessionsManager.DispatchApplicationMessage(Id, Session.Items, applicationMessage, cancellationToken).ConfigureAwait(false);
 
-                await _eventContainer.InterceptingPublishEvent.InvokeAsync(interceptingPublishEventArgs).ConfigureAwait(false);
-
-                applicationMessage = interceptingPublishEventArgs.ApplicationMessage;
-                closeConnection = interceptingPublishEventArgs.CloseConnection;
-                processPublish = interceptingPublishEventArgs.ProcessPublish;
-            }
-
-            if (closeConnection)
+            if (dispatchApplicationMessageResult.CloseConnection)
             {
                 await StopAsync(MqttDisconnectReasonCode.UnspecifiedError);
                 return;
             }
 
-            DispatchApplicationMessageResult dispatchResult = null;
-            if (processPublish && applicationMessage != null)
-            {
-                dispatchResult = await _sessionsManager.DispatchApplicationMessage(Id, applicationMessage).ConfigureAwait(false);
-            }
-
             switch (publishPacket.QualityOfServiceLevel)
             {
                 case MqttQualityOfServiceLevel.AtMostOnce:
@@ -252,19 +230,19 @@ namespace MQTTnet.Server
                 }
                 case MqttQualityOfServiceLevel.AtLeastOnce:
                 {
-                    var pubAckPacket = _packetFactories.PubAck.Create(publishPacket, interceptingPublishEventArgs, dispatchResult);
+                    var pubAckPacket = MqttPacketFactories.PubAck.Create(publishPacket, dispatchApplicationMessageResult);
                     Session.EnqueueControlPacket(new MqttPacketBusItem(pubAckPacket));
                     break;
                 }
                 case MqttQualityOfServiceLevel.ExactlyOnce:
                 {
-                    var pubRecPacket = _packetFactories.PubRec.Create(publishPacket, interceptingPublishEventArgs, dispatchResult);
+                    var pubRecPacket = MqttPacketFactories.PubRec.Create(publishPacket, dispatchApplicationMessageResult);
                     Session.EnqueueControlPacket(new MqttPacketBusItem(pubRecPacket));
                     break;
                 }
                 default:
                 {
-                    throw new MqttCommunicationException("Received a not supported QoS level.");
+                    throw new MqttCommunicationException("Received a not supported QoS level");
                 }
             }
         }
@@ -273,7 +251,7 @@ namespace MQTTnet.Server
         {
             // Do not fire the event _ClientAcknowledgedPublishPacket_ here because the QoS 2 process is only finished
             // properly when the client has sent the PUBCOMP packet.
-            var pubRelPacket = _packetFactories.PubRel.Create(pubRecPacket, MqttApplicationMessageReceivedReasonCode.Success);
+            var pubRelPacket = MqttPacketFactories.PubRel.Create(pubRecPacket, MqttApplicationMessageReceivedReasonCode.Success);
             Session.EnqueueControlPacket(new MqttPacketBusItem(pubRelPacket));
 
             return CompletedTask.Instance;
@@ -281,7 +259,7 @@ namespace MQTTnet.Server
 
         void HandleIncomingPubRelPacket(MqttPubRelPacket pubRelPacket)
         {
-            var pubCompPacket = _packetFactories.PubComp.Create(pubRelPacket, MqttApplicationMessageReceivedReasonCode.Success);
+            var pubCompPacket = MqttPacketFactories.PubComp.Create(pubRelPacket, MqttApplicationMessageReceivedReasonCode.Success);
             Session.EnqueueControlPacket(new MqttPacketBusItem(pubCompPacket));
         }
 
@@ -289,7 +267,7 @@ namespace MQTTnet.Server
         {
             var subscribeResult = await Session.Subscribe(subscribePacket, cancellationToken).ConfigureAwait(false);
 
-            var subAckPacket = _packetFactories.SubAck.Create(subscribePacket, subscribeResult);
+            var subAckPacket = MqttPacketFactories.SubAck.Create(subscribePacket, subscribeResult);
 
             Session.EnqueueControlPacket(new MqttPacketBusItem(subAckPacket));
 
@@ -303,7 +281,7 @@ namespace MQTTnet.Server
             {
                 foreach (var retainedMessageMatch in subscribeResult.RetainedMessages)
                 {
-                    var publishPacket = _packetFactories.Publish.Create(retainedMessageMatch);
+                    var publishPacket = MqttPacketFactories.Publish.Create(retainedMessageMatch);
                     Session.EnqueueDataPacket(new MqttPacketBusItem(publishPacket));
                 }
             }
@@ -313,7 +291,7 @@ namespace MQTTnet.Server
         {
             var unsubscribeResult = await Session.Unsubscribe(unsubscribePacket, cancellationToken).ConfigureAwait(false);
 
-            var unsubAckPacket = _packetFactories.UnsubAck.Create(unsubscribePacket, unsubscribeResult);
+            var unsubAckPacket = MqttPacketFactories.UnsubAck.Create(unsubscribePacket, unsubscribeResult);
 
             Session.EnqueueControlPacket(new MqttPacketBusItem(unsubAckPacket));
 
@@ -344,7 +322,7 @@ namespace MQTTnet.Server
                     }
                     else
                     {
-                        _logger.Warning("Client '{0}': Received invalid topic alias ({1}).", Id, publishPacket.TopicAlias);
+                        _logger.Warning("Client '{0}': Received invalid topic alias ({1})", Id, publishPacket.TopicAlias);
                     }
                 }
             }
@@ -370,6 +348,7 @@ namespace MQTTnet.Server
 
         async Task ReceivePackagesLoop(CancellationToken cancellationToken)
         {
+            MqttPacket currentPacket = null;
             try
             {
                 // We do not listen for the cancellation token here because the internal buffer might still
@@ -379,12 +358,12 @@ namespace MQTTnet.Server
                 {
                     await Task.Yield();
 
-                    var packet = await ChannelAdapter.ReceivePacketAsync(cancellationToken).ConfigureAwait(false);
-                    if (packet == null)
+                    currentPacket = await ChannelAdapter.ReceivePacketAsync(cancellationToken).ConfigureAwait(false);
+                    if (currentPacket == null)
                     {
                         return;
                     }
-                    
+
                     // Check for cancellation again because receive packet might block some time.
                     if (cancellationToken.IsCancellationRequested)
                     {
@@ -397,73 +376,69 @@ namespace MQTTnet.Server
                     {
                         return;
                     }
-                    
+
                     var processPacket = true;
 
                     if (_eventContainer.InterceptingInboundPacketEvent.HasHandlers)
                     {
-                        var interceptingPacketEventArgs = new InterceptingPacketEventArgs(cancellationToken, Id, Endpoint, packet, Session.Items);
+                        var interceptingPacketEventArgs = new InterceptingPacketEventArgs(cancellationToken, Id, Endpoint, currentPacket, Session.Items);
                         await _eventContainer.InterceptingInboundPacketEvent.InvokeAsync(interceptingPacketEventArgs).ConfigureAwait(false);
-                        packet = interceptingPacketEventArgs.Packet;
+                        currentPacket = interceptingPacketEventArgs.Packet;
                         processPacket = interceptingPacketEventArgs.ProcessPacket;
                     }
 
-                    if (!processPacket || packet == null)
+                    if (!processPacket || currentPacket == null)
                     {
                         // Restart the receiving process to get the next packet ignoring the current one..
                         continue;
                     }
 
-                    Statistics.HandleReceivedPacket(packet);
+                    Statistics.HandleReceivedPacket(currentPacket);
 
-                    if (packet is MqttPublishPacket publishPacket)
+                    if (currentPacket is MqttPublishPacket publishPacket)
                     {
                         await HandleIncomingPublishPacket(publishPacket, cancellationToken).ConfigureAwait(false);
                     }
-                    else if (packet is MqttPubAckPacket pubAckPacket)
+                    else if (currentPacket is MqttPubAckPacket pubAckPacket)
                     {
                         await HandleIncomingPubAckPacket(pubAckPacket).ConfigureAwait(false);
                     }
-                    else if (packet is MqttPubCompPacket pubCompPacket)
+                    else if (currentPacket is MqttPubCompPacket pubCompPacket)
                     {
                         await HandleIncomingPubCompPacket(pubCompPacket).ConfigureAwait(false);
                     }
-                    else if (packet is MqttPubRecPacket pubRecPacket)
+                    else if (currentPacket is MqttPubRecPacket pubRecPacket)
                     {
                         await HandleIncomingPubRecPacket(pubRecPacket).ConfigureAwait(false);
                     }
-                    else if (packet is MqttPubRelPacket pubRelPacket)
+                    else if (currentPacket is MqttPubRelPacket pubRelPacket)
                     {
                         HandleIncomingPubRelPacket(pubRelPacket);
                     }
-                    else if (packet is MqttSubscribePacket subscribePacket)
+                    else if (currentPacket is MqttSubscribePacket subscribePacket)
                     {
                         await HandleIncomingSubscribePacket(subscribePacket, cancellationToken).ConfigureAwait(false);
                     }
-                    else if (packet is MqttUnsubscribePacket unsubscribePacket)
+                    else if (currentPacket is MqttUnsubscribePacket unsubscribePacket)
                     {
                         await HandleIncomingUnsubscribePacket(unsubscribePacket, cancellationToken).ConfigureAwait(false);
                     }
-                    else if (packet is MqttPingReqPacket)
+                    else if (currentPacket is MqttPingReqPacket)
                     {
-                        // See: The Server MUST send a PINGRESP packet in response to a PINGREQ packet [MQTT-3.12.4-1].
-                        Session.EnqueueHealthPacket(new MqttPacketBusItem(MqttPingRespPacket.Instance));
+                        HandleIncomingPingReqPacket();
                     }
-                    else if (packet is MqttPingRespPacket)
+                    else if (currentPacket is MqttPingRespPacket)
                     {
                         throw new MqttProtocolViolationException("A PINGRESP Packet is sent by the Server to the Client in response to a PINGREQ Packet only.");
                     }
-                    else if (packet is MqttDisconnectPacket)
+                    else if (currentPacket is MqttDisconnectPacket)
                     {
                         IsCleanDisconnect = true;
                         return;
                     }
                     else
                     {
-                        if (!_packetDispatcher.TryDispatch(packet))
-                        {
-                            throw new MqttProtocolViolationException($"Received packet '{packet}' at an unexpected time.");
-                        }
+                        throw new MqttProtocolViolationException("Packet not allowed");
                     }
                 }
             }
@@ -474,11 +449,25 @@ namespace MQTTnet.Server
             {
                 if (exception is MqttCommunicationException)
                 {
-                    _logger.Warning(exception, "Client '{0}': Communication exception while receiving client packets.", Id);
+                    _logger.Warning(exception, "Client '{0}': Communication exception while receiving packets", Id);
+                    return;
+                }
+
+                var logLevel = MqttNetLogLevel.Error;
+
+                if (!IsRunning)
+                {
+                    // There was an exception but the connection is already closed. So there is no chance to send a response to the client etc.
+                    logLevel = MqttNetLogLevel.Warning;
+                }
+
+                if (currentPacket == null)
+                {
+                    _logger.Publish(logLevel, exception, "Client '{0}': Error while receiving packets", Id);
                 }
                 else
                 {
-                    _logger.Error(exception, "Client '{0}': Error while receiving client packets.", Id);
+                    _logger.Publish(logLevel, exception, "Client '{0}': Error while processing {1} packet", Id, currentPacket.GetRfcName());
                 }
             }
         }
@@ -530,15 +519,15 @@ namespace MQTTnet.Server
             {
                 if (exception is MqttCommunicationTimedOutException)
                 {
-                    _logger.Warning(exception, "Client '{0}': Sending publish packet failed: Timeout.", Id);
+                    _logger.Warning(exception, "Client '{0}': Sending PUBLISH packet failed due to timeout", Id);
                 }
                 else if (exception is MqttCommunicationException)
                 {
-                    _logger.Warning(exception, "Client '{0}': Sending publish packet failed: Communication exception.", Id);
+                    _logger.Warning(exception, "Client '{0}': Sending PUBLISH packet failed due to communication exception", Id);
                 }
                 else
                 {
-                    _logger.Error(exception, "Client '{0}': Sending publish packet failed.", Id);
+                    _logger.Error(exception, "Client '{0}': Sending PUBLISH packet failed", Id);
                 }
 
                 if (packetBusItem?.Packet is MqttPublishPacket publishPacket)
@@ -556,15 +545,7 @@ namespace MQTTnet.Server
 
         void StopInternal()
         {
-            try
-            {
-                _cancellationToken?.Cancel();
-            }
-            catch (ObjectDisposedException)
-            {
-                // This can happen when connections are created and dropped very quickly.
-                // It is not an issue if the cancellation token cannot be canceled multiple times.
-            }
+            _cancellationToken?.TryCancel();
         }
 
         async Task TrySendDisconnectPacket(MqttDisconnectReasonCode reasonCode)
@@ -573,8 +554,8 @@ namespace MQTTnet.Server
             {
                 // This also indicates that it was tried at least!
                 _disconnectPacketSent = true;
-                
-                var disconnectPacket = _packetFactories.Disconnect.Create(reasonCode);
+
+                var disconnectPacket = MqttPacketFactories.Disconnect.Create(reasonCode);
 
                 using (var timeout = new CancellationTokenSource(_serverOptions.DefaultCommunicationTimeout))
                 {
@@ -583,7 +564,7 @@ namespace MQTTnet.Server
             }
             catch (Exception exception)
             {
-                _logger.Warning(exception, "Client '{0}': Error while sending DISCONNECT packet (ReasonCode = {1}).", Id, reasonCode);
+                _logger.Warning(exception, "Client '{0}': Error while sending DISCONNECT packet (ReasonCode = {1})", Id, reasonCode);
             }
         }
     }

Source/MQTTnet/Server/Internal/MqttClientSessionsManager.cs

@@ -28,7 +28,6 @@ namespace MQTTnet.Server
         readonly MqttServerEventContainer _eventContainer;
         readonly MqttNetSourceLogger _logger;
         readonly MqttServerOptions _options;
-        readonly MqttPacketFactories _packetFactories = new MqttPacketFactories();
 
         readonly MqttRetainedMessagesManager _retainedMessagesManager;
         readonly IMqttNetLogger _rootLogger;
@@ -127,81 +126,118 @@ namespace MQTTnet.Server
 
             _logger.Verbose("Session for client '{0}' deleted.", clientId);
         }
-        
-        public async Task<DispatchApplicationMessageResult> DispatchApplicationMessage(string senderId, MqttApplicationMessage applicationMessage)
+
+        public async Task<DispatchApplicationMessageResult> DispatchApplicationMessage(
+            string senderId,
+            IDictionary senderSessionItems,
+            MqttApplicationMessage applicationMessage,
+            CancellationToken cancellationToken)
         {
-            var matchingSubscribersCount = 0;
-            try
+            var processPublish = true;
+            var closeConnection = false;
+            string reasonString = null;
+            List<MqttUserProperty> userProperties = null;
+            var reasonCode = 0; // The reason code is later converted into several different but compatible enums!
+
+            // Allow the user to intercept application message...
+            if (_eventContainer.InterceptingPublishEvent.HasHandlers)
             {
-                if (applicationMessage.Retain)
+                var interceptingPublishEventArgs = new InterceptingPublishEventArgs(applicationMessage, cancellationToken, senderId, senderSessionItems);
+                if (string.IsNullOrEmpty(interceptingPublishEventArgs.ApplicationMessage.Topic))
                 {
-                    await _retainedMessagesManager.UpdateMessage(senderId, applicationMessage).ConfigureAwait(false);
-                }
-                
-                List<MqttSession> subscriberSessions;
-                lock (_sessionsManagementLock)
-                {
-                    subscriberSessions = _subscriberSessions.ToList();
+                    // This can happen if a topic alias us used but the topic is
+                    // unknown to the server.
+                    interceptingPublishEventArgs.Response.ReasonCode = MqttPubAckReasonCode.TopicNameInvalid;
+                    interceptingPublishEventArgs.ProcessPublish = false;
                 }
 
-                // Calculate application message topic hash once for subscription checks
-                MqttSubscription.CalculateTopicHash(applicationMessage.Topic, out var topicHash, out _, out _);
+                await _eventContainer.InterceptingPublishEvent.InvokeAsync(interceptingPublishEventArgs).ConfigureAwait(false);
 
-                foreach (var session in subscriberSessions)
-                {
-                    if(!session.TryCheckSubscriptions(
-                        applicationMessage.Topic,
-                        topicHash,
-                        applicationMessage.QualityOfServiceLevel,
-                        senderId,
-                        out var checkSubscriptionsResult))
-                    {
-                        // Checking the subscriptions has failed for the session. The session
-                        // will be ignored.
-                        continue;
-                    }
-
-                    if (!checkSubscriptionsResult.IsSubscribed)
-                    {
-                        continue;
-                    }
-
-                    var newPublishPacket = _packetFactories.Publish.Create(applicationMessage);
-                    newPublishPacket.QualityOfServiceLevel = checkSubscriptionsResult.QualityOfServiceLevel;
-                    newPublishPacket.SubscriptionIdentifiers = checkSubscriptionsResult.SubscriptionIdentifiers;
-
-                    if (newPublishPacket.QualityOfServiceLevel > 0)
-                    {
-                        newPublishPacket.PacketIdentifier = session.PacketIdentifierProvider.GetNextPacketIdentifier();
-                    }
-
-                    if (checkSubscriptionsResult.RetainAsPublished)
-                    {
-                        // Transfer the original retain state from the publisher. This is a MQTTv5 feature.
-                        newPublishPacket.Retain = applicationMessage.Retain;
-                    }
-                    else
-                    {
-                        newPublishPacket.Retain = false;
-                    }
-
-                    session.EnqueueDataPacket(new MqttPacketBusItem(newPublishPacket));
-                    matchingSubscribersCount++;
-
-                    _logger.Verbose("Client '{0}': Queued PUBLISH packet with topic '{1}'.", session.Id, applicationMessage.Topic);
-                }
-
-                if (matchingSubscribersCount == 0)
-                {
-                    await FireApplicationMessageNotConsumedEvent(applicationMessage, senderId).ConfigureAwait(false);
-                }
-            }
-            catch (Exception exception)
-            {
-                _logger.Error(exception, "Unhandled exception while processing next queued application message.");
+                applicationMessage = interceptingPublishEventArgs.ApplicationMessage;
+                closeConnection = interceptingPublishEventArgs.CloseConnection;
+                processPublish = interceptingPublishEventArgs.ProcessPublish;
+                reasonString = interceptingPublishEventArgs.Response.ReasonString;
+                userProperties = interceptingPublishEventArgs.Response.UserProperties;
+                reasonCode = (int)interceptingPublishEventArgs.Response.ReasonCode;
             }
 
-            return new DispatchApplicationMessageResult(matchingSubscribersCount);
+            // Process the application message...
+            if (processPublish && applicationMessage != null)
+            {
+                var matchingSubscribersCount = 0;
+                try
+                {
+                    if (applicationMessage.Retain)
+                    {
+                        await _retainedMessagesManager.UpdateMessage(senderId, applicationMessage).ConfigureAwait(false);
+                    }
+
+                    List<MqttSession> subscriberSessions;
+                    lock (_sessionsManagementLock)
+                    {
+                        subscriberSessions = _subscriberSessions.ToList();
+                    }
+
+                    // Calculate application message topic hash once for subscription checks
+                    MqttSubscription.CalculateTopicHash(applicationMessage.Topic, out var topicHash, out _, out _);
+
+                    foreach (var session in subscriberSessions)
+                    {
+                        if (!session.TryCheckSubscriptions(
+                                applicationMessage.Topic,
+                                topicHash,
+                                applicationMessage.QualityOfServiceLevel,
+                                senderId,
+                                out var checkSubscriptionsResult))
+                        {
+                            // Checking the subscriptions has failed for the session. The session
+                            // will be ignored.
+                            continue;
+                        }
+
+                        if (!checkSubscriptionsResult.IsSubscribed)
+                        {
+                            continue;
+                        }
+
+                        var publishPacketCopy = MqttPacketFactories.Publish.Create(applicationMessage);
+                        publishPacketCopy.QualityOfServiceLevel = checkSubscriptionsResult.QualityOfServiceLevel;
+                        publishPacketCopy.SubscriptionIdentifiers = checkSubscriptionsResult.SubscriptionIdentifiers;
+
+                        if (publishPacketCopy.QualityOfServiceLevel > 0)
+                        {
+                            publishPacketCopy.PacketIdentifier = session.PacketIdentifierProvider.GetNextPacketIdentifier();
+                        }
+
+                        if (checkSubscriptionsResult.RetainAsPublished)
+                        {
+                            // Transfer the original retain state from the publisher. This is a MQTTv5 feature.
+                            publishPacketCopy.Retain = applicationMessage.Retain;
+                        }
+                        else
+                        {
+                            publishPacketCopy.Retain = false;
+                        }
+
+                        session.EnqueueDataPacket(new MqttPacketBusItem(publishPacketCopy));
+                        matchingSubscribersCount++;
+
+                        _logger.Verbose("Client '{0}': Queued PUBLISH packet with topic '{1}'.", session.Id, applicationMessage.Topic);
+                    }
+
+                    if (matchingSubscribersCount == 0)
+                    {
+                        reasonCode = (int)MqttPubAckReasonCode.NoMatchingSubscribers;
+                        await FireApplicationMessageNotConsumedEvent(applicationMessage, senderId).ConfigureAwait(false);
+                    }
+                }
+                catch (Exception exception)
+                {
+                    _logger.Error(exception, "Unhandled exception while processing next queued application message.");
+                }
+            }
+
+            return new DispatchApplicationMessageResult(reasonCode, closeConnection, reasonString, userProperties);
         }
 
         public void Dispose()
@@ -288,7 +324,7 @@ namespace MQTTnet.Server
                 }
 
                 var validatingConnectionEventArgs = await ValidateConnection(connectPacket, channelAdapter).ConfigureAwait(false);
-                var connAckPacket = _packetFactories.ConnAck.Create(validatingConnectionEventArgs);
+                var connAckPacket = MqttPacketFactories.ConnAck.Create(validatingConnectionEventArgs);
 
                 if (validatingConnectionEventArgs.ReasonCode != MqttConnectReasonCode.Success)
                 {
@@ -430,7 +466,7 @@ namespace MQTTnet.Server
             {
                 foreach (var retainedMessageMatch in subscribeResult.RetainedMessages)
                 {
-                    var publishPacket = _packetFactories.Publish.Create(retainedMessageMatch);
+                    var publishPacket = MqttPacketFactories.Publish.Create(retainedMessageMatch);
                     clientSession.EnqueueDataPacket(new MqttPacketBusItem(publishPacket));
                 }
             }
@@ -496,11 +532,11 @@ namespace MQTTnet.Server
             {
                 MqttSession oldSession;
                 MqttClient oldClient;
-                
+
                 lock (_sessionsManagementLock)
                 {
                     MqttSession session;
-                    
+
                     // Create a new session (if required).
                     if (!_sessions.TryGetValue(connectPacket.ClientId, out oldSession))
                     {
@@ -519,7 +555,7 @@ namespace MQTTnet.Server
                             _logger.Verbose("Reusing existing session of client '{0}'.", connectPacket.ClientId);
                             session = oldSession;
                             oldSession = null;
-                            
+
                             // Session persistence could change for MQTT 5 clients that reconnect with different SessionExpiryInterval
                             session.IsPersistent = sessionShouldPersist;
                             connAckPacket.IsSessionPresent = true;
@@ -528,7 +564,7 @@ namespace MQTTnet.Server
                     }
 
                     _sessions[connectPacket.ClientId] = session;
-                    
+
                     // Create a new client (always required).
                     _clients.TryGetValue(connectPacket.ClientId, out oldClient);
                     if (oldClient != null)
@@ -537,7 +573,7 @@ namespace MQTTnet.Server
                         // for a later DISCONNECT packet.
                         oldClient.IsTakenOver = true;
                     }
-                    
+
                     client = CreateClient(connectPacket, channelAdapter, session);
 
                     _clients[connectPacket.ClientId] = client;
@@ -549,19 +585,15 @@ namespace MQTTnet.Server
                     var preparingSessionEventArgs = new PreparingSessionEventArgs();
                     await _eventContainer.PreparingSessionEvent.TryInvokeAsync(preparingSessionEventArgs, _logger).ConfigureAwait(false);
                 }
-                
+
                 if (oldClient != null)
                 {
                     await oldClient.StopAsync(MqttDisconnectReasonCode.SessionTakenOver).ConfigureAwait(false);
 
                     if (_eventContainer.ClientDisconnectedEvent.HasHandlers)
                     {
-                        var eventArgs = new ClientDisconnectedEventArgs(
-                            oldClient.Id,
-                            MqttClientDisconnectType.Takeover,
-                            oldClient.Endpoint,
-                            oldClient.Session.Items);
-                        
+                        var eventArgs = new ClientDisconnectedEventArgs(oldClient.Id, MqttClientDisconnectType.Takeover, oldClient.Endpoint, oldClient.Session.Items);
+
                         await _eventContainer.ClientDisconnectedEvent.TryInvokeAsync(eventArgs, _logger).ConfigureAwait(false);
                     }
                 }

Source/MQTTnet/Server/Internal/MqttClientStatistics.cs

@@ -10,15 +10,15 @@ namespace MQTTnet.Server
 {
     public sealed class MqttClientStatistics
     {
+        long _receivedApplicationMessagesCount;
+
         // Start with 1 because the CONNACK packet is not counted here.
         long _receivedPacketsCount = 1;
+        long _sentApplicationMessagesCount;
 
         // Start with 1 because the CONNECT packet is not counted here.
         long _sentPacketsCount = 1;
 
-        long _receivedApplicationMessagesCount;
-        long _sentApplicationMessagesCount;
-
         public MqttClientStatistics()
         {
             ConnectedTimestamp = DateTime.UtcNow;
@@ -28,36 +28,36 @@ namespace MQTTnet.Server
 
             LastNonKeepAlivePacketReceivedTimestamp = ConnectedTimestamp;
         }
-        
+
         public DateTime ConnectedTimestamp { get; }
 
-        /// <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 DateTime LastNonKeepAlivePacketReceivedTimestamp { get; private set; }
 
-        public long SentApplicationMessagesCount => Interlocked.Read(ref _sentApplicationMessagesCount);
-        
+        /// <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 ReceivedApplicationMessagesCount => Interlocked.Read(ref _receivedApplicationMessagesCount);
-        
-        public long SentPacketsCount => Interlocked.Read(ref _sentPacketsCount);
-        
+
         public long ReceivedPacketsCount => Interlocked.Read(ref _receivedPacketsCount);
-        
+
+        public long SentApplicationMessagesCount => Interlocked.Read(ref _sentApplicationMessagesCount);
+
+        public long SentPacketsCount => Interlocked.Read(ref _sentPacketsCount);
+
         public void HandleReceivedPacket(MqttPacket packet)
         {
             if (packet == null)
             {
                 throw new ArgumentNullException(nameof(packet));
             }
-            
+
             // This class is tracking all values from Clients perspective!
             LastPacketSentTimestamp = DateTime.UtcNow;
 
@@ -80,7 +80,7 @@ namespace MQTTnet.Server
             {
                 throw new ArgumentNullException(nameof(packet));
             }
-            
+
             // This class is tracking all values from Clients perspective!
             LastPacketReceivedTimestamp = DateTime.UtcNow;
 
@@ -91,5 +91,13 @@ namespace MQTTnet.Server
                 Interlocked.Increment(ref _receivedApplicationMessagesCount);
             }
         }
+
+        public void ResetStatistics()
+        {
+            Interlocked.Exchange(ref _sentApplicationMessagesCount, 0);
+            Interlocked.Exchange(ref _receivedApplicationMessagesCount, 0);
+            Interlocked.Exchange(ref _sentPacketsCount, 0);
+            Interlocked.Exchange(ref _receivedPacketsCount, 0);
+        }
     }
 }

Source/MQTTnet/Server/Internal/MqttClientSubscriptionsManager.cs

@@ -55,18 +55,21 @@ namespace MQTTnet.Server
             {
                 if (_noWildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var noWildcardSubscriptions))
                 {
-                    possibleSubscriptions.AddRange(noWildcardSubscriptions.ToList());
+                    possibleSubscriptions.AddRange(noWildcardSubscriptions);
                 }
 
                 foreach (var wcs in _wildcardSubscriptionsByTopicHash)
                 {
-                    var wildcardSubscriptions = wcs.Value;
                     var subscriptionHash = wcs.Key;
-                    var subscriptionHashMask = wildcardSubscriptions.HashMask;
-
-                    if ((topicHash & subscriptionHashMask) == subscriptionHash)
+                    var subscriptionsByHashMask = wcs.Value.SubscriptionsByHashMask;
+                    foreach (var shm in subscriptionsByHashMask)
                     {
-                        possibleSubscriptions.AddRange(wildcardSubscriptions.Subscriptions.ToList());
+                        var subscriptionHashMask = shm.Key;
+                        if ((topicHash & subscriptionHashMask) == subscriptionHash)
+                        {
+                            var subscriptions = shm.Value;
+                            possibleSubscriptions.AddRange(subscriptions);
+                        }
                     }
                 }
             }
@@ -265,8 +268,8 @@ namespace MQTTnet.Server
                             {
                                 if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                                 {
-                                    subscriptions.Subscriptions.Remove(existingSubscription);
-                                    if (subscriptions.Subscriptions.Count == 0)
+                                    subscriptions.RemoveSubscription(existingSubscription);
+                                    if (subscriptions.SubscriptionsByHashMask.Count == 0)
                                     {
                                         _wildcardSubscriptionsByTopicHash.Remove(topicHash);
                                     }
@@ -346,9 +349,9 @@ namespace MQTTnet.Server
                     // must remove object from topic hash dictionary first
                     if (hasWildcard)
                     {
-                        if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subs))
+                        if (_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                         {
-                            subs.Subscriptions.Remove(existingSubscription);
+                            subscriptions.RemoveSubscription(existingSubscription);
                             // no need to remove empty entry because we'll be adding subscription again below
                         }
                     }
@@ -370,11 +373,11 @@ namespace MQTTnet.Server
                 {
                     if (!_wildcardSubscriptionsByTopicHash.TryGetValue(topicHash, out var subscriptions))
                     {
-                        subscriptions = new TopicHashMaskSubscriptions(topicHashMask);
+                        subscriptions = new TopicHashMaskSubscriptions();
                         _wildcardSubscriptionsByTopicHash.Add(topicHash, subscriptions);
                     }
 
-                    subscriptions.Subscriptions.Add(subscription);
+                    subscriptions.AddSubscription(subscription);
                 }
                 else
                 {

Source/MQTTnet/Server/Internal/TopicHashMaskSubscriptions.cs

@@ -3,17 +3,32 @@ using System.Collections.Generic;
 namespace MQTTnet.Server
 {
     /// <summary>
-    ///     Helper class that stores the topic hash mask common to all contained Subscriptions for direct access.
+    ///     Helper class that stores subscriptions by their topic hash mask.
     /// </summary>
     public sealed class TopicHashMaskSubscriptions
     {
-        public TopicHashMaskSubscriptions(ulong hashMask)
+        public Dictionary<ulong, HashSet<MqttSubscription>> SubscriptionsByHashMask { get; } = new Dictionary<ulong, HashSet<MqttSubscription>>();
+
+        public void AddSubscription(MqttSubscription subscription)
         {
-            HashMask = hashMask;
+            if (!SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
+            {
+                subscriptions = new HashSet<MqttSubscription>();
+                SubscriptionsByHashMask.Add(subscription.TopicHashMask, subscriptions);
+            }
+            subscriptions.Add(subscription);
         }
 
-        public ulong HashMask { get; }
-
-        public HashSet<MqttSubscription> Subscriptions { get; } = new HashSet<MqttSubscription>();
+        public void RemoveSubscription(MqttSubscription subscription)
+        {
+            if (SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
+            {
+                subscriptions.Remove(subscription);
+                if (subscriptions.Count == 0)
+                {
+                    SubscriptionsByHashMask.Remove(subscription.TopicHashMask);
+                }
+            }
+        }
     }
 }

Source/MQTTnet/Server/MqttServer.cs

@@ -19,17 +19,17 @@ namespace MQTTnet.Server
 {
     public class MqttServer : Disposable
     {
-        readonly MqttServerEventContainer _eventContainer = new MqttServerEventContainer();
-
-        readonly IDictionary _sessionItems = new ConcurrentDictionary<object, object>();
         readonly ICollection<IMqttServerAdapter> _adapters;
         readonly MqttClientSessionsManager _clientSessionsManager;
+        readonly MqttServerEventContainer _eventContainer = new MqttServerEventContainer();
         readonly MqttServerKeepAliveMonitor _keepAliveMonitor;
         readonly MqttNetSourceLogger _logger;
         readonly MqttServerOptions _options;
         readonly MqttRetainedMessagesManager _retainedMessagesManager;
         readonly IMqttNetLogger _rootLogger;
 
+        readonly IDictionary _sessionItems = new ConcurrentDictionary<object, object>();
+
         CancellationTokenSource _cancellationTokenSource;
 
         public MqttServer(MqttServerOptions options, IEnumerable<IMqttServerAdapter> adapters, IMqttNetLogger logger)
@@ -207,7 +207,7 @@ namespace MQTTnet.Server
             return _clientSessionsManager.GetSessionStatusAsync();
         }
 
-        public async Task InjectApplicationMessage(InjectedMqttApplicationMessage injectedApplicationMessage)
+        public Task InjectApplicationMessage(InjectedMqttApplicationMessage injectedApplicationMessage, CancellationToken cancellationToken = default)
         {
             if (injectedApplicationMessage == null)
             {
@@ -223,34 +223,16 @@ namespace MQTTnet.Server
 
             ThrowIfNotStarted();
 
-            var processPublish = true;
-            var applicationMessage = injectedApplicationMessage.ApplicationMessage;
-
-            if (_eventContainer.InterceptingPublishEvent.HasHandlers)
-            {
-                var interceptingPublishEventArgs = new InterceptingPublishEventArgs(
-                    applicationMessage,
-                    _cancellationTokenSource.Token,
-                    injectedApplicationMessage.SenderClientId,
-                    _sessionItems);
-
-                await _eventContainer.InterceptingPublishEvent.InvokeAsync(interceptingPublishEventArgs).ConfigureAwait(false);
-
-                applicationMessage = interceptingPublishEventArgs.ApplicationMessage;
-                processPublish = interceptingPublishEventArgs.ProcessPublish;
-            }
-
-            if (!processPublish)
-            {
-                return;
-            }
-            
-            if (string.IsNullOrEmpty(applicationMessage.Topic))
+            if (string.IsNullOrEmpty(injectedApplicationMessage.ApplicationMessage.Topic))
             {
                 throw new NotSupportedException("Injected application messages must contain a topic. Topic alias is not supported.");
             }
-            
-            await _clientSessionsManager.DispatchApplicationMessage(injectedApplicationMessage.SenderClientId, applicationMessage).ConfigureAwait(false);
+
+            return _clientSessionsManager.DispatchApplicationMessage(
+                injectedApplicationMessage.SenderClientId,
+                _sessionItems,
+                injectedApplicationMessage.ApplicationMessage,
+                cancellationToken);
         }
 
         public async Task StartAsync()

Source/MQTTnet/Server/PublishResponse.cs

@@ -14,6 +14,6 @@ namespace MQTTnet.Server
         
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; }
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }