Enable nullable

* Call the event handler also for retained messages

* Update release notes

* Add Unit Test

.github/workflows/ci.yml

@@ -3,8 +3,8 @@ name: CI
 on: [push, pull_request]
 
 env:
-  VERSION: "5.0.0.${{github.run_number}}"
-  PACKAGE_SUFFIX: "-RC"
+  VERSION: "5.1.0.${{github.run_number}}"
+  PACKAGE_SUFFIX: ""
 
 jobs:
   build:
@@ -21,8 +21,15 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
+      - name: Load strong name certificate
+        run: |
+          echo "$SNC_BASE64" | base64 --decode > "${{ github.workspace }}/certificate.snk"
+        shell: bash
+        env:
+          SNC_BASE64: ${{ secrets.SNC_BASE64 }}
+
       - name: Build package
-        run: dotnet build MQTTnet.sln --configuration Release /p:FileVersion=${{ env.VERSION }} /p:AssemblyVersion=${{ env.VERSION }} /p:PackageVersion=${{ env.VERSION }}${{ env.PACKAGE_SUFFIX }}
+        run: dotnet build MQTTnet.sln --configuration Release /p:FileVersion=${{ env.VERSION }} /p:AssemblyVersion=${{ env.VERSION }} /p:PackageVersion=${{ env.VERSION }}${{ env.PACKAGE_SUFFIX }} /p:SignAssembly=true /p:AssemblyOriginatorKeyFile=${{ github.workspace }}/certificate.snk
 
       - name: Upload nuget packages
         uses: actions/upload-artifact@v4
@@ -46,7 +53,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Execute tests
-        run: dotnet test --framework net8.0 Source/MQTTnet.Tests/MQTTnet.Tests.csproj
+        run: dotnet test --framework net8.0 --configuration Release Source/MQTTnet.Tests/MQTTnet.Tests.csproj
 
   sign:
     needs: build
@@ -107,7 +114,8 @@ jobs:
         run: dotnet nuget push ${{ github.workspace }}/nugets/**/*.nupkg -k ${{ secrets.MYGET_API_KEY }} -s https://www.myget.org/F/mqttnet/api/v3/index.json --skip-duplicate
 
   publish-nuget:
-    if: ${{ github.event_name == 'published' }}
+    # Tag schema is 'v5.0.0-rc' etc.
+    if: startsWith(github.ref, 'refs/tags/v')
     needs: [sign, test]
     runs-on: ubuntu-latest
 

Directory.Build.props

@@ -0,0 +1,9 @@
+<Project>
+
+  <PropertyGroup>
+    <TestingPlatformShowTestsFailure>true</TestingPlatformShowTestsFailure>
+    <TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>
+    <EnableMSTestRunner>true</EnableMSTestRunner>
+  </PropertyGroup>
+
+</Project>

MQTTnet.sln.DotSettings

@@ -1,4 +1,8 @@
 <wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertIfStatementToSwitchStatement/@EntryIndexedValue">DO_NOT_SHOW</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=InconsistentNaming/@EntryIndexedValue">SUGGESTION</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UncatchableException/@EntryIndexedValue">DO_NOT_SHOW</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UnthrowableException/@EntryIndexedValue">DO_NOT_SHOW</s:String>
 	<s:String x:Key="/Default/CodeStyle/CodeFormatting/CSharpCodeStyle/BRACES_FOR_FOR/@EntryValue">Required</s:String>
 	<s:String x:Key="/Default/CodeStyle/CodeFormatting/CSharpCodeStyle/BRACES_FOR_FOREACH/@EntryValue">Required</s:String>
 	<s:String x:Key="/Default/CodeStyle/CodeFormatting/CSharpCodeStyle/BRACES_FOR_IFELSE/@EntryValue">Required</s:String>

README.md

@@ -3,9 +3,9 @@
 <br/>
 </p>
 
-[![NuGet Badge](https://buildstats.info/nuget/MQTTnet)](https://www.nuget.org/packages/MQTTnet)
+[![NuGet Badge](https://img.shields.io/nuget/dt/MQTTnet)](https://www.nuget.org/packages/MQTTnet)
 [![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)
+[![MyGet](https://img.shields.io/myget/mqttnet/v/mqttnet?color=orange&label=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)
 [![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)](https://raw.githubusercontent.com/dotnet/MQTTnet/master/LICENSE)

Samples/Client/Client_Connection_Samples.cs

@@ -8,431 +8,17 @@
 
 using System.Security.Authentication;
 using System.Security.Cryptography.X509Certificates;
+using System.Text;
 using MQTTnet.Formatter;
+using MQTTnet.Protocol;
 using MQTTnet.Samples.Helpers;
+using MQTTnet.Server;
+using MQTTnet.Server.EnhancedAuthentication;
 
 namespace MQTTnet.Samples.Client;
 
 public static class Client_Connection_Samples
 {
-    public static async Task Clean_Disconnect()
-    {
-        /*
-         * This sample disconnects in a clean way. This will send a MQTT DISCONNECT packet
-         * to the server and close the connection afterwards.
-         *
-         * See sample _Connect_Client_ for more details.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            // This will send the DISCONNECT packet. Calling _Dispose_ without DisconnectAsync the
-            // connection is closed in a "not clean" way. See MQTT specification for more details.
-            await mqttClient.DisconnectAsync(new MqttClientDisconnectOptionsBuilder().WithReason(MqttClientDisconnectOptionsReason.NormalDisconnection).Build());
-        }
-    }
-
-    public static async Task Connect_Client()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to a public broker.
-         *
-         * Always dispose the client when it is no longer used.
-         * The default version of MQTT is 3.1.1.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            // Use builder classes where possible in this project.
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-
-            // This will throw an exception if the server is not available.
-            // The result from this message returns additional data which was sent
-            // from the server. Please refer to the MQTT protocol specification for details.
-            var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            Console.WriteLine("The MQTT client is connected.");
-
-            response.DumpToConsole();
-
-            // Send a clean disconnect to the server by calling _DisconnectAsync_. Without this the TCP connection
-            // gets dropped and the server will handle this as a non clean disconnect (see MQTT spec for details).
-            var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder().Build();
-
-            await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
-        }
-    }
-
-    public static async Task Connect_Client_Timeout()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to an invalid broker using a timeout.
-         *
-         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();
-
-            try
-            {
-                using (var timeoutToken = new CancellationTokenSource(TimeSpan.FromSeconds(1)))
-                {
-                    await mqttClient.ConnectAsync(mqttClientOptions, timeoutToken.Token);
-                }
-            }
-            catch (OperationCanceledException)
-            {
-                Console.WriteLine("Timeout while connecting.");
-            }
-        }
-    }
-
-    public static async Task Connect_Client_Using_MQTTv5()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to a public broker using MQTTv5.
-         *
-         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").WithProtocolVersion(MqttProtocolVersion.V500).Build();
-
-            // In MQTTv5 the response contains much more information.
-            var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            Console.WriteLine("The MQTT client is connected.");
-
-            response.DumpToConsole();
-        }
-    }
-
-    public static async Task Connect_Client_Using_TLS_1_2()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to a public broker using TLS 1.2 encryption.
-         *
-         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io")
-                .WithTlsOptions(
-                    o =>
-                    {
-                        // The used public broker sometimes has invalid certificates. This sample accepts all
-                        // certificates. This should not be used in live environments.
-                        o.WithCertificateValidationHandler(_ => true);
-
-                        // The default value is determined by the OS. Set manually to force version.
-                        o.WithSslProtocols(SslProtocols.Tls12);
-                    })
-                .Build();
-
-            using (var timeout = new CancellationTokenSource(5000))
-            {
-                await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
-
-                Console.WriteLine("The MQTT client is connected.");
-            }
-        }
-    }
-
-    public static async Task Connect_Client_Using_WebSockets()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to a public broker using a WebSocket connection.
-         *
-         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithWebSocketServer(o => o.WithUri("broker.hivemq.com:8000/mqtt")).Build();
-
-            var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            Console.WriteLine("The MQTT client is connected.");
-
-            response.DumpToConsole();
-        }
-    }
-
-    public static async Task Connect_Client_With_TLS_Encryption()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to a public broker with enabled TLS encryption.
-         *
-         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883)
-                .WithTlsOptions(
-                    o => o.WithCertificateValidationHandler(
-                        // The used public broker sometimes has invalid certificates. This sample accepts all
-                        // certificates. This should not be used in live environments.
-                        _ => true))
-                .Build();
-
-            // In MQTTv5 the response contains much more information.
-            using (var timeout = new CancellationTokenSource(5000))
-            {
-                var response = await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
-
-                Console.WriteLine("The MQTT client is connected.");
-
-                response.DumpToConsole();
-            }
-        }
-    }
-
-    public static async Task Connect_With_Amazon_AWS()
-    {
-        /*
-         * This sample creates a simple MQTT client and connects to an Amazon Web Services broker.
-         *
-         * The broker requires special settings which are set here.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("amazon.web.services.broker")
-                // Disabling packet fragmentation is very important!
-                .WithoutPacketFragmentation()
-                .Build();
-
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            Console.WriteLine("The MQTT client is connected.");
-
-            await mqttClient.DisconnectAsync();
-        }
-    }
-
-    public static async Task Disconnect_Clean()
-    {
-        /*
-         * This sample disconnects from the server with sending a DISCONNECT packet.
-         * This way of disconnecting is treated as a clean disconnect which will not
-         * trigger sending the last will etc.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            // Calling _DisconnectAsync_ will send a DISCONNECT packet before closing the connection.
-            // Using a reason code requires MQTT version 5.0.0!
-            await mqttClient.DisconnectAsync(MqttClientDisconnectOptionsReason.ImplementationSpecificError);
-        }
-    }
-
-    public static async Task Disconnect_Non_Clean()
-    {
-        /*
-         * This sample disconnects from the server without sending a DISCONNECT packet.
-         * This way of disconnecting is treated as a non clean disconnect which will
-         * trigger sending the last will etc.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        var mqttClient = mqttFactory.CreateMqttClient();
-
-        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-
-        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-        // Calling _Dispose_ or use of a _using_ statement will close the transport connection
-        // without sending a DISCONNECT packet to the server.
-        mqttClient.Dispose();
-    }
-
-    public static async Task Inspect_Certificate_Validation_Errors()
-    {
-        /*
-         * This sample prints the certificate information while connection. This data can be used to decide whether a connection is secure or not
-         * including the reason for that status.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io", 8883)
-                .WithTlsOptions(
-                    o =>
-                    {
-                        o.WithCertificateValidationHandler(
-                            eventArgs =>
-                            {
-                                eventArgs.Certificate.Subject.DumpToConsole();
-                                eventArgs.Certificate.GetExpirationDateString().DumpToConsole();
-                                eventArgs.Chain.ChainPolicy.RevocationMode.DumpToConsole();
-                                eventArgs.Chain.ChainStatus.DumpToConsole();
-                                eventArgs.SslPolicyErrors.DumpToConsole();
-                                return true;
-                            });
-                    })
-                .Build();
-
-            // In MQTTv5 the response contains much more information.
-            using (var timeout = new CancellationTokenSource(5000))
-            {
-                await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
-            }
-        }
-    }
-
-    public static async Task Ping_Server()
-    {
-        /*
-         * This sample sends a PINGREQ packet to the server and waits for a reply.
-         *
-         * This is only supported in MQTTv5.0.0+.
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-            // This will throw an exception if the server does not reply.
-            await mqttClient.PingAsync(CancellationToken.None);
-
-            Console.WriteLine("The MQTT server replied to the ping request.");
-        }
-    }
-
-    public static async Task Reconnect_Using_Event()
-    {
-        /*
-         * This sample shows how to reconnect when the connection was dropped.
-         * This approach uses one of the events from the client.
-         * This approach has a risk of dead locks! Consider using the timer approach (see sample).
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-
-            mqttClient.DisconnectedAsync += async e =>
-            {
-                if (e.ClientWasConnected)
-                {
-                    // Use the current options as the new options.
-                    await mqttClient.ConnectAsync(mqttClient.Options);
-                }
-            };
-
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-        }
-    }
-
-    public static void Reconnect_Using_Timer()
-    {
-        /*
-         * This sample shows how to reconnect when the connection was dropped.
-         * This approach uses a custom Task/Thread which will monitor the connection status.
-         * This is the recommended way but requires more custom code!
-         */
-
-        var mqttFactory = new MqttClientFactory();
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
-
-            _ = Task.Run(
-                async () =>
-                {
-                    // User proper cancellation and no while(true).
-                    while (true)
-                    {
-                        try
-                        {
-                            // This code will also do the very first connect! So no call to _ConnectAsync_ is required in the first place.
-                            if (!await mqttClient.TryPingAsync())
-                            {
-                                await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-
-                                // Subscribe to topics when session is clean etc.
-                                Console.WriteLine("The MQTT client is connected.");
-                            }
-                        }
-                        catch
-                        {
-                            // Handle the exception properly (logging etc.).
-                        }
-                        finally
-                        {
-                            // Check the connection state every 5 seconds and perform a reconnect if required.
-                            await Task.Delay(TimeSpan.FromSeconds(5));
-                        }
-                    }
-                });
-
-            Console.WriteLine("Press <Enter> to exit");
-            Console.ReadLine();
-        }
-    }
-
-    public static async Task ConnectTls_WithCaFile()
-    {
-        var mqttFactory = new MqttClientFactory();
-
-        X509Certificate2Collection caChain = new X509Certificate2Collection();
-        caChain.ImportFromPem(mosquitto_org); // from https://test.mosquitto.org/ssl/mosquitto.org.crt
-
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder()
-                .WithTcpServer("test.mosquitto.org", 8883)
-                .WithTlsOptions(new MqttClientTlsOptionsBuilder()
-                    .WithTrustChain(caChain)
-                    .Build())
-                .Build();
-
-            var connAck = await mqttClient.ConnectAsync(mqttClientOptions);
-            Console.WriteLine("Connected to test.moquitto.org:8883 with CaFile mosquitto.org.crt: " + connAck.ResultCode);
-        }
-
-
-    }
     const string mosquitto_org = @"
 -----BEGIN CERTIFICATE-----
 MIIEAzCCAuugAwIBAgIUBY1hlCGvdj4NhBXkZ/uLUZNILAwwDQYJKoZIhvcNAQEL
@@ -460,4 +46,477 @@ m/XriWr/Cq4h/JfB7NTsezVslgkBaoU=
 -----END CERTIFICATE-----
 ";
 
+    public static async Task Clean_Disconnect()
+    {
+        /*
+         * This sample disconnects in a clean way. This will send a MQTT DISCONNECT packet
+         * to the server and close the connection afterward.
+         *
+         * See sample _Connect_Client_ for more details.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        // This will send the DISCONNECT packet. Calling _Dispose_ without DisconnectAsync the
+        // connection is closed in a "not clean" way. See MQTT specification for more details.
+        await mqttClient.DisconnectAsync(new MqttClientDisconnectOptionsBuilder().WithReason(MqttClientDisconnectOptionsReason.NormalDisconnection).Build());
+    }
+
+    public static async Task Connect()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to a public broker.
+         *
+         * Always dispose the client when it is no longer used.
+         * The default version of MQTT is 3.1.1.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        // Use builder classes where possible in this project.
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        // This will throw an exception if the server is not available.
+        // The result from this message returns additional data which was sent
+        // from the server. Please refer to the MQTT protocol specification for details.
+        var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        Console.WriteLine("The MQTT client is connected.");
+
+        response.DumpToConsole();
+
+        // Send a clean disconnect to the server by calling _DisconnectAsync_. Without this the TCP connection
+        // gets dropped and the server will handle this as a non clean disconnect (see MQTT spec for details).
+        var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder().Build();
+
+        await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
+    }
+
+    public static async Task Connect_Using_Enhanced_Authentication()
+    {
+        /*
+         * This sample uses enhanced authentication (Kerberos) when creating the connection.
+         */
+
+
+        /*
+         * Server part...
+         */
+
+        var mqttServerFactory = new MqttServerFactory();
+
+        var serverOptions = mqttServerFactory.CreateServerOptionsBuilder().WithDefaultEndpoint().Build();
+        var server = mqttServerFactory.CreateMqttServer(serverOptions);
+
+        server.ValidatingConnectionAsync += async args =>
+        {
+            if (args.AuthenticationMethod == "GS2-KRB5")
+            {
+                var result = await args.ExchangeEnhancedAuthenticationAsync(new ExchangeEnhancedAuthenticationOptions(), args.CancellationToken);
+
+                Console.WriteLine($"Received AUTH data from client: {Encoding.UTF8.GetString(result.AuthenticationData)}");
+
+                var authOptions = mqttServerFactory.CreateExchangeExtendedAuthenticationOptionsBuilder().WithAuthenticationData("reply context token").Build();
+
+                result = await args.ExchangeEnhancedAuthenticationAsync(authOptions, args.CancellationToken);
+
+                Console.WriteLine($"Received AUTH data from client: {Encoding.UTF8.GetString(result.AuthenticationData)}");
+
+                args.ResponseAuthenticationData = "outcome of authentication"u8.ToArray();
+
+                // Authentication DONE!
+                args.ReasonCode = MqttConnectReasonCode.Success; // Also the default!
+            }
+            else
+            {
+                args.ReasonCode = MqttConnectReasonCode.BadAuthenticationMethod;
+            }
+        };
+
+        await server.StartAsync();
+
+        /*
+         * Client part...
+         */
+
+        var mqttClientFactory = new MqttClientFactory();
+
+        // Use Kerberos sample from the MQTT RFC.
+        var kerberosAuthenticationHandler = new SampleClientKerberosAuthenticationHandler();
+
+        var clientOptions = mqttClientFactory.CreateClientOptionsBuilder()
+            .WithTcpServer("localhost")
+            .WithProtocolVersion(MqttProtocolVersion.V500)
+            .WithEnhancedAuthenticationHandler(kerberosAuthenticationHandler)
+            .WithEnhancedAuthentication("GS2-KRB5")
+            .Build();
+
+        var client = mqttClientFactory.CreateMqttClient();
+
+        var result = await client.ConnectAsync(clientOptions);
+
+        Console.WriteLine($"Client connect result: {result.ResultCode}");
+    }
+
+    public static async Task Connect_Using_MQTTv5()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to a public broker using MQTTv5.
+         *
+         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").WithProtocolVersion(MqttProtocolVersion.V500).Build();
+
+        // In MQTTv5 the response contains much more information.
+        var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        Console.WriteLine("The MQTT client is connected.");
+
+        response.DumpToConsole();
+    }
+
+    public static async Task Connect_Using_TLS_1_2()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to a public broker using TLS 1.2 encryption.
+         *
+         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io")
+            .WithTlsOptions(
+                o =>
+                {
+                    // The used public broker sometimes has invalid certificates. This sample accepts all
+                    // certificates. This should not be used in live environments.
+                    o.WithCertificateValidationHandler(_ => true);
+
+                    // The default value is determined by the OS. Set manually to force version.
+                    o.WithSslProtocols(SslProtocols.Tls12);
+                })
+            .Build();
+
+        using var timeout = new CancellationTokenSource(5000);
+        await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
+
+        Console.WriteLine("The MQTT client is connected.");
+    }
+
+    public static async Task Connect_Using_TLS_Encryption()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to a public broker with enabled TLS encryption.
+         *
+         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883)
+            .WithTlsOptions(
+                o => o.WithCertificateValidationHandler(
+                    // The used public broker sometimes has invalid certificates. This sample accepts all
+                    // certificates. This should not be used in live environments.
+                    _ => true))
+            .Build();
+
+        // In MQTTv5 the response contains much more information.
+        using var timeout = new CancellationTokenSource(5000);
+        var response = await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
+
+        Console.WriteLine("The MQTT client is connected.");
+
+        response.DumpToConsole();
+    }
+
+    public static async Task Connect_Using_TLS_With_CA_File()
+    {
+        var mqttFactory = new MqttClientFactory();
+
+        var caChain = new X509Certificate2Collection();
+        caChain.ImportFromPem(mosquitto_org); // from https://test.mosquitto.org/ssl/mosquitto.org.crt
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883)
+            .WithTlsOptions(new MqttClientTlsOptionsBuilder().WithTrustChain(caChain).Build())
+            .Build();
+
+        var connAck = await mqttClient.ConnectAsync(mqttClientOptions);
+        Console.WriteLine("Connected to test.moquitto.org:8883 with CaFile mosquitto.org.crt: " + connAck.ResultCode);
+    }
+
+    public static async Task Connect_Using_WebSockets()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to a public broker using a WebSocket connection.
+         *
+         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithWebSocketServer(o => o.WithUri("broker.hivemq.com:8000/mqtt")).Build();
+
+        var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        Console.WriteLine("The MQTT client is connected.");
+
+        response.DumpToConsole();
+    }
+
+    public static async Task Connect_With_Amazon_AWS()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to an Amazon Web Services broker.
+         *
+         * The broker requires special settings which are set here.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("amazon.web.services.broker")
+            // Disabling packet fragmentation is very important!
+            .WithoutPacketFragmentation()
+            .Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        Console.WriteLine("The MQTT client is connected.");
+
+        await mqttClient.DisconnectAsync();
+    }
+
+    public static async Task Disconnect_Clean()
+    {
+        /*
+         * This sample disconnects from the server with sending a DISCONNECT packet.
+         * This way of disconnecting is treated as a clean disconnect which will not
+         * trigger sending the last will etc.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        // Calling _DisconnectAsync_ will send a DISCONNECT packet before closing the connection.
+        // Using a reason code requires MQTT version 5.0.0!
+        await mqttClient.DisconnectAsync(MqttClientDisconnectOptionsReason.ImplementationSpecificError);
+    }
+
+    public static async Task Disconnect_Non_Clean()
+    {
+        /*
+         * This sample disconnects from the server without sending a DISCONNECT packet.
+         * This way of disconnecting is treated as a non-clean disconnect which will
+         * trigger sending the last will etc.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        var mqttClient = mqttFactory.CreateMqttClient();
+
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        // Calling _Dispose_ or use of a _using_ statement will close the transport connection
+        // without sending a DISCONNECT packet to the server.
+        mqttClient.Dispose();
+    }
+
+    public static async Task Inspect_Certificate_Validation_Errors()
+    {
+        /*
+         * This sample prints the certificate information while connection. This data can be used to decide whether a connection is secure or not
+         * including the reason for that status.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io", 8883)
+            .WithTlsOptions(
+                o =>
+                {
+                    o.WithCertificateValidationHandler(
+                        eventArgs =>
+                        {
+                            eventArgs.Certificate.Subject.DumpToConsole();
+                            eventArgs.Certificate.GetExpirationDateString().DumpToConsole();
+                            eventArgs.Chain.ChainPolicy.RevocationMode.DumpToConsole();
+                            eventArgs.Chain.ChainStatus.DumpToConsole();
+                            eventArgs.SslPolicyErrors.DumpToConsole();
+                            return true;
+                        });
+                })
+            .Build();
+
+        // In MQTTv5 the response contains much more information.
+        using var timeout = new CancellationTokenSource(5000);
+        await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
+    }
+
+    public static async Task Ping_Server()
+    {
+        /*
+         * This sample sends a PINGREQ packet to the server and waits for a reply.
+         *
+         * This is only supported in MQTTv5.0.0+.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        // This will throw an exception if the server does not reply.
+        await mqttClient.PingAsync(CancellationToken.None);
+
+        Console.WriteLine("The MQTT server replied to the ping request.");
+    }
+
+    public static async Task Reconnect_Using_Event()
+    {
+        /*
+         * This sample shows how to reconnect when the connection was dropped.
+         * This approach uses one of the events from the client.
+         * This approach has a risk of deadlocks! Consider using the timer approach (see sample).
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        mqttClient.DisconnectedAsync += async e =>
+        {
+            if (e.ClientWasConnected)
+            {
+                // Use the current options as the new options.
+                await mqttClient.ConnectAsync(mqttClientOptions);
+            }
+        };
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+    }
+
+    public static void Reconnect_Using_Timer()
+    {
+        /*
+         * This sample shows how to reconnect when the connection was dropped.
+         * This approach uses a custom Task/Thread which will monitor the connection status.
+         * This is the recommended way but requires more custom code!
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        _ = Task.Run(
+            async () =>
+            {
+                // User proper cancellation and no while(true).
+                while (true)
+                {
+                    try
+                    {
+                        // This code will also do the very first connect! So no call to _ConnectAsync_ is required in the first place.
+                        if (!await mqttClient.TryPingAsync())
+                        {
+                            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+                            // Subscribe to topics when session is clean etc.
+                            Console.WriteLine("The MQTT client is connected.");
+                        }
+                    }
+                    catch
+                    {
+                        // Handle the exception properly (logging etc.).
+                    }
+                    finally
+                    {
+                        // Check the connection state every 5 seconds and perform a reconnect if required.
+                        await Task.Delay(TimeSpan.FromSeconds(5));
+                    }
+                }
+            });
+
+        Console.WriteLine("Press <Enter> to exit");
+        Console.ReadLine();
+    }
+
+    public static async Task Timeout()
+    {
+        /*
+         * This sample creates a simple MQTT client and connects to an invalid broker using a timeout.
+         *
+         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();
+
+        try
+        {
+            using var timeoutToken = new CancellationTokenSource(TimeSpan.FromSeconds(1));
+            await mqttClient.ConnectAsync(mqttClientOptions, timeoutToken.Token);
+        }
+        catch (OperationCanceledException)
+        {
+            Console.WriteLine("Timeout while connecting.");
+        }
+    }
+
+    class SampleClientKerberosAuthenticationHandler : IMqttEnhancedAuthenticationHandler
+    {
+        public async Task HandleEnhancedAuthenticationAsync(MqttEnhancedAuthenticationEventArgs eventArgs)
+        {
+            if (eventArgs.AuthenticationMethod != "GS2-KRB5")
+            {
+                throw new InvalidOperationException("Wrong authentication method");
+            }
+
+            var sendOptions = new SendMqttEnhancedAuthenticationDataOptions
+            {
+                Data = "initial context token"u8.ToArray()
+            };
+
+            await eventArgs.SendAsync(sendOptions);
+
+            var response = await eventArgs.ReceiveAsync(CancellationToken.None);
+
+            Console.WriteLine($"Received AUTH data from server: {Encoding.UTF8.GetString(response.AuthenticationData)}");
+
+            // No further data is required, but we have to fulfil the exchange.
+            sendOptions = new SendMqttEnhancedAuthenticationDataOptions
+            {
+                Data = []
+            };
+
+            await eventArgs.SendAsync(sendOptions, CancellationToken.None);
+        }
+    }
 }

Samples/Client/Client_Publish_Samples.cs

@@ -23,25 +23,23 @@ public static class Client_Publish_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder()
-                .WithTcpServer("broker.hivemq.com")
-                .Build();
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder()
+            .WithTcpServer("broker.hivemq.com")
+            .Build();
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            var applicationMessage = new MqttApplicationMessageBuilder()
-                .WithTopic("samples/temperature/living_room")
-                .WithPayload("19.5")
-                .Build();
+        var applicationMessage = new MqttApplicationMessageBuilder()
+            .WithTopic("samples/temperature/living_room")
+            .WithPayload("19.5")
+            .Build();
 
-            await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
+        await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
 
-            await mqttClient.DisconnectAsync();
+        await mqttClient.DisconnectAsync();
 
-            Console.WriteLine("MQTT application message is published.");
-        }
+        Console.WriteLine("MQTT application message is published.");
     }
 
     public static async Task Publish_Multiple_Application_Messages()
@@ -54,38 +52,36 @@ public static class Client_Publish_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder()
-                .WithTcpServer("broker.hivemq.com")
-                .Build();
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder()
+            .WithTcpServer("broker.hivemq.com")
+            .Build();
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            var applicationMessage = new MqttApplicationMessageBuilder()
-                .WithTopic("samples/temperature/living_room")
-                .WithPayload("19.5")
-                .Build();
+        var applicationMessage = new MqttApplicationMessageBuilder()
+            .WithTopic("samples/temperature/living_room")
+            .WithPayload("19.5")
+            .Build();
 
-            await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
+        await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
 
-            applicationMessage = new MqttApplicationMessageBuilder()
-                .WithTopic("samples/temperature/living_room")
-                .WithPayload("20.0")
-                .Build();
+        applicationMessage = new MqttApplicationMessageBuilder()
+            .WithTopic("samples/temperature/living_room")
+            .WithPayload("20.0")
+            .Build();
 
-            await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
+        await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
 
-            applicationMessage = new MqttApplicationMessageBuilder()
-                .WithTopic("samples/temperature/living_room")
-                .WithPayload("21.0")
-                .Build();
+        applicationMessage = new MqttApplicationMessageBuilder()
+            .WithTopic("samples/temperature/living_room")
+            .WithPayload("21.0")
+            .Build();
 
-            await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
+        await mqttClient.PublishAsync(applicationMessage, CancellationToken.None);
 
-            await mqttClient.DisconnectAsync();
+        await mqttClient.DisconnectAsync();
 
-            Console.WriteLine("MQTT application message is published.");
-        }
+        Console.WriteLine("MQTT application message is published.");
     }
 }

Samples/Client/Client_Subscribe_Samples.cs

@@ -26,32 +26,30 @@ public static class Client_Subscribe_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        // Setup message handling before connecting so that queued messages
+        // are also handled properly. When there is no event handler attached all
+        // received messages get lost.
+        mqttClient.ApplicationMessageReceivedAsync += e =>
         {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+            Console.WriteLine("Received application message.");
+            e.DumpToConsole();
 
-            // Setup message handling before connecting so that queued messages
-            // are also handled properly. When there is no event handler attached all
-            // received messages get lost.
-            mqttClient.ApplicationMessageReceivedAsync += e =>
-            {
-                Console.WriteLine("Received application message.");
-                e.DumpToConsole();
+            return Task.CompletedTask;
+        };
 
-                return Task.CompletedTask;
-            };
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "2")).Build();
 
-            var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "2")).Build();
+        await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
-            await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+        Console.WriteLine("MQTT client subscribed to topic.");
 
-            Console.WriteLine("MQTT client subscribed to topic.");
-
-            Console.WriteLine("Press enter to exit.");
-            Console.ReadLine();
-        }
+        Console.WriteLine("Press enter to exit.");
+        Console.ReadLine();
     }
 
     public static async Task Send_Responses()
@@ -62,36 +60,34 @@ public static class Client_Subscribe_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        mqttClient.ApplicationMessageReceivedAsync += delegate(MqttApplicationMessageReceivedEventArgs args)
         {
-            mqttClient.ApplicationMessageReceivedAsync += delegate(MqttApplicationMessageReceivedEventArgs args)
-            {
-                // Do some work with the message...
+            // Do some work with the message...
 
-                // Now respond to the broker with a reason code other than success.
-                args.ReasonCode = MqttApplicationMessageReceivedReasonCode.ImplementationSpecificError;
-                args.ResponseReasonString = "That did not work!";
+            // Now respond to the broker with a reason code other than success.
+            args.ReasonCode = MqttApplicationMessageReceivedReasonCode.ImplementationSpecificError;
+            args.ResponseReasonString = "That did not work!";
 
-                // User properties require MQTT v5!
-                args.ResponseUserProperties.Add(new MqttUserProperty("My", "Data"));
+            // User properties require MQTT v5!
+            args.ResponseUserProperties.Add(new MqttUserProperty("My", "Data"));
 
-                // Now the broker will resend the message again.
-                return Task.CompletedTask;
-            };
+            // Now the broker will resend the message again.
+            return Task.CompletedTask;
+        };
 
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "1")).Build();
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "1")).Build();
 
-            var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+        var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
-            Console.WriteLine("MQTT client subscribed to topic.");
+        Console.WriteLine("MQTT client subscribed to topic.");
 
-            // The response contains additional data sent by the server after subscribing.
-            response.DumpToConsole();
-        }
+        // The response contains additional data sent by the server after subscribing.
+        response.DumpToConsole();
     }
 
     public static async Task Subscribe_Multiple_Topics()
@@ -102,27 +98,25 @@ public static class Client_Subscribe_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            // Create the subscribe options including several topics with different options.
-            // It is also possible to all of these topics using a dedicated call of _SubscribeAsync_ per topic.
-            var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
-                .WithTopicTemplate(sampleTemplate.WithParameter("id", "1"))
-                .WithTopicTemplate(sampleTemplate.WithParameter("id", "2"), noLocal: true)
-                .WithTopicTemplate(sampleTemplate.WithParameter("id", "3"), retainHandling: MqttRetainHandling.SendAtSubscribe)
-                .Build();
+        // Create the subscribe options including several topics with different options.
+        // It is also possible to all of these topics using a dedicated call of _SubscribeAsync_ per topic.
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
+            .WithTopicTemplate(sampleTemplate.WithParameter("id", "1"))
+            .WithTopicTemplate(sampleTemplate.WithParameter("id", "2"), noLocal: true)
+            .WithTopicTemplate(sampleTemplate.WithParameter("id", "3"), retainHandling: MqttRetainHandling.SendAtSubscribe)
+            .Build();
 
-            var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+        var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
-            Console.WriteLine("MQTT client subscribed to topics.");
+        Console.WriteLine("MQTT client subscribed to topics.");
 
-            // The response contains additional data sent by the server after subscribing.
-            response.DumpToConsole();
-        }
+        // The response contains additional data sent by the server after subscribing.
+        response.DumpToConsole();
     }
 
     public static async Task Subscribe_Topic()
@@ -133,21 +127,19 @@ public static class Client_Subscribe_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "1")).Build();
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "1")).Build();
 
-            var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+        var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
-            Console.WriteLine("MQTT client subscribed to topic.");
+        Console.WriteLine("MQTT client subscribed to topic.");
 
-            // The response contains additional data sent by the server after subscribing.
-            response.DumpToConsole();
-        }
+        // The response contains additional data sent by the server after subscribing.
+        response.DumpToConsole();
     }
 
     static void ConcurrentProcessingDisableAutoAcknowledge(CancellationToken shutdownToken, IMqttClient mqttClient)

Samples/Diagnostics/Logger_Samples.cs

@@ -26,17 +26,15 @@ public static class Logger_Samples
             .WithTcpServer("broker.hivemq.com")
             .Build();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            Console.WriteLine("MQTT client is connected.");
+        Console.WriteLine("MQTT client is connected.");
 
-            var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()
-                .Build();
+        var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()
+            .Build();
 
-            await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
-        }
+        await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
     }
 
     public static async Task Use_Event_Logger()
@@ -50,7 +48,7 @@ public static class Logger_Samples
         // The logger ID is optional but can be set do distinguish different logger instances.
         var mqttEventLogger = new MqttNetEventLogger("MyCustomLogger");
 
-        mqttEventLogger.LogMessagePublished += (sender, args) =>
+        mqttEventLogger.LogMessagePublished += (_, args) =>
         {
             var output = new StringBuilder();
             output.AppendLine($">> [{args.LogMessage.Timestamp:O}] [{args.LogMessage.ThreadId}] [{args.LogMessage.Source}] [{args.LogMessage.Level}]: {args.LogMessage.Message}");
@@ -68,17 +66,15 @@ public static class Logger_Samples
             .WithTcpServer("broker.hivemq.com")
             .Build();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            Console.WriteLine("MQTT client is connected.");
+        Console.WriteLine("MQTT client is connected.");
 
-            var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()
-                .Build();
+        var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()
+            .Build();
 
-            await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
-        }
+        await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
     }
 
     sealed class MyLogger : IMqttNetLogger

Samples/Diagnostics/PackageInspection_Samples.cs

@@ -20,23 +20,21 @@ public static class PackageInspection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
-        {
-            var mqttClientOptions = mqttFactory.CreateClientOptionsBuilder()
-                .WithTcpServer("broker.hivemq.com")
-                .Build();
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = mqttFactory.CreateClientOptionsBuilder()
+            .WithTcpServer("broker.hivemq.com")
+            .Build();
 
-            mqttClient.InspectPacketAsync += OnInspectPacket;
+        mqttClient.InspectPacketAsync += OnInspectPacket;
 
-            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-            Console.WriteLine("MQTT client is connected.");
+        Console.WriteLine("MQTT client is connected.");
 
-            var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()
-                .Build();
+        var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()
+            .Build();
 
-            await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
-        }
+        await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
     }
 
     static Task OnInspectPacket(InspectMqttPacketEventArgs eventArgs)

Samples/MQTTnet.Samples.csproj

@@ -15,6 +15,7 @@
         <NuGetAudit>true</NuGetAudit>
         <NuGetAuditLevel>low</NuGetAuditLevel>
         <AnalysisLevel>latest-Recommended</AnalysisLevel>
+        <LangVersion>default</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>

Samples/RpcClient/RpcClient_Samples.cs

@@ -26,23 +26,21 @@ public static class RpcClient_Samples
         // The RPC client is an addon for the existing client. So we need a regular client
         // which is wrapped later.
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder()
+            .WithTcpServer("broker.hivemq.com")
+            .Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions);
+
+        using (var mqttRpcClient = mqttFactory.CreateMqttRpcClient(mqttClient))
         {
-            var mqttClientOptions = new MqttClientOptionsBuilder()
-                .WithTcpServer("broker.hivemq.com")
-                .Build();
-
-            await mqttClient.ConnectAsync(mqttClientOptions);
-
-            using (var mqttRpcClient = mqttFactory.CreateMqttRpcClient(mqttClient))
-            {
-                // Access to a fully featured application message is not supported for RPC calls!
-                // The method will throw an exception when the response was not received in time.
-                await mqttRpcClient.ExecuteAsync(TimeSpan.FromSeconds(2), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
-            }
-
-            Console.WriteLine("The RPC call was successful.");
+            // Access to a fully featured application message is not supported for RPC calls!
+            // The method will throw an exception when the response was not received in time.
+            await mqttRpcClient.ExecuteAsync(TimeSpan.FromSeconds(2), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
         }
+
+        Console.WriteLine("The RPC call was successful.");
     }
 
     /*

Samples/Server/Server_Diagnostics_Samples.cs

@@ -25,28 +25,26 @@ public static class Server_Diagnostics_Samples
         var mqttServerFactory = new MqttServerFactory();
         var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        // Attach the event handler.
+        mqttServer.ClientAcknowledgedPublishPacketAsync += e =>
         {
-            // Attach the event handler.
-            mqttServer.ClientAcknowledgedPublishPacketAsync += e =>
-            {
-                Console.WriteLine($"Client '{e.ClientId}' acknowledged packet {e.PublishPacket.PacketIdentifier} with topic '{e.PublishPacket.Topic}'");
+            Console.WriteLine($"Client '{e.ClientId}' acknowledged packet {e.PublishPacket.PacketIdentifier} with topic '{e.PublishPacket.Topic}'");
 
-                // It is also possible to read additional data from the client response. This requires casting the response packet.
-                var qos1AcknowledgePacket = e.AcknowledgePacket as MqttPubAckPacket;
-                Console.WriteLine($"QoS 1 reason code: {qos1AcknowledgePacket?.ReasonCode}");
+            // It is also possible to read additional data from the client response. This requires casting the response packet.
+            var qos1AcknowledgePacket = e.AcknowledgePacket as MqttPubAckPacket;
+            Console.WriteLine($"QoS 1 reason code: {qos1AcknowledgePacket?.ReasonCode}");
 
-                var qos2AcknowledgePacket = e.AcknowledgePacket as MqttPubCompPacket;
-                Console.WriteLine($"QoS 2 reason code: {qos1AcknowledgePacket?.ReasonCode}");
-                return CompletedTask.Instance;
-            };
+            var qos2AcknowledgePacket = e.AcknowledgePacket as MqttPubCompPacket;
+            Console.WriteLine($"QoS 2 reason code: {qos2AcknowledgePacket?.ReasonCode}");
+            return CompletedTask.Instance;
+        };
 
-            await mqttServer.StartAsync();
+        await mqttServer.StartAsync();
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
 
-            await mqttServer.StopAsync();
-        }
+        await mqttServer.StopAsync();
     }
 }

Samples/Server/Server_Intercepting_Samples.cs

@@ -25,23 +25,21 @@ public static class Server_Intercepting_Samples
         var mqttServerFactory = new MqttServerFactory();
         var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        mqttServer.InterceptingPublishAsync += args =>
         {
-            mqttServer.InterceptingPublishAsync += args =>
-            {
-                // Here we only change the topic of the received application message.
-                // but also changing the payload etc. is required. Changing the QoS after
-                // transmitting is not supported and makes no sense at all.
-                args.ApplicationMessage.Topic += "/manipulated";
+            // Here we only change the topic of the received application message.
+            // but also changing the payload etc. is required. Changing the QoS after
+            // transmitting is not supported and makes no sense at all.
+            args.ApplicationMessage.Topic += "/manipulated";
 
-                return CompletedTask.Instance;
-            };
+            return CompletedTask.Instance;
+        };
 
-            await mqttServer.StartAsync();
+        await mqttServer.StartAsync();
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
-            await mqttServer.StopAsync();
-        }
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
+        await mqttServer.StopAsync();
     }
 }

Samples/Server/Server_Retained_Messages_Samples.cs

@@ -29,64 +29,62 @@ public static class Server_Retained_Messages_Samples
         // Due to security reasons the "default" endpoint (which is unencrypted) is not enabled by default!
         var mqttServerOptions = mqttServerFactory.CreateServerOptionsBuilder().WithDefaultEndpoint().Build();
 
-        using (var server = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var server = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        // Make sure that the server will load the retained messages.
+        server.LoadingRetainedMessageAsync += async eventArgs =>
         {
-            // Make sure that the server will load the retained messages.
-            server.LoadingRetainedMessageAsync += async eventArgs =>
+            try
             {
-                try
-                {
-                    var models = await JsonSerializer.DeserializeAsync<List<MqttRetainedMessageModel>>(File.OpenRead(storePath)) ?? new List<MqttRetainedMessageModel>();
-                    var retainedMessages = models.Select(m => m.ToApplicationMessage()).ToList();
+                var models = await JsonSerializer.DeserializeAsync<List<MqttRetainedMessageModel>>(File.OpenRead(storePath)) ?? new List<MqttRetainedMessageModel>();
+                var retainedMessages = models.Select(m => m.ToApplicationMessage()).ToList();
 
-                    eventArgs.LoadedRetainedMessages = retainedMessages;
-                    Console.WriteLine("Retained messages loaded.");
-                }
-                catch (FileNotFoundException)
-                {
-                    // Ignore because nothing is stored yet.
-                    Console.WriteLine("No retained messages stored yet.");
-                }
-                catch (Exception exception)
-                {
-                    Console.WriteLine(exception);
-                }
-            };
-
-            // Make sure to persist the changed retained messages.
-            server.RetainedMessageChangedAsync += async eventArgs =>
+                eventArgs.LoadedRetainedMessages = retainedMessages;
+                Console.WriteLine("Retained messages loaded.");
+            }
+            catch (FileNotFoundException)
             {
-                try
-                {
-                    // This sample uses the property _StoredRetainedMessages_ which will contain all(!) retained messages.
-                    // The event args also contain the affected retained message (property ChangedRetainedMessage). This can be
-                    // used to write all retained messages to dedicated files etc. Then all files must be loaded and a full list
-                    // of retained messages must be provided in the loaded event.
-
-                    var models = eventArgs.StoredRetainedMessages.Select(MqttRetainedMessageModel.Create);
-
-                    var buffer = JsonSerializer.SerializeToUtf8Bytes(models);
-                    await File.WriteAllBytesAsync(storePath, buffer);
-                    Console.WriteLine("Retained messages saved.");
-                }
-                catch (Exception exception)
-                {
-                    Console.WriteLine(exception);
-                }
-            };
-
-            // Make sure to clear the retained messages when they are all deleted via API.
-            server.RetainedMessagesClearedAsync += _ =>
+                // Ignore because nothing is stored yet.
+                Console.WriteLine("No retained messages stored yet.");
+            }
+            catch (Exception exception)
             {
-                File.Delete(storePath);
-                return Task.CompletedTask;
-            };
+                Console.WriteLine(exception);
+            }
+        };
 
-            await server.StartAsync();
+        // Make sure to persist the changed retained messages.
+        server.RetainedMessageChangedAsync += async eventArgs =>
+        {
+            try
+            {
+                // This sample uses the property _StoredRetainedMessages_ which will contain all(!) retained messages.
+                // The event args also contain the affected retained message (property ChangedRetainedMessage). This can be
+                // used to write all retained messages to dedicated files etc. Then all files must be loaded and a full list
+                // of retained messages must be provided in the loaded event.
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
-        }
+                var models = eventArgs.StoredRetainedMessages.Select(MqttRetainedMessageModel.Create);
+
+                var buffer = JsonSerializer.SerializeToUtf8Bytes(models);
+                await File.WriteAllBytesAsync(storePath, buffer);
+                Console.WriteLine("Retained messages saved.");
+            }
+            catch (Exception exception)
+            {
+                Console.WriteLine(exception);
+            }
+        };
+
+        // Make sure to clear the retained messages when they are all deleted via API.
+        server.RetainedMessagesClearedAsync += _ =>
+        {
+            File.Delete(storePath);
+            return Task.CompletedTask;
+        };
+
+        await server.StartAsync();
+
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
     }
 
     sealed class MqttRetainedMessageModel
@@ -102,10 +100,7 @@ public static class Server_Retained_Messages_Samples
 
         public static MqttRetainedMessageModel Create(MqttApplicationMessage message)
         {
-            if (message == null)
-            {
-                throw new ArgumentNullException(nameof(message));
-            }
+            ArgumentNullException.ThrowIfNull(message);
 
             return new MqttRetainedMessageModel
             {

Samples/Server/Server_Simple_Samples.cs

@@ -22,17 +22,15 @@ public static class Server_Simple_Samples
          * See _Run_Minimal_Server_ for more information.
          */
 
-        using (var mqttServer = await StartMqttServer())
-        {
-            // Let the client connect.
-            await Task.Delay(TimeSpan.FromSeconds(5));
+        using var mqttServer = await StartMqttServer();
+        // Let the client connect.
+        await Task.Delay(TimeSpan.FromSeconds(5));
 
-            // Now disconnect the client (if connected).
-            var affectedClient = (await mqttServer.GetClientsAsync()).FirstOrDefault(c => c.Id == "MyClient");
-            if (affectedClient != null)
-            {
-                await affectedClient.DisconnectAsync();
-            }
+        // Now disconnect the client (if connected).
+        var affectedClient = (await mqttServer.GetClientsAsync()).FirstOrDefault(c => c.Id == "MyClient");
+        if (affectedClient != null)
+        {
+            await affectedClient.DisconnectAsync();
         }
     }
 
@@ -44,18 +42,16 @@ public static class Server_Simple_Samples
          * See _Run_Minimal_Server_ for more information.
          */
 
-        using (var mqttServer = await StartMqttServer())
-        {
-            // Create a new message using the builder as usual.
-            var message = new MqttApplicationMessageBuilder().WithTopic("HelloWorld").WithPayload("Test").Build();
+        using var mqttServer = await StartMqttServer();
+        // Create a new message using the builder as usual.
+        var message = new MqttApplicationMessageBuilder().WithTopic("HelloWorld").WithPayload("Test").Build();
 
-            // Now inject the new message at the broker.
-            await mqttServer.InjectApplicationMessage(
-                new InjectedMqttApplicationMessage(message)
-                {
-                    SenderClientId = "SenderClientId"
-                });
-        }
+        // Now inject the new message at the broker.
+        await mqttServer.InjectApplicationMessage(
+            new InjectedMqttApplicationMessage(message)
+            {
+                SenderClientId = "SenderClientId"
+            });
     }
 
     public static async Task Run_Minimal_Server()
@@ -77,16 +73,14 @@ public static class Server_Simple_Samples
         //     .WithDefaultEndpointPort(1234)
         //     .Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
-        {
-            await mqttServer.StartAsync();
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        await mqttServer.StartAsync();
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
 
-            // Stop and dispose the MQTT server if it is no longer needed!
-            await mqttServer.StopAsync();
-        }
+        // Stop and dispose the MQTT server if it is no longer needed!
+        await mqttServer.StopAsync();
     }
 
     public static async Task Run_Server_With_Logging()
@@ -103,16 +97,14 @@ public static class Server_Simple_Samples
 
         var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
-        {
-            await mqttServer.StartAsync();
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        await mqttServer.StartAsync();
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
 
-            // Stop and dispose the MQTT server if it is no longer needed!
-            await mqttServer.StopAsync();
-        }
+        // Stop and dispose the MQTT server if it is no longer needed!
+        await mqttServer.StopAsync();
     }
 
     public static async Task Validating_Connections()
@@ -127,37 +119,35 @@ public static class Server_Simple_Samples
 
         var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        // Setup connection validation before starting the server so that there is
+        // no change to connect without valid credentials.
+        mqttServer.ValidatingConnectionAsync += e =>
         {
-            // Setup connection validation before starting the server so that there is
-            // no change to connect without valid credentials.
-            mqttServer.ValidatingConnectionAsync += e =>
+            if (e.ClientId != "ValidClientId")
             {
-                if (e.ClientId != "ValidClientId")
-                {
-                    e.ReasonCode = MqttConnectReasonCode.ClientIdentifierNotValid;
-                }
+                e.ReasonCode = MqttConnectReasonCode.ClientIdentifierNotValid;
+            }
 
-                if (e.UserName != "ValidUser")
-                {
-                    e.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
-                }
+            if (e.UserName != "ValidUser")
+            {
+                e.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
+            }
 
-                if (e.Password != "SecretPassword")
-                {
-                    e.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
-                }
+            if (e.Password != "SecretPassword")
+            {
+                e.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
+            }
 
-                return Task.CompletedTask;
-            };
+            return Task.CompletedTask;
+        };
 
-            await mqttServer.StartAsync();
+        await mqttServer.StartAsync();
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
 
-            await mqttServer.StopAsync();
-        }
+        await mqttServer.StopAsync();
     }
 
     static async Task<MqttServer> StartMqttServer()

Samples/Server/Server_TLS_Samples.cs

@@ -31,16 +31,14 @@ public static class Server_TLS_Samples
 
         var mqttServerOptions = new MqttServerOptionsBuilder().WithEncryptionCertificate(certificate).WithEncryptedEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
-        {
-            await mqttServer.StartAsync();
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        await mqttServer.StartAsync();
 
-            Console.WriteLine("Press Enter to exit.");
-            Console.ReadLine();
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
 
-            // Stop and dispose the MQTT server if it is no longer needed!
-            await mqttServer.StopAsync();
-        }
+        // Stop and dispose the MQTT server if it is no longer needed!
+        await mqttServer.StopAsync();
     }
 
     static X509Certificate2 CreateSelfSignedCertificate(string oid)
@@ -50,26 +48,22 @@ public static class Server_TLS_Samples
         sanBuilder.AddIpAddress(IPAddress.IPv6Loopback);
         sanBuilder.AddDnsName("localhost");
 
-        using (var rsa = RSA.Create())
-        {
-            var certRequest = new CertificateRequest("CN=localhost", rsa, HashAlgorithmName.SHA512, RSASignaturePadding.Pkcs1);
+        using var rsa = RSA.Create();
+        var certRequest = new CertificateRequest("CN=localhost", rsa, HashAlgorithmName.SHA512, RSASignaturePadding.Pkcs1);
 
-            certRequest.CertificateExtensions.Add(
-                new X509KeyUsageExtension(X509KeyUsageFlags.DataEncipherment | X509KeyUsageFlags.KeyEncipherment | X509KeyUsageFlags.DigitalSignature, false));
+        certRequest.CertificateExtensions.Add(
+            new X509KeyUsageExtension(X509KeyUsageFlags.DataEncipherment | X509KeyUsageFlags.KeyEncipherment | X509KeyUsageFlags.DigitalSignature, false));
 
-            certRequest.CertificateExtensions.Add(new X509EnhancedKeyUsageExtension(new OidCollection { new(oid) }, false));
+        certRequest.CertificateExtensions.Add(new X509EnhancedKeyUsageExtension(new OidCollection { new(oid) }, false));
 
-            certRequest.CertificateExtensions.Add(sanBuilder.Build());
+        certRequest.CertificateExtensions.Add(sanBuilder.Build());
 
-            using (var certificate = certRequest.CreateSelfSigned(DateTimeOffset.Now.AddMinutes(-10), DateTimeOffset.Now.AddMinutes(10)))
-            {
-                var pfxCertificate = new X509Certificate2(
-                    certificate.Export(X509ContentType.Pfx),
-                    (string)null!,
-                    X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.Exportable);
+        using var certificate = certRequest.CreateSelfSigned(DateTimeOffset.Now.AddMinutes(-10), DateTimeOffset.Now.AddMinutes(10));
+        var pfxCertificate = new X509Certificate2(
+            certificate.Export(X509ContentType.Pfx),
+            (string)null!,
+            X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.Exportable);
 
-                return pfxCertificate;
-            }
-        }
+        return pfxCertificate;
     }
 }

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

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

Source/MQTTnet.AspnetCore/ApplicationBuilderExtensions.cs

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

Source/MQTTnet.AspnetCore/ConnectionBuilderExtensions.cs

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

Source/MQTTnet.AspnetCore/EndpointRouterExtensions.cs

@@ -6,22 +6,17 @@ using System;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Routing;
 
-namespace MQTTnet.AspNetCore
+namespace MQTTnet.AspNetCore;
+
+public static class EndpointRouterExtensions
 {
-    public static class EndpointRouterExtensions
+    public static void MapMqtt(this IEndpointRouteBuilder endpoints, string pattern)
     {
-        public static void MapMqtt(this IEndpointRouteBuilder endpoints, string pattern)
+        ArgumentNullException.ThrowIfNull(endpoints);
+
+        endpoints.MapConnectionHandler<MqttConnectionHandler>(pattern, options =>
         {
-            if (endpoints == null)
-            {
-                throw new ArgumentNullException(nameof(endpoints));
-            }
-
-            endpoints.MapConnectionHandler<MqttConnectionHandler>(pattern, options =>
-            {
-                options.WebSockets.SubProtocolSelector = MqttSubProtocolSelector.SelectSubProtocol;
-            });
-        }
+            options.WebSockets.SubProtocolSelector = MqttSubProtocolSelector.SelectSubProtocol;
+        });
     }
-}
-
+}

Source/MQTTnet.AspnetCore/MQTTnet.AspNetCore.csproj

@@ -26,7 +26,7 @@
         <PackageIcon>nuget.png</PackageIcon>
         <EmbedUntrackedSources>true</EmbedUntrackedSources>
         <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <PackageLicenseExpression>MIT</PackageLicenseExpression>
+        <PackageLicenseFile>LICENSE</PackageLicenseFile>
         <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
@@ -38,13 +38,14 @@
         <NuGetAuditLevel>low</NuGetAuditLevel>
         <NuGetAuditLevel>low</NuGetAuditLevel>
         <AnalysisLevel>latest-Recommended</AnalysisLevel>
+        <IsAotCompatible>true</IsAotCompatible>
+        <LangVersion>default</LangVersion>
+        <Nullable>enable</Nullable>
     </PropertyGroup>
 
     <ItemGroup>
-        <None Include="..\..\Images\nuget.png">
-            <Pack>True</Pack>
-            <PackagePath>\</PackagePath>
-        </None>
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
+        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.AspnetCore/MqttClientConnectionContextFactory.cs

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

Source/MQTTnet.AspnetCore/MqttConnectionContext.cs

@@ -61,21 +61,21 @@ public sealed class MqttConnectionContext : IMqttChannelAdapter
         }
     }
 
-    public string Endpoint
+    public EndPoint RemoteEndPoint
     {
         get
         {
             // mqtt over tcp
             if (_connection.RemoteEndPoint != null)
             {
-                return _connection.RemoteEndPoint.ToString();
+                return _connection.RemoteEndPoint;
             }
 
             // mqtt over websocket
             var httpFeature = _connection.Features.Get<IHttpConnectionFeature>();
             if (httpFeature?.RemoteIpAddress != null)
             {
-                return new IPEndPoint(httpFeature.RemoteIpAddress, httpFeature.RemotePort).ToString();
+                return new IPEndPoint(httpFeature.RemoteIpAddress, httpFeature.RemotePort);
             }
 
             return null;

Source/MQTTnet.AspnetCore/MqttConnectionHandler.cs

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

Source/MQTTnet.AspnetCore/MqttSubProtocolSelector.cs

@@ -13,10 +13,7 @@ public static class MqttSubProtocolSelector
 {
     public static string SelectSubProtocol(HttpRequest request)
     {
-        if (request == null)
-        {
-            throw new ArgumentNullException(nameof(request));
-        }
+        ArgumentNullException.ThrowIfNull(request);
 
         string subProtocol = null;
         if (request.Headers.TryGetValue("Sec-WebSocket-Protocol", out var requestedSubProtocolValues))
@@ -29,10 +26,7 @@ public static class MqttSubProtocolSelector
 
     public static string SelectSubProtocol(IList<string> requestedSubProtocolValues)
     {
-        if (requestedSubProtocolValues == null)
-        {
-            throw new ArgumentNullException(nameof(requestedSubProtocolValues));
-        }
+        ArgumentNullException.ThrowIfNull(requestedSubProtocolValues);
 
         // Order the protocols to also match "mqtt", "mqttv-3.1", "mqttv-3.11" etc.
         return requestedSubProtocolValues.OrderByDescending(p => p.Length).FirstOrDefault(p => p.ToLower().StartsWith("mqtt"));

Source/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Net;
 using System.Net.WebSockets;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
@@ -26,12 +27,10 @@ public sealed class MqttWebSocketServerAdapter : IMqttServerAdapter
 
     public async Task RunWebSocketConnectionAsync(WebSocket webSocket, HttpContext httpContext)
     {
-        if (webSocket == null)
-        {
-            throw new ArgumentNullException(nameof(webSocket));
-        }
+        ArgumentNullException.ThrowIfNull(webSocket);
 
-        var endpoint = $"{httpContext.Connection.RemoteIpAddress}:{httpContext.Connection.RemotePort}";
+        var remoteAddress = httpContext.Connection.RemoteIpAddress;
+        var remoteEndPoint = remoteAddress == null ? null : new IPEndPoint(remoteAddress, httpContext.Connection.RemotePort);
 
         var clientCertificate = await httpContext.Connection.GetClientCertificateAsync().ConfigureAwait(false);
         try
@@ -42,12 +41,10 @@ public sealed class MqttWebSocketServerAdapter : IMqttServerAdapter
             if (clientHandler != null)
             {
                 var formatter = new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535));
-                var channel = new MqttWebSocketChannel(webSocket, endpoint, isSecureConnection, clientCertificate);
+                var channel = new MqttWebSocketChannel(webSocket, remoteEndPoint, isSecureConnection, clientCertificate);
 
-                using (var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger))
-                {
-                    await clientHandler(channelAdapter).ConfigureAwait(false);
-                }
+                using var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger);
+                await clientHandler(channelAdapter).ConfigureAwait(false);
             }
         }
         finally

Source/MQTTnet.AspnetCore/ReaderExtensions.cs

@@ -22,10 +22,7 @@ public static class ReaderExtensions
         out SequencePosition observed,
         out int bytesRead)
     {
-        if (formatter == null)
-        {
-            throw new ArgumentNullException(nameof(formatter));
-        }
+        ArgumentNullException.ThrowIfNull(formatter);
 
         packet = null;
         consumed = input.Start;

Source/MQTTnet.AspnetCore/ServiceCollectionExtensions.cs

@@ -16,15 +16,8 @@ public static class ServiceCollectionExtensions
 {
     public static IServiceCollection AddHostedMqttServer(this IServiceCollection services, MqttServerOptions options)
     {
-        if (services == null)
-        {
-            throw new ArgumentNullException(nameof(services));
-        }
-
-        if (options == null)
-        {
-            throw new ArgumentNullException(nameof(options));
-        }
+        ArgumentNullException.ThrowIfNull(services);
+        ArgumentNullException.ThrowIfNull(options);
 
         services.AddSingleton(options);
         services.AddHostedMqttServer();
@@ -34,10 +27,7 @@ public static class ServiceCollectionExtensions
 
     public static IServiceCollection AddHostedMqttServer(this IServiceCollection services, Action<MqttServerOptionsBuilder> configure)
     {
-        if (services == null)
-        {
-            throw new ArgumentNullException(nameof(services));
-        }
+        ArgumentNullException.ThrowIfNull(services);
 
         var serverOptionsBuilder = new MqttServerOptionsBuilder();
 
@@ -61,10 +51,7 @@ public static class ServiceCollectionExtensions
 
     public static IServiceCollection AddHostedMqttServerWithServices(this IServiceCollection services, Action<AspNetMqttServerOptionsBuilder> configure)
     {
-        if (services == null)
-        {
-            throw new ArgumentNullException(nameof(services));
-        }
+        ArgumentNullException.ThrowIfNull(services);
 
         services.AddSingleton(
             s =>
@@ -89,20 +76,14 @@ public static class ServiceCollectionExtensions
 
     public static void AddMqttLogger(this IServiceCollection services, IMqttNetLogger logger)
     {
-        if (services == null)
-        {
-            throw new ArgumentNullException(nameof(services));
-        }
+        ArgumentNullException.ThrowIfNull(services);
 
         services.AddSingleton(logger);
     }
 
     public static IServiceCollection AddMqttServer(this IServiceCollection serviceCollection, Action<MqttServerOptionsBuilder> configure = null)
     {
-        if (serviceCollection is null)
-        {
-            throw new ArgumentNullException(nameof(serviceCollection));
-        }
+        ArgumentNullException.ThrowIfNull(serviceCollection);
 
         serviceCollection.AddMqttConnectionHandler();
         serviceCollection.AddHostedMqttServer(configure);

Source/MQTTnet.AspnetCore/SocketAwaitable.cs

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

Source/MQTTnet.AspnetCore/SocketConnection.cs

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

Source/MQTTnet.Benchmarks/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+[assembly: DoNotParallelize]

Source/MQTTnet.Benchmarks/AsyncLockBenchmark.cs

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

Source/MQTTnet.Benchmarks/BaseBenchmark.cs

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

Source/MQTTnet.Benchmarks/ChannelAdapterBenchmark.cs

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

Source/MQTTnet.Benchmarks/LoggerBenchmark.cs

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

Source/MQTTnet.Benchmarks/MQTTnet.Benchmarks.csproj

@@ -18,7 +18,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="BenchmarkDotNet" Version="0.13.12"/>
+        <PackageReference Include="BenchmarkDotNet" Version="0.15.4" />
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.Benchmarks/MemoryCopyBenchmark.cs

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

Source/MQTTnet.Benchmarks/MessageDeliveryBenchmark.cs

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

Source/MQTTnet.Benchmarks/MessageProcessingMqttConnectionContextBenchmark.cs

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

Source/MQTTnet.Benchmarks/MqttBufferReaderBenchmark.cs

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

Source/MQTTnet.Benchmarks/MqttPacketReaderWriterBenchmark.cs

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

Source/MQTTnet.Benchmarks/MqttTcpChannelBenchmark.cs

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

Source/MQTTnet.Benchmarks/Program.cs

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

Source/MQTTnet.Benchmarks/ReaderExtensionsBenchmark.cs

@@ -1,240 +1,86 @@
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
-using MQTTnet.Adapter;
 using MQTTnet.AspNetCore;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
-using MQTTnet.Packets;
-using System;
 using System.Buffers;
 using System.IO;
 using System.IO.Pipelines;
-using System.Linq;
 using System.Threading.Tasks;
 
-namespace MQTTnet.Benchmarks
-{
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter, RankColumn]
-    [MemoryDiagnoser]
-    public class ReaderExtensionsBenchmark
-    {
-        MqttPacketFormatterAdapter mqttPacketFormatter;
-        MemoryStream stream;
+namespace MQTTnet.Benchmarks;
 
-        [GlobalSetup]
-        public void GlobalSetup()
-        {
-            mqttPacketFormatter = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
-            var mqttMessage = new MqttApplicationMessageBuilder()
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class ReaderExtensionsBenchmark
+{
+    MqttPacketFormatterAdapter _mqttPacketFormatter;
+    MemoryStream _stream;
+
+    [GlobalSetup]
+    public void GlobalSetup()
+    {
+        _mqttPacketFormatter = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
+        var mqttMessage = new MqttApplicationMessageBuilder()
             .WithTopic("topic")
             .WithPayload(new byte[10 * 1024])
             .Build();
 
-            var packet = MqttPublishPacketFactory.Create(mqttMessage);
-
-            var buffer = mqttPacketFormatter.Encode(packet);
-            stream = new MemoryStream();
-            stream.Write(buffer.Packet);
-            stream.Write(buffer.Payload.ToArray());
-            mqttPacketFormatter.Cleanup();
-        }
-
-        [Benchmark(Baseline = true)]
-        public async Task Before()
-        {
-            stream.Position = 0;
-            var input = PipeReader.Create(stream);
-
-            while (true)
-            {
-                ReadResult readResult;
-                var readTask = input.ReadAsync();
-                if (readTask.IsCompleted)
-                {
-                    readResult = readTask.Result;
-                }
-                else
-                {
-                    readResult = await readTask.ConfigureAwait(false);
-                }
-
-                var buffer = readResult.Buffer;
-
-                var consumed = buffer.Start;
-                var observed = buffer.Start;
-
-                try
-                {
-                    if (!buffer.IsEmpty)
-                    {
-                        if (ReaderExtensions_Before.TryDecode(mqttPacketFormatter, buffer, out var packet, out consumed, out observed, out var received))
-                        {
-                            break;
-                        }
-                    }
-                    else if (readResult.IsCompleted)
-                    {
-                        throw new MqttCommunicationException("Connection Aborted");
-                    }
-                }
-                finally
-                {
-                    // The buffer was sliced up to where it was consumed, so we can just advance to the start.
-                    // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
-                    // before yielding the read again.
-                    input.AdvanceTo(consumed, observed);
-                }
-            }
-        }
-
-        [Benchmark]
-        public async Task After()
-        {
-            stream.Position = 0;
-            var input = PipeReader.Create(stream);
-
-            while (true)
-            {
-                ReadResult readResult;
-                var readTask = input.ReadAsync();
-                if (readTask.IsCompleted)
-                {
-                    readResult = readTask.Result;
-                }
-                else
-                {
-                    readResult = await readTask.ConfigureAwait(false);
-                }
-
-                var buffer = readResult.Buffer;
-
-                var consumed = buffer.Start;
-                var observed = buffer.Start;
-
-                try
-                {
-                    if (!buffer.IsEmpty)
-                    {
-                        if (ReaderExtensions.TryDecode(mqttPacketFormatter, buffer, out var packet, out consumed, out observed, out var received))
-                        {
-                            break;
-                        }
-                    }
-                    else if (readResult.IsCompleted)
-                    {
-                        throw new MqttCommunicationException("Connection Aborted");
-                    }
-                }
-                finally
-                {
-                    // The buffer was sliced up to where it was consumed, so we can just advance to the start.
-                    // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
-                    // before yielding the read again.
-                    input.AdvanceTo(consumed, observed);
-                }
-            }
-        }
-
-        public static class ReaderExtensions_Before
-        {
-            public static bool TryDecode(MqttPacketFormatterAdapter formatter,
-                in ReadOnlySequence<byte> input,
-                out MqttPacket packet,
-                out SequencePosition consumed,
-                out SequencePosition observed,
-                out int bytesRead)
-            {
-                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;
-            }
-        }
+        var packet = MqttPublishPacketFactory.Create(mqttMessage);
 
+        var buffer = _mqttPacketFormatter.Encode(packet);
+        _stream = new MemoryStream();
+        _stream.Write(buffer.Packet);
+        _stream.Write(buffer.Payload.ToArray());
+        _mqttPacketFormatter.Cleanup();
     }
-}
+
+    [Benchmark]
+    public async Task After()
+    {
+        _stream.Position = 0;
+        var input = PipeReader.Create(_stream);
+
+        while (true)
+        {
+            ReadResult readResult;
+            var readTask = input.ReadAsync();
+            if (readTask.IsCompleted)
+            {
+                readResult = readTask.Result;
+            }
+            else
+            {
+                readResult = await readTask.ConfigureAwait(false);
+            }
+
+            var buffer = readResult.Buffer;
+
+            var consumed = buffer.Start;
+            var observed = buffer.Start;
+
+            try
+            {
+                if (!buffer.IsEmpty)
+                {
+                    if (_mqttPacketFormatter.TryDecode(buffer, out _, out consumed, out observed, out _))
+                    {
+                        break;
+                    }
+                }
+                else if (readResult.IsCompleted)
+                {
+                    throw new MqttCommunicationException("Connection Aborted");
+                }
+            }
+            finally
+            {
+                // The buffer was sliced up to where it was consumed, so we can just advance to the start.
+                // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
+                // before yielding the read again.
+                input.AdvanceTo(consumed, observed);
+            }
+        }
+    }
+}

Source/MQTTnet.Benchmarks/RoundtripProcessingBenchmark.cs

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

Source/MQTTnet.Benchmarks/SendPacketAsyncBenchmark.cs

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

Source/MQTTnet.Benchmarks/SerializerBenchmark.cs

@@ -15,104 +15,104 @@ using MQTTnet.Formatter.V3;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Diagnostics.Logger;
 using System.Buffers;
+using System.Net;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter]
+[MemoryDiagnoser]
+public class SerializerBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter]
-    [MemoryDiagnoser]
-    public class SerializerBenchmark : BaseBenchmark
+    MqttPacket _packet;
+    ArraySegment<byte> _serializedPacket;
+    IMqttPacketFormatter _serializer;
+    MqttBufferWriter _bufferWriter;
+
+    [GlobalSetup]
+    public void GlobalSetup()
     {
-        MqttPacket _packet;
-        ArraySegment<byte> _serializedPacket;
-        IMqttPacketFormatter _serializer;
-        MqttBufferWriter _bufferWriter;
-
-        [GlobalSetup]
-        public void GlobalSetup()
+        _packet = new MqttPublishPacket
         {
-            _packet = new MqttPublishPacket
-            {
-                Topic = "A"
-            };
+            Topic = "A"
+        };
 
-            _bufferWriter = new MqttBufferWriter(4096, 65535);
-            _serializer = new MqttV3PacketFormatter(_bufferWriter, MqttProtocolVersion.V311);
-            _serializedPacket = _serializer.Encode(_packet).Join();
-        }
+        _bufferWriter = new MqttBufferWriter(4096, 65535);
+        _serializer = new MqttV3PacketFormatter(_bufferWriter, MqttProtocolVersion.V311);
+        _serializedPacket = _serializer.Encode(_packet).Join();
+    }
 
-        [Benchmark]
-        public void Serialize_10000_Messages()
+    [Benchmark]
+    public void Serialize_10000_Messages()
+    {
+        for (var i = 0; i < 10000; i++)
         {
-            for (var i = 0; i < 10000; i++)
-            {
-                _serializer.Encode(_packet);
-                _bufferWriter.Cleanup();
-            }
-        }
-
-        [Benchmark]
-        public void Deserialize_10000_Messages()
-        {
-            var channel = new BenchmarkMqttChannel(_serializedPacket);
-            var reader = new MqttChannelAdapter(channel, new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535)), new MqttNetEventLogger());
-
-            for (var i = 0; i < 10000; i++)
-            {
-                channel.Reset();
-
-                var header = reader.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
-            }
-        }
-
-        class BenchmarkMqttChannel : IMqttChannel
-        {
-            readonly ArraySegment<byte> _buffer;
-            int _position;
-
-            public BenchmarkMqttChannel(ArraySegment<byte> buffer)
-            {
-                _buffer = buffer;
-                _position = _buffer.Offset;
-            }
-
-            public string Endpoint { get; } = string.Empty;
-
-            public bool IsSecureConnection { get; } = false;
-
-            public X509Certificate2 ClientCertificate { get; }
-
-            public void Reset()
-            {
-                _position = _buffer.Offset;
-            }
-
-            public Task ConnectAsync(CancellationToken cancellationToken)
-            {
-                throw new NotSupportedException();
-            }
-
-            public Task DisconnectAsync(CancellationToken cancellationToken)
-            {
-                throw new NotSupportedException();
-            }
-
-            public Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
-            {
-                Array.Copy(_buffer.Array, _position, buffer, offset, count);
-                _position += count;
-
-                return Task.FromResult(count);
-            }
-
-            public Task WriteAsync(ReadOnlySequence<byte> buffer, bool isEndOfPacket, CancellationToken cancellationToken)
-            {
-                throw new NotSupportedException();
-            }
-
-            public void Dispose()
-            {
-            }
+            _serializer.Encode(_packet);
+            _bufferWriter.Cleanup();
         }
     }
-}
+
+    [Benchmark]
+    public void Deserialize_10000_Messages()
+    {
+        var channel = new BenchmarkMqttChannel(_serializedPacket);
+        var reader = new MqttChannelAdapter(channel, new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535)), new MqttNetEventLogger());
+
+        for (var i = 0; i < 10000; i++)
+        {
+            channel.Reset();
+
+            reader.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
+        }
+    }
+
+    class BenchmarkMqttChannel : IMqttChannel
+    {
+        readonly ArraySegment<byte> _buffer;
+        int _position;
+
+        public BenchmarkMqttChannel(ArraySegment<byte> buffer)
+        {
+            _buffer = buffer;
+            _position = _buffer.Offset;
+        }
+
+        public EndPoint RemoteEndPoint { get; set; }
+
+        public bool IsSecureConnection { get; } = false;
+
+        public X509Certificate2 ClientCertificate { get; set; }
+
+        public void Reset()
+        {
+            _position = _buffer.Offset;
+        }
+
+        public Task ConnectAsync(CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public Task DisconnectAsync(CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            Array.Copy(_buffer!.Array!, _position, buffer, offset, count);
+            _position += count;
+
+            return Task.FromResult(count);
+        }
+
+        public Task WriteAsync(ReadOnlySequence<byte> buffer, bool isEndOfPacket, CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}

Source/MQTTnet.Benchmarks/ServerProcessingBenchmark.cs

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

Source/MQTTnet.Benchmarks/SubscribeBenchmark.cs

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

Source/MQTTnet.Benchmarks/TcpPipesBenchmark.cs

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

Source/MQTTnet.Benchmarks/TopicFilterComparerBenchmark.cs

@@ -2,276 +2,32 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter]
+[MemoryDiagnoser]
+public class TopicFilterComparerBenchmark : BaseBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
-    [RPlotExporter]
-    [MemoryDiagnoser]
-    public class TopicFilterComparerBenchmark : BaseBenchmark
+    readonly string _longTopic =
+        "AAAAAAAAAAAAAssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
+
+    [Benchmark]
+    public void MqttTopicFilterComparer_10000_LoopMethod()
     {
-        static readonly char[] TopicLevelSeparator = { '/' };
-
-        readonly string _longTopic =
-            "AAAAAAAAAAAAAssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
-
-        [Benchmark]
-        public void MqttTopicFilterComparer_10000_LoopMethod()
+        for (var i = 0; i < 100000; i++)
         {
-            for (var i = 0; i < 100000; i++)
-            {
-                MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/#");
-                MqttTopicFilterComparer.Compare("sport/tennis/player1/ranking", "sport/#/ranking");
-                MqttTopicFilterComparer.Compare("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
-                MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/tennis/+");
-                MqttTopicFilterComparer.Compare("/finance", "+/+");
-                MqttTopicFilterComparer.Compare("/finance", "/+");
-                MqttTopicFilterComparer.Compare("/finance", "+");
-                MqttTopicFilterComparer.Compare(_longTopic, _longTopic);
-            }
-        }
-
-        [Benchmark]
-        public void MqttTopicFilterComparer_10000_LoopMethod_Without_Pointer()
-        {
-            for (var i = 0; i < 100000; i++)
-            {
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1", "sport/#");
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1/ranking", "sport/#/ranking");
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
-                MqttTopicFilterComparerWithoutPointer.Compare("sport/tennis/player1", "sport/tennis/+");
-                MqttTopicFilterComparerWithoutPointer.Compare("/finance", "+/+");
-                MqttTopicFilterComparerWithoutPointer.Compare("/finance", "/+");
-                MqttTopicFilterComparerWithoutPointer.Compare("/finance", "+");
-                MqttTopicFilterComparerWithoutPointer.Compare(_longTopic, _longTopic);
-            }
-        }
-
-        [Benchmark]
-        public void MqttTopicFilterComparer_10000_StringSplitMethod()
-        {
-            for (var i = 0; i < 100000; i++)
-            {
-                LegacyMethodByStringSplit("sport/tennis/player1", "sport/#");
-                LegacyMethodByStringSplit("sport/tennis/player1/ranking", "sport/#/ranking");
-                LegacyMethodByStringSplit("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
-                LegacyMethodByStringSplit("sport/tennis/player1", "sport/tennis/+");
-                LegacyMethodByStringSplit("/finance", "+/+");
-                LegacyMethodByStringSplit("/finance", "/+");
-                LegacyMethodByStringSplit("/finance", "+");
-                MqttTopicFilterComparer.Compare(_longTopic, _longTopic);
-            }
-        }
-
-        [GlobalSetup]
-        public void Setup()
-        {
-        }
-
-        static bool LegacyMethodByStringSplit(string topic, string filter)
-        {
-            if (topic == null)
-            {
-                throw new ArgumentNullException(nameof(topic));
-            }
-
-            if (filter == null)
-            {
-                throw new ArgumentNullException(nameof(filter));
-            }
-
-            if (string.Equals(topic, filter, StringComparison.Ordinal))
-            {
-                return true;
-            }
-
-            var fragmentsTopic = topic.Split(TopicLevelSeparator, StringSplitOptions.None);
-            var fragmentsFilter = filter.Split(TopicLevelSeparator, StringSplitOptions.None);
-
-            // # > In either case it MUST be the last character specified in the Topic Filter [MQTT-4.7.1-2].
-            for (var i = 0; i < fragmentsFilter.Length; i++)
-            {
-                if (fragmentsFilter[i] == "+")
-                {
-                    continue;
-                }
-
-                if (fragmentsFilter[i] == "#")
-                {
-                    return true;
-                }
-
-                if (i >= fragmentsTopic.Length)
-                {
-                    return false;
-                }
-
-                if (!string.Equals(fragmentsFilter[i], fragmentsTopic[i], StringComparison.Ordinal))
-                {
-                    return false;
-                }
-            }
-
-            return fragmentsTopic.Length == fragmentsFilter.Length;
-        }
-
-        public static class MqttTopicFilterComparerWithoutPointer
-        {
-            public const char LevelSeparator = '/';
-            public const char MultiLevelWildcard = '#';
-            public const char SingleLevelWildcard = '+';
-            public const char ReservedTopicPrefix = '$';
-
-            public static MqttTopicFilterCompareResult Compare(string topic, string filter)
-            {
-                if (string.IsNullOrEmpty(topic))
-                {
-                    return MqttTopicFilterCompareResult.TopicInvalid;
-                }
-
-                if (string.IsNullOrEmpty(filter))
-                {
-                    return MqttTopicFilterCompareResult.FilterInvalid;
-                }
-
-                var filterOffset = 0;
-                var filterLength = filter.Length;
-
-                var topicOffset = 0;
-                var topicLength = topic.Length;
-
-                var topicPointer = topic;
-                var filterPointer = filter;
-
-                var isMultiLevelFilter = filterPointer[filterLength - 1] == MultiLevelWildcard;
-                var isReservedTopic = topicPointer[0] == ReservedTopicPrefix;
-
-                if (isReservedTopic && filterLength == 1 && isMultiLevelFilter)
-                {
-                    // It is not allowed to receive i.e. '$foo/bar' with filter '#'.
-                    return MqttTopicFilterCompareResult.NoMatch;
-                }
-
-                if (isReservedTopic && filterPointer[0] == SingleLevelWildcard)
-                {
-                    // It is not allowed to receive i.e. '$SYS/monitor/Clients' with filter '+/monitor/Clients'.
-                    return MqttTopicFilterCompareResult.NoMatch;
-                }
-
-                if (filterLength == 1 && isMultiLevelFilter)
-                {
-                    // Filter '#' matches basically everything.
-                    return MqttTopicFilterCompareResult.IsMatch;
-                }
-
-                // Go through the filter char by char.
-                while (filterOffset < filterLength && topicOffset < topicLength)
-                {
-                    // Check if the current char is a multi level wildcard. The char is only allowed
-                    // at the very las position.
-                    if (filterPointer[filterOffset] == MultiLevelWildcard && filterOffset != filterLength - 1)
-                    {
-                        return MqttTopicFilterCompareResult.FilterInvalid;
-                    }
-
-                    if (filterPointer[filterOffset] == topicPointer[topicOffset])
-                    {
-                        if (topicOffset == topicLength - 1)
-                        {
-                            // Check for e.g. "foo" matching "foo/#"
-                            if (filterOffset == filterLength - 3 && filterPointer[filterOffset + 1] == LevelSeparator && isMultiLevelFilter)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-
-                            // Check for e.g. "foo/" matching "foo/#"
-                            if (filterOffset == filterLength - 2 && filterPointer[filterOffset] == LevelSeparator && isMultiLevelFilter)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-                        }
-
-                        filterOffset++;
-                        topicOffset++;
-
-                        // Check if the end was reached and i.e. "foo/bar" matches "foo/bar"
-                        if (filterOffset == filterLength && topicOffset == topicLength)
-                        {
-                            return MqttTopicFilterCompareResult.IsMatch;
-                        }
-
-                        var endOfTopic = topicOffset == topicLength;
-
-                        if (endOfTopic && filterOffset == filterLength - 1 && filterPointer[filterOffset] == SingleLevelWildcard)
-                        {
-                            if (filterOffset > 0 && filterPointer[filterOffset - 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            return MqttTopicFilterCompareResult.IsMatch;
-                        }
-                    }
-                    else
-                    {
-                        if (filterPointer[filterOffset] == SingleLevelWildcard)
-                        {
-                            // Check for invalid "+foo" or "a/+foo" subscription
-                            if (filterOffset > 0 && filterPointer[filterOffset - 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            // Check for bad "foo+" or "foo+/a" subscription
-                            if (filterOffset < filterLength - 1 && filterPointer[filterOffset + 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            filterOffset++;
-                            while (topicOffset < topicLength && topicPointer[topicOffset] != LevelSeparator)
-                            {
-                                topicOffset++;
-                            }
-
-                            if (topicOffset == topicLength && filterOffset == filterLength)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-                        }
-                        else if (filterPointer[filterOffset] == MultiLevelWildcard)
-                        {
-                            if (filterOffset > 0 && filterPointer[filterOffset - 1] != LevelSeparator)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            if (filterOffset + 1 != filterLength)
-                            {
-                                return MqttTopicFilterCompareResult.FilterInvalid;
-                            }
-
-                            return MqttTopicFilterCompareResult.IsMatch;
-                        }
-                        else
-                        {
-                            // Check for e.g. "foo/bar" matching "foo/+/#".
-                            if (filterOffset > 0 && filterOffset + 2 == filterLength && topicOffset == topicLength && filterPointer[filterOffset - 1] == SingleLevelWildcard &&
-                                filterPointer[filterOffset] == LevelSeparator && isMultiLevelFilter)
-                            {
-                                return MqttTopicFilterCompareResult.IsMatch;
-                            }
-
-                            return MqttTopicFilterCompareResult.NoMatch;
-                        }
-                    }
-                }
-
-                return MqttTopicFilterCompareResult.NoMatch;
-            }
+            MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/#");
+            MqttTopicFilterComparer.Compare("sport/tennis/player1/ranking", "sport/#/ranking");
+            MqttTopicFilterComparer.Compare("sport/tennis/player1/score/wimbledon", "sport/+/player1/#");
+            MqttTopicFilterComparer.Compare("sport/tennis/player1", "sport/tennis/+");
+            MqttTopicFilterComparer.Compare("/finance", "+/+");
+            MqttTopicFilterComparer.Compare("/finance", "/+");
+            MqttTopicFilterComparer.Compare("/finance", "+");
+            MqttTopicFilterComparer.Compare(_longTopic, _longTopic);
         }
     }
 }

Source/MQTTnet.Benchmarks/TopicGenerator.cs

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

Source/MQTTnet.Benchmarks/UnsubscribeBenchmark.cs

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

Source/MQTTnet.Extensions.Rpc/DefaultMqttRpcClientTopicGenerationStrategy.cs

@@ -4,30 +4,26 @@
 
 using System;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class DefaultMqttRpcClientTopicGenerationStrategy : IMqttRpcClientTopicGenerationStrategy
 {
-    public sealed class DefaultMqttRpcClientTopicGenerationStrategy : IMqttRpcClientTopicGenerationStrategy
+    public MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context)
     {
-        public MqttRpcTopicPair CreateRpcTopics(TopicGenerationContext context)
+        ArgumentNullException.ThrowIfNull(context);
+
+        if (context.MethodName.Contains("/") || context.MethodName.Contains("+") || context.MethodName.Contains("#"))
         {
-            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 #.");
-            }
-            
-            var requestTopic = $"MQTTnet.RPC/{Guid.NewGuid():N}/{context.MethodName}";
-            var responseTopic = requestTopic + "/response";
-
-            return new MqttRpcTopicPair
-            {
-                RequestTopic = requestTopic,
-                ResponseTopic = responseTopic
-            };
+            throw new ArgumentException("The method name cannot contain /, + or #.");
         }
+
+        var requestTopic = $"MQTTnet.RPC/{Guid.NewGuid():N}/{context.MethodName}";
+        var responseTopic = requestTopic + "/response";
+
+        return new MqttRpcTopicPair
+        {
+            RequestTopic = requestTopic,
+            ResponseTopic = responseTopic
+        };
     }
-}
+}

Source/MQTTnet.Extensions.Rpc/IMqttRpcClient.cs

@@ -8,12 +8,16 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public interface IMqttRpcClient : IDisposable
 {
-    public interface IMqttRpcClient : IDisposable
-    {
-        Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string,object> parameters = null);
-        
-        Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default);
-    }
+    Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object>? parameters = null);
+
+    Task<byte[]> ExecuteAsync(
+        string methodName,
+        byte[] payload,
+        MqttQualityOfServiceLevel qualityOfServiceLevel,
+        IDictionary<string, object>? parameters = null,
+        CancellationToken cancellationToken = default);
 }

Source/MQTTnet.Extensions.Rpc/IMqttRpcClientTopicGenerationStrategy.cs

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

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

@@ -26,7 +26,7 @@
         <PackageIcon>nuget.png</PackageIcon>
         <EmbedUntrackedSources>true</EmbedUntrackedSources>
         <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <PackageLicenseExpression>MIT</PackageLicenseExpression>
+        <PackageLicenseFile>LICENSE</PackageLicenseFile>
         <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
         <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
@@ -36,13 +36,14 @@
         <NuGetAudit>true</NuGetAudit>
         <NuGetAuditLevel>low</NuGetAuditLevel>
         <AnalysisLevel>latest-Recommended</AnalysisLevel>
+        <IsAotCompatible>true</IsAotCompatible>
+        <LangVersion>default</LangVersion>
+        <Nullable>enable</Nullable>
     </PropertyGroup>
 
     <ItemGroup>
-        <None Include="..\..\Images\nuget.png">
-            <Pack>True</Pack>
-            <PackagePath>\</PackagePath>
-        </None>
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
+        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.Extensions.Rpc/MqttFactoryExtensions.cs

@@ -4,33 +4,25 @@
 
 using System;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public static class MqttFactoryExtensions
 {
-    public static class MqttFactoryExtensions
+    public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory clientFactory, IMqttClient mqttClient)
     {
-        public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory clientFactory, IMqttClient mqttClient)
-        {
-            return clientFactory.CreateMqttRpcClient(
-                mqttClient,
-                new MqttRpcClientOptions
-                {
-                    TopicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy()
-                });
-        }
-
-        public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory _, IMqttClient mqttClient, MqttRpcClientOptions rpcClientOptions)
-        {
-            if (mqttClient == null)
+        return clientFactory.CreateMqttRpcClient(
+            mqttClient,
+            new MqttRpcClientOptions
             {
-                throw new ArgumentNullException(nameof(mqttClient));
-            }
+                TopicGenerationStrategy = new DefaultMqttRpcClientTopicGenerationStrategy()
+            });
+    }
 
-            if (rpcClientOptions == null)
-            {
-                throw new ArgumentNullException(nameof(rpcClientOptions));
-            }
+    public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory _, IMqttClient mqttClient, MqttRpcClientOptions rpcClientOptions)
+    {
+        ArgumentNullException.ThrowIfNull(mqttClient);
+        ArgumentNullException.ThrowIfNull(rpcClientOptions);
 
-            return new MqttRpcClient(mqttClient, rpcClientOptions);
-        }
+        return new MqttRpcClient(mqttClient, rpcClientOptions);
     }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClient.cs

@@ -6,7 +6,6 @@ using System;
 using System.Buffers;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Exceptions;
@@ -14,131 +13,134 @@ using MQTTnet.Formatter;
 using MQTTnet.Internal;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class MqttRpcClient : IMqttRpcClient
 {
-    public sealed class MqttRpcClient : IMqttRpcClient
+    readonly IMqttClient _mqttClient;
+    readonly MqttRpcClientOptions _options;
+
+    readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new();
+
+    public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
     {
-        readonly IMqttClient _mqttClient;
-        readonly MqttRpcClientOptions _options;
+        _mqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
+        _options = options ?? throw new ArgumentNullException(nameof(options));
 
-        readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>>();
+        _mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
+    }
 
-        public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
+    public void Dispose()
+    {
+        _mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
+
+        foreach (var tcs in _waitingCalls)
         {
-            _mqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
-            _options = options ?? throw new ArgumentNullException(nameof(options));
-
-            _mqttClient.ApplicationMessageReceivedAsync += HandleApplicationMessageReceivedAsync;
+            tcs.Value.TrySetCanceled();
         }
 
-        public void Dispose()
+        _waitingCalls.Clear();
+    }
+
+    public async Task<byte[]> ExecuteAsync(
+        TimeSpan timeout,
+        string methodName,
+        byte[] payload,
+        MqttQualityOfServiceLevel qualityOfServiceLevel,
+        IDictionary<string, object>? parameters = null)
+    {
+        using var timeoutToken = new CancellationTokenSource(timeout);
+        try
         {
-            _mqttClient.ApplicationMessageReceivedAsync -= HandleApplicationMessageReceivedAsync;
-
-            foreach (var tcs in _waitingCalls)
-            {
-                tcs.Value.TrySetCanceled();
-            }
-
-            _waitingCalls.Clear();
+            return await ExecuteAsync(methodName, payload, qualityOfServiceLevel, parameters, timeoutToken.Token).ConfigureAwait(false);
         }
-
-        public async Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null)
+        catch (OperationCanceledException exception)
         {
-            using (var timeoutToken = new CancellationTokenSource(timeout))
+            if (timeoutToken.IsCancellationRequested)
             {
-                try
-                {
-                    return await ExecuteAsync(methodName, payload, qualityOfServiceLevel, parameters, timeoutToken.Token).ConfigureAwait(false);
-                }
-                catch (OperationCanceledException exception)
-                {
-                    if (timeoutToken.IsCancellationRequested)
-                    {
-                        throw new MqttCommunicationTimedOutException(exception);
-                    }
-
-                    throw;
-                }
-            }
-        }
-
-        public async Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default)
-        {
-            if (methodName == null)
-            {
-                throw new ArgumentNullException(nameof(methodName));
+                throw new MqttCommunicationTimedOutException(exception);
             }
 
-            var context = new TopicGenerationContext(_mqttClient, _options, methodName, parameters, qualityOfServiceLevel);
-            var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(context);
-
-            var requestTopic = topicNames.RequestTopic;
-            var responseTopic = topicNames.ResponseTopic;
-
-            if (string.IsNullOrWhiteSpace(requestTopic))
-            {
-                throw new MqttProtocolViolationException("RPC request topic is empty.");
-            }
-
-            if (string.IsNullOrWhiteSpace(responseTopic))
-            {
-                throw new MqttProtocolViolationException("RPC response topic is empty.");
-            }
-
-            var requestMessageBuilder = new MqttApplicationMessageBuilder().WithTopic(requestTopic).WithPayload(payload).WithQualityOfServiceLevel(qualityOfServiceLevel);
-
-            if (_mqttClient.Options.ProtocolVersion == MqttProtocolVersion.V500)
-            {
-                requestMessageBuilder.WithResponseTopic(responseTopic);
-            }
-
-            var requestMessage = requestMessageBuilder.Build();
-
-            try
-            {
-                var awaitable = new AsyncTaskCompletionSource<byte[]>();
-
-                if (!_waitingCalls.TryAdd(responseTopic, awaitable))
-                {
-                    throw new InvalidOperationException();
-                }
-
-                var subscribeOptions = new MqttClientSubscribeOptionsBuilder().WithTopicFilter(responseTopic, qualityOfServiceLevel).Build();
-
-                await _mqttClient.SubscribeAsync(subscribeOptions, cancellationToken).ConfigureAwait(false);
-                await _mqttClient.PublishAsync(requestMessage, cancellationToken).ConfigureAwait(false);
-
-                using (cancellationToken.Register(
-                           () =>
-                           {
-                               awaitable.TrySetCanceled();
-                           }))
-                {
-                    return await awaitable.Task.ConfigureAwait(false);
-                }
-            }
-            finally
-            {
-                _waitingCalls.TryRemove(responseTopic, out _);
-                await _mqttClient.UnsubscribeAsync(responseTopic, CancellationToken.None).ConfigureAwait(false);
-            }
-        }
-
-        Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
-        {
-            if (!_waitingCalls.TryRemove(eventArgs.ApplicationMessage.Topic, out var awaitable))
-            {
-                return CompletedTask.Instance;
-            }
-
-            var payloadBuffer = eventArgs.ApplicationMessage.Payload.ToArray();
-            awaitable.TrySetResult(payloadBuffer);
-
-            // Set this message to handled to that other code can avoid execution etc.
-            eventArgs.IsHandled = true;
-
-            return CompletedTask.Instance;
+            throw;
         }
     }
+
+    public async Task<byte[]> ExecuteAsync(
+        string methodName,
+        byte[] payload,
+        MqttQualityOfServiceLevel qualityOfServiceLevel,
+        IDictionary<string, object>? parameters = null,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(methodName);
+
+        var context = new TopicGenerationContext(_mqttClient, _options, methodName, parameters, qualityOfServiceLevel);
+        var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(context);
+
+        var requestTopic = topicNames.RequestTopic;
+        var responseTopic = topicNames.ResponseTopic;
+
+        if (string.IsNullOrWhiteSpace(requestTopic))
+        {
+            throw new MqttProtocolViolationException("RPC request topic is empty.");
+        }
+
+        if (string.IsNullOrWhiteSpace(responseTopic))
+        {
+            throw new MqttProtocolViolationException("RPC response topic is empty.");
+        }
+
+        var requestMessageBuilder = new MqttApplicationMessageBuilder().WithTopic(requestTopic).WithPayload(payload).WithQualityOfServiceLevel(qualityOfServiceLevel);
+
+        if (_mqttClient.Options!.ProtocolVersion == MqttProtocolVersion.V500)
+        {
+            requestMessageBuilder.WithResponseTopic(responseTopic);
+        }
+
+        var requestMessage = requestMessageBuilder.Build();
+
+        try
+        {
+            var awaitable = new AsyncTaskCompletionSource<byte[]>();
+
+            if (!_waitingCalls.TryAdd(responseTopic, awaitable))
+            {
+                throw new InvalidOperationException();
+            }
+
+            var subscribeOptions = new MqttClientSubscribeOptionsBuilder().WithTopicFilter(responseTopic, qualityOfServiceLevel).Build();
+
+            await _mqttClient.SubscribeAsync(subscribeOptions, cancellationToken).ConfigureAwait(false);
+            await _mqttClient.PublishAsync(requestMessage, cancellationToken).ConfigureAwait(false);
+
+            using (cancellationToken.Register(() =>
+                   {
+                       awaitable.TrySetCanceled();
+                   }))
+            {
+                return await awaitable.Task.ConfigureAwait(false);
+            }
+        }
+        finally
+        {
+            _waitingCalls.TryRemove(responseTopic, out _);
+            await _mqttClient.UnsubscribeAsync(responseTopic, CancellationToken.None).ConfigureAwait(false);
+        }
+    }
+
+    Task HandleApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs eventArgs)
+    {
+        if (!_waitingCalls.TryRemove(eventArgs.ApplicationMessage.Topic, out var awaitable))
+        {
+            return CompletedTask.Instance;
+        }
+
+        var payloadBuffer = eventArgs.ApplicationMessage.Payload.ToArray();
+        awaitable.TrySetResult(payloadBuffer);
+
+        // Set this message to handled to that other code can avoid execution etc.
+        eventArgs.IsHandled = true;
+
+        return CompletedTask.Instance;
+    }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClientExtensions.cs

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

Source/MQTTnet.Extensions.Rpc/MqttRpcClientOptions.cs

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

Source/MQTTnet.Extensions.Rpc/MqttRpcClientOptionsBuilder.cs

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

Source/MQTTnet.Extensions.Rpc/MqttRpcTopicPair.cs

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

Source/MQTTnet.Extensions.Rpc/TopicGenerationContext.cs

@@ -6,37 +6,40 @@ using System;
 using System.Collections.Generic;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class TopicGenerationContext
 {
-    public sealed class TopicGenerationContext
+    public TopicGenerationContext(
+        IMqttClient mqttClient,
+        MqttRpcClientOptions options,
+        string methodName,
+        IDictionary<string, object>? parameters,
+        MqttQualityOfServiceLevel qualityOfServiceLevel)
     {
-        public TopicGenerationContext(IMqttClient mqttClient, MqttRpcClientOptions options, string methodName,
-            IDictionary<string, object> parameters, MqttQualityOfServiceLevel qualityOfServiceLevel)
-        {
-            MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
-            Parameters = parameters;
-            QualityOfServiceLevel = qualityOfServiceLevel;
-            MqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
-            Options = options ?? throw new ArgumentNullException(nameof(options));
-        }
-
-        public string MethodName { get; }
-
-        public IDictionary<string, object> Parameters { get; }
-
-        public IMqttClient MqttClient { get; }
-
-        public MqttRpcClientOptions Options { get; }
-
-        /// <summary>
-        ///     Gets or sets the quality of service level.
-        ///     The Quality of Service (QoS) level is an agreement between the sender of a message and the receiver of a message
-        ///     that defines the guarantee of delivery for a specific message.
-        ///     There are 3 QoS levels in MQTT:
-        ///     - At most once  (0): Message gets delivered no time, once or multiple times.
-        ///     - At least once (1): Message gets delivered at least once (one time or more often).
-        ///     - Exactly once  (2): Message gets delivered exactly once (It's ensured that the message only comes once).
-        /// </summary>
-        public MqttQualityOfServiceLevel QualityOfServiceLevel { get; }
+        MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
+        Parameters = parameters;
+        QualityOfServiceLevel = qualityOfServiceLevel;
+        MqttClient = mqttClient ?? throw new ArgumentNullException(nameof(mqttClient));
+        Options = options ?? throw new ArgumentNullException(nameof(options));
     }
+
+    public string MethodName { get; }
+
+    public IMqttClient MqttClient { get; }
+
+    public MqttRpcClientOptions Options { get; }
+
+    public IDictionary<string, object>? Parameters { get; }
+
+    /// <summary>
+    ///     Gets or sets the quality of service level.
+    ///     The Quality of Service (QoS) level is an agreement between the sender of a message and the receiver of a message
+    ///     that defines the guarantee of delivery for a specific message.
+    ///     There are 3 QoS levels in MQTT:
+    ///     - At most once  (0): Message gets delivered no time, once or multiple times.
+    ///     - At least once (1): Message gets delivered at least once (one time or more often).
+    ///     - Exactly once  (2): Message gets delivered exactly once (It's ensured that the message only comes once).
+    /// </summary>
+    public MqttQualityOfServiceLevel QualityOfServiceLevel { get; }
 }

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

@@ -28,10 +28,13 @@
         <PackageIcon>nuget.png</PackageIcon>
         <EmbedUntrackedSources>true</EmbedUntrackedSources>
         <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <PackageLicenseExpression>MIT</PackageLicenseExpression>
+        <PackageLicenseFile>LICENSE</PackageLicenseFile>
         <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
         <NoWarn>1591;NETSDK1138</NoWarn>
+        <IsAotCompatible>true</IsAotCompatible>
+        <LangVersion>default</LangVersion>
+        <Nullable>enable</Nullable>
     </PropertyGroup>
 
     <ItemGroup>
@@ -39,15 +42,16 @@
             <Pack>True</Pack>
             <PackagePath>\</PackagePath>
         </None>
-        <None Include="..\..\Images\nuget.png">
-            <Pack>True</Pack>
-            <PackagePath>\</PackagePath>
-        </None>
     </ItemGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
-        <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
+        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" />
+        <PackageReference Include="System.ValueTuple" Version="4.6.1" />
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.Extensions.TopicTemplate/MqttTopicTemplate.cs

@@ -41,10 +41,7 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
     /// </exception>
     public MqttTopicTemplate(string topicTemplate)
     {
-        if (topicTemplate == null)
-        {
-            throw new ArgumentNullException(nameof(topicTemplate));
-        }
+        ArgumentNullException.ThrowIfNull(topicTemplate);
 
         MqttTopicValidator.ThrowIfInvalidSubscribe(topicTemplate);
 
@@ -233,7 +230,7 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
             throw new ArgumentException("the topic has to match this template", nameof(topic));
         }
 
-        return parseParameterValuesInternal(topic);
+        return ParseParameterValuesInternal(topic);
     }
 
     /// <summary>
@@ -333,7 +330,7 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
         return parameters.Aggregate(this, (t, p) => t.TrySetParameter(p.parameter, p.value));
     }
 
-    IEnumerable<(string parameter, int index, string value)> parseParameterValuesInternal(string topic)
+    IEnumerable<(string parameter, int index, string value)> ParseParameterValuesInternal(string topic)
     {
         // because we have a match, we know the segment array is at least the template's length
         var segments = topic.Split(MqttTopicFilterComparer.LevelSeparator);

Source/MQTTnet.Server/Disconnecting/MqttServerClientDisconnectOptions.cs

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

Source/MQTTnet.Server/Disconnecting/MqttServerClientDisconnectOptionsBuilder.cs

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

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationOptions.cs

@@ -0,0 +1,16 @@
+// 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 MQTTnet.Packets;
+
+namespace MQTTnet.Server.EnhancedAuthentication;
+
+public sealed class ExchangeEnhancedAuthenticationOptions
+{
+    public byte[]? AuthenticationData { get; set; }
+
+    public string? ReasonString { get; set; }
+
+    public List<MqttUserProperty>? UserProperties { get; set; }
+}

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationOptionsFactory.cs

@@ -0,0 +1,70 @@
+// 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.Text;
+using MQTTnet.Packets;
+
+namespace MQTTnet.Server.EnhancedAuthentication;
+
+public sealed class ExchangeEnhancedAuthenticationOptionsFactory
+{
+    readonly ExchangeEnhancedAuthenticationOptions _options = new();
+
+    public ExchangeEnhancedAuthenticationOptions Build()
+    {
+        return _options;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithAuthenticationData(byte[] authenticationData)
+    {
+        _options.AuthenticationData = authenticationData;
+
+        return this;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithAuthenticationData(string authenticationData)
+    {
+        if (authenticationData == null)
+        {
+            _options.AuthenticationData = null;
+        }
+        else
+        {
+            _options.AuthenticationData = Encoding.UTF8.GetBytes(authenticationData);
+        }
+
+        return this;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithReasonString(string reasonString)
+    {
+        _options.ReasonString = reasonString;
+
+        return this;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithUserProperties(List<MqttUserProperty> userProperties)
+    {
+        _options.UserProperties = userProperties;
+
+        return this;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithUserProperty(string name, string value)
+    {
+        if (name == null)
+        {
+            throw new ArgumentNullException(nameof(name));
+        }
+
+        if (_options.UserProperties == null)
+        {
+            _options.UserProperties = new List<MqttUserProperty>();
+        }
+
+        _options.UserProperties.Add(new MqttUserProperty(name, value));
+
+        return this;
+    }
+}

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationResult.cs

@@ -0,0 +1,12 @@
+using MQTTnet.Packets;
+
+namespace MQTTnet.Server.EnhancedAuthentication;
+
+public sealed class ExchangeEnhancedAuthenticationResult
+{
+    public string? ReasonString { get; init; }
+
+    public List<MqttUserProperty>? UserProperties { get; init; }
+
+    public byte[]? AuthenticationData { get; init; }
+}

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationResultFactory.cs

@@ -0,0 +1,34 @@
+using MQTTnet.Packets;
+
+namespace MQTTnet.Server.EnhancedAuthentication;
+
+public static class ExchangeEnhancedAuthenticationResultFactory
+{
+    public static ExchangeEnhancedAuthenticationResult Create(MqttAuthPacket authPacket)
+    {
+        ArgumentNullException.ThrowIfNull(authPacket);
+
+        return new ExchangeEnhancedAuthenticationResult
+        {
+            AuthenticationData = authPacket.AuthenticationData,
+
+            ReasonString = authPacket.ReasonString,
+            UserProperties = authPacket.UserProperties
+        };
+    }
+
+    public static ExchangeEnhancedAuthenticationResult Create(MqttDisconnectPacket disconnectPacket)
+    {
+        ArgumentNullException.ThrowIfNull(disconnectPacket);
+
+        return new ExchangeEnhancedAuthenticationResult
+        {
+            AuthenticationData = null,
+            ReasonString = disconnectPacket.ReasonString,
+            UserProperties = disconnectPacket.UserProperties
+
+            // SessionExpiryInterval makes no sense because the connection is not yet made!
+            // ServerReferences makes no sense when the client initiated a DISCONNECT!
+        };
+    }
+}

Source/MQTTnet.Server/Events/ApplicationMessageEnqueuedEventArgs.cs

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

Source/MQTTnet.Server/Events/ApplicationMessageNotConsumedEventArgs.cs

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

Source/MQTTnet.Server/Events/ClientAcknowledgedPublishPacketEventArgs.cs

@@ -2,45 +2,49 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientAcknowledgedPublishPacketEventArgs : EventArgs
 {
-    public sealed class ClientAcknowledgedPublishPacketEventArgs : EventArgs
+    public ClientAcknowledgedPublishPacketEventArgs(string clientId, string userName, IDictionary sessionItems, MqttPublishPacket publishPacket, MqttPacketWithIdentifier acknowledgePacket)
     {
-        public ClientAcknowledgedPublishPacketEventArgs(string clientId, IDictionary sessionItems, MqttPublishPacket publishPacket, MqttPacketWithIdentifier acknowledgePacket)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-            PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
-            AcknowledgePacket = acknowledgePacket ?? throw new ArgumentNullException(nameof(acknowledgePacket));
-        }
-        
-        /// <summary>
-        ///     Gets the packet which was used for acknowledge. This can be a PubAck or PubComp packet.
-        /// </summary>
-        public MqttPacketWithIdentifier AcknowledgePacket { get; }
-
-        /// <summary>
-        ///     Gets the ID of the client which acknowledged a PUBLISH packet.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        ///     Gets whether the PUBLISH packet is fully acknowledged. This is the case for PUBACK (QoS 1) and PUBCOMP (QoS 2.
-        /// </summary>
-        public bool IsCompleted => AcknowledgePacket is MqttPubAckPacket || AcknowledgePacket is MqttPubCompPacket;
-
-        /// <summary>
-        ///     Gets the PUBLISH packet which was acknowledged.
-        /// </summary>
-        public MqttPublishPacket PublishPacket { get; }
-
-        /// <summary>
-        ///     Gets the session items which contain custom user data per session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
+        PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
+        AcknowledgePacket = acknowledgePacket ?? throw new ArgumentNullException(nameof(acknowledgePacket));
     }
+
+    /// <summary>
+    ///     Gets the packet which was used for acknowledge. This can be a PubAck or PubComp packet.
+    /// </summary>
+    public MqttPacketWithIdentifier AcknowledgePacket { get; }
+
+    /// <summary>
+    ///     Gets the ID of the client which acknowledged a PUBLISH packet.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets whether the PUBLISH packet is fully acknowledged. This is the case for PUBACK (QoS 1) and PUBCOMP (QoS 2.
+    /// </summary>
+    public bool IsCompleted => AcknowledgePacket is MqttPubAckPacket || AcknowledgePacket is MqttPubCompPacket;
+
+    /// <summary>
+    ///     Gets the PUBLISH packet which was acknowledged.
+    /// </summary>
+    public MqttPublishPacket PublishPacket { get; }
+
+    /// <summary>
+    ///     Gets the session items which contain custom user data per session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/ClientConnectedEventArgs.cs

@@ -2,60 +2,67 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
+using System.Net;
+using System.Text;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientConnectedEventArgs : EventArgs
 {
-    public sealed class ClientConnectedEventArgs : EventArgs
+    readonly MqttConnectPacket _connectPacket;
+
+    public ClientConnectedEventArgs(MqttConnectPacket connectPacket, MqttProtocolVersion protocolVersion, EndPoint remoteEndPoint, IDictionary sessionItems)
     {
-        readonly MqttConnectPacket _connectPacket;
-
-        public ClientConnectedEventArgs(MqttConnectPacket connectPacket, MqttProtocolVersion protocolVersion, string endpoint, IDictionary sessionItems)
-        {
-            _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
-            ProtocolVersion = protocolVersion;
-            Endpoint = endpoint;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        public byte[] AuthenticationData => _connectPacket.AuthenticationData;
-
-        public string AuthenticationMethod => _connectPacket.AuthenticationMethod;
-
-        /// <summary>
-        ///     Gets the client identifier of the connected client.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId => _connectPacket.ClientId;
-
-        /// <summary>
-        ///     Gets the endpoint of the connected client.
-        /// </summary>
-        public string Endpoint { get; }
-
-        /// <summary>
-        ///     Gets the protocol version which is used by the connected client.
-        /// </summary>
-        public MqttProtocolVersion ProtocolVersion { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets the user name of the connected client.
-        /// </summary>
-        public string UserName => _connectPacket.Username;
-
-        /// <summary>
-        ///     Gets the user properties sent by the client.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties => _connectPacket?.UserProperties;
+        _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
+        ProtocolVersion = protocolVersion;
+        RemoteEndPoint = remoteEndPoint;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    public byte[]? AuthenticationData => _connectPacket.AuthenticationData;
+
+    public string? AuthenticationMethod => _connectPacket.AuthenticationMethod;
+
+    /// <summary>
+    ///     Gets the client identifier of the connected client.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId => _connectPacket.ClientId!;
+
+    /// <summary>
+    ///     Gets the endpoint of the connected client.
+    /// </summary>
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string? Endpoint => RemoteEndPoint?.ToString();
+
+    /// <summary>
+    ///     Gets the protocol version which is used by the connected client.
+    /// </summary>
+    public MqttProtocolVersion ProtocolVersion { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the user name of the connected client.
+    /// </summary>
+    public string? UserName => _connectPacket.Username;
+
+    /// <summary>
+    ///     Gets the password of the connected client.
+    /// </summary>
+    public string? Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
+
+    /// <summary>
+    ///     Gets the user properties sent by the client.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty>? UserProperties => _connectPacket?.UserProperties;
 }

Source/MQTTnet.Server/Events/ClientDisconnectedEventArgs.cs

@@ -2,75 +2,88 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
+using System.Net;
+using System.Text;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientDisconnectedEventArgs : EventArgs
 {
-    public sealed class ClientDisconnectedEventArgs : EventArgs
+    readonly MqttConnectPacket _connectPacket;
+    readonly MqttDisconnectPacket _disconnectPacket;
+
+    public ClientDisconnectedEventArgs(
+        MqttConnectPacket connectPacket,
+        MqttDisconnectPacket disconnectPacket,
+        MqttClientDisconnectType disconnectType,
+        EndPoint remoteEndPoint,
+        IDictionary sessionItems)
     {
-        readonly MqttDisconnectPacket _disconnectPacket;
+        DisconnectType = disconnectType;
+        RemoteEndPoint = remoteEndPoint;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
 
-        public ClientDisconnectedEventArgs(
-            string clientId,
-            MqttDisconnectPacket disconnectPacket,
-            MqttClientDisconnectType disconnectType,
-            string endpoint,
-            IDictionary sessionItems)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            DisconnectType = disconnectType;
-            Endpoint = endpoint;
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-
-            // The DISCONNECT packet can be null in case of a non clean disconnect or session takeover.
-            _disconnectPacket = disconnectPacket;
-        }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        public MqttClientDisconnectType DisconnectType { get; }
-
-        public string Endpoint { get; }
-
-        /// <summary>
-        ///     Gets the reason code sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public MqttDisconnectReasonCode? ReasonCode => _disconnectPacket?.ReasonCode;
-
-        /// <summary>
-        ///     Gets the reason string sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public string ReasonString => _disconnectPacket?.ReasonString;
-
-        /// <summary>
-        ///     Gets the session expiry interval sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public uint SessionExpiryInterval => _disconnectPacket?.SessionExpiryInterval ?? 0;
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets the user properties sent by the client.
-        ///     Only available for clean disconnects.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties => _disconnectPacket?.UserProperties;
+        _connectPacket = connectPacket;
+        // The DISCONNECT packet can be null in case of a non clean disconnect or session takeover.
+        _disconnectPacket = disconnectPacket;
     }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId => _connectPacket.ClientId!;
+
+    /// <summary>
+    ///     Gets the user name of the client.
+    /// </summary>
+    public string? UserName => _connectPacket.Username;
+
+    /// <summary>
+    ///     Gets the password of the client.
+    /// </summary>
+    public string? Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
+
+    public MqttClientDisconnectType DisconnectType { get; }
+
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string? Endpoint => RemoteEndPoint?.ToString();
+
+    /// <summary>
+    ///     Gets the reason code sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public MqttDisconnectReasonCode? ReasonCode => _disconnectPacket?.ReasonCode;
+
+    /// <summary>
+    ///     Gets the reason string sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public string? ReasonString => _disconnectPacket?.ReasonString;
+
+    /// <summary>
+    ///     Gets the session expiry interval sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public uint SessionExpiryInterval => _disconnectPacket?.SessionExpiryInterval ?? 0;
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the user properties sent by the client.
+    ///     Only available for clean disconnects.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty>? UserProperties => _disconnectPacket?.UserProperties;
 }

Source/MQTTnet.Server/Events/ClientSubscribedTopicEventArgs.cs

@@ -2,36 +2,40 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientSubscribedTopicEventArgs : EventArgs
 {
-    public sealed class ClientSubscribedTopicEventArgs : EventArgs
+    public ClientSubscribedTopicEventArgs(string clientId, string userName, MqttTopicFilter topicFilter, IDictionary sessionItems)
     {
-        public ClientSubscribedTopicEventArgs(string clientId, MqttTopicFilter topicFilter, IDictionary sessionItems)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets the topic filter.
-        ///     The topic filter can contain topics and wildcards.
-        /// </summary>
-        public MqttTopicFilter TopicFilter { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the topic filter.
+    ///     The topic filter can contain topics and wildcards.
+    /// </summary>
+    public MqttTopicFilter TopicFilter { get; }
 }

Source/MQTTnet.Server/Events/ClientUnsubscribedTopicEventArgs.cs

@@ -2,35 +2,39 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ClientUnsubscribedTopicEventArgs : EventArgs
 {
-    public sealed class ClientUnsubscribedTopicEventArgs : EventArgs
+    public ClientUnsubscribedTopicEventArgs(string clientId, string userName, string topicFilter, IDictionary sessionItems)
     {
-        public ClientUnsubscribedTopicEventArgs(string clientId, string topicFilter, IDictionary sessionItems)
-        {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets or sets the topic filter.
-        ///     The topic filter can contain topics and wildcards.
-        /// </summary>
-        public string TopicFilter { get; }
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets or sets the topic filter.
+    ///     The topic filter can contain topics and wildcards.
+    /// </summary>
+    public string TopicFilter { get; }
 }

Source/MQTTnet.Server/Events/InterceptingClientApplicationMessageEnqueueEventArgs.cs

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

Source/MQTTnet.Server/Events/InterceptingPacketEventArgs.cs

@@ -2,53 +2,60 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Threading;
+using System.Net;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingPacketEventArgs : EventArgs
 {
-    public sealed class InterceptingPacketEventArgs : EventArgs
+    public InterceptingPacketEventArgs(CancellationToken cancellationToken, string clientId, string userName, EndPoint remoteEndPoint, MqttPacket packet, IDictionary sessionItems)
     {
-        public InterceptingPacketEventArgs(CancellationToken cancellationToken, string clientId, string endpoint, MqttPacket packet, IDictionary sessionItems)
-        {
-            CancellationToken = cancellationToken;
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            Endpoint = endpoint;
-            Packet = packet ?? throw new ArgumentNullException(nameof(packet));
-            SessionItems = sessionItems;
-        }
-
-        /// <summary>
-        ///     Gets the cancellation token from the connection managing thread.
-        ///     Use this in further event processing.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client ID which has sent the packet or will receive the packet.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        ///     Gets the endpoint of the sending or receiving client.
-        /// </summary>
-        public string Endpoint { get; }
-
-        /// <summary>
-        ///     Gets or sets the MQTT packet which was received or will be sent.
-        /// </summary>
-        public MqttPacket Packet { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the packet should be processed or not.
-        /// </summary>
-        public bool ProcessPacket { get; set; } = true;
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        CancellationToken = cancellationToken;
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        RemoteEndPoint = remoteEndPoint;
+        Packet = packet ?? throw new ArgumentNullException(nameof(packet));
+        SessionItems = sessionItems;
     }
+
+    /// <summary>
+    ///     Gets the cancellation token from the connection managing thread.
+    ///     Use this in further event processing.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client ID which has sent the packet or will receive the packet.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets the endpoint of the sending or receiving client.
+    /// </summary>
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string Endpoint => RemoteEndPoint?.ToString();
+
+    /// <summary>
+    ///     Gets or sets the MQTT packet which was received or will be sent.
+    /// </summary>
+    public MqttPacket Packet { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the packet should be processed or not.
+    /// </summary>
+    public bool ProcessPacket { get; set; } = true;
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/InterceptingPublishEventArgs.cs

@@ -2,50 +2,53 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Threading;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingPublishEventArgs : EventArgs
 {
-    public sealed class InterceptingPublishEventArgs : EventArgs
+    public InterceptingPublishEventArgs(MqttApplicationMessage applicationMessage, CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems)
     {
-        public InterceptingPublishEventArgs(MqttApplicationMessage applicationMessage, CancellationToken cancellationToken, string clientId, IDictionary sessionItems)
-        {
-            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
-            CancellationToken = cancellationToken;
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        public MqttApplicationMessage ApplicationMessage { get; set; }
-
-        /// <summary>
-        ///     Gets the cancellation token which can indicate that the client connection gets down.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        public bool CloseConnection { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the publish should be processed internally.
-        /// </summary>
-        public bool ProcessPublish { get; set; } = true;
-
-        /// <summary>
-        ///     Gets the response which will be sent to the client via the PUBACK etc. packets.
-        /// </summary>
-        public PublishResponse Response { get; } = new PublishResponse();
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+        CancellationToken = cancellationToken;
+        ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
+        UserName = userName;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    public MqttApplicationMessage ApplicationMessage { get; set; }
+
+    /// <summary>
+    ///     Gets the cancellation token which can indicate that the client connection gets down.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    public bool CloseConnection { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the publish should be processed internally.
+    /// </summary>
+    public bool ProcessPublish { get; set; } = true;
+
+    /// <summary>
+    ///     Gets the response which will be sent to the client via the PUBACK etc. packets.
+    /// </summary>
+    public PublishResponse Response { get; } = new PublishResponse();
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/InterceptingSubscriptionEventArgs.cs

@@ -2,83 +2,86 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingSubscriptionEventArgs : EventArgs
 {
-    public sealed class InterceptingSubscriptionEventArgs : EventArgs
+    public InterceptingSubscriptionEventArgs(
+        CancellationToken cancellationToken,
+        string clientId,
+        string userName,
+        MqttSessionStatus session,
+        MqttTopicFilter topicFilter,
+        List<MqttUserProperty> userProperties)
     {
-        public InterceptingSubscriptionEventArgs(
-            CancellationToken cancellationToken,
-            string clientId,
-            MqttSessionStatus session,
-            MqttTopicFilter topicFilter,
-            List<MqttUserProperty> userProperties)
-        {
-            CancellationToken = cancellationToken;
-            ClientId = clientId;
-            Session = session;
-            TopicFilter = topicFilter;
-            UserProperties = userProperties;
-        }
-
-        /// <summary>
-        ///     Gets the cancellation token which can indicate that the client connection gets down.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should close the client connection.
-        /// </summary>
-        public bool CloseConnection { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should create an internal subscription for the client.
-        ///     The broker can also avoid this and return "success" to the client.
-        ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
-        /// </summary>
-        public bool ProcessSubscription { get; set; } = true;
-
-        /// <summary>
-        ///     Gets or sets the reason string which will be sent to the client in the SUBACK packet.
-        /// </summary>
-        public string ReasonString { get; set; }
-
-        /// <summary>
-        ///     Gets the response which will be sent to the client via the SUBACK packet.
-        /// </summary>
-        public SubscribeResponse Response { get; } = new SubscribeResponse();
-
-        /// <summary>
-        ///     Gets the current client session.
-        /// </summary>
-        public MqttSessionStatus Session { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems => Session.Items;
-
-        /// <summary>
-        ///     Gets or sets the topic filter.
-        ///     The topic filter can contain topics and wildcards.
-        /// </summary>
-        public MqttTopicFilter TopicFilter { get; set; }
-
-        /// <summary>
-        ///     Gets or sets the user properties.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties { get; set; }
+        CancellationToken = cancellationToken;
+        ClientId = clientId;
+        UserName = userName;
+        Session = session;
+        TopicFilter = topicFilter;
+        UserProperties = userProperties;
     }
+
+    /// <summary>
+    ///     Gets the cancellation token which can indicate that the client connection gets down.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should close the client connection.
+    /// </summary>
+    public bool CloseConnection { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should create an internal subscription for the client.
+    ///     The broker can also avoid this and return "success" to the client.
+    ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
+    /// </summary>
+    public bool ProcessSubscription { get; set; } = true;
+
+    /// <summary>
+    ///     Gets or sets the reason string which will be sent to the client in the SUBACK packet.
+    /// </summary>
+    public string ReasonString { get; set; }
+
+    /// <summary>
+    ///     Gets the response which will be sent to the client via the SUBACK packet.
+    /// </summary>
+    public SubscribeResponse Response { get; } = new SubscribeResponse();
+
+    /// <summary>
+    ///     Gets the current client session.
+    /// </summary>
+    public MqttSessionStatus Session { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems => Session.Items;
+
+    /// <summary>
+    ///     Gets or sets the topic filter.
+    ///     The topic filter can contain topics and wildcards.
+    /// </summary>
+    public MqttTopicFilter TopicFilter { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the user properties.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/Events/InterceptingUnsubscriptionEventArgs.cs

@@ -2,71 +2,73 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
 using MQTTnet.Packets;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class InterceptingUnsubscriptionEventArgs : EventArgs
 {
-    public sealed class InterceptingUnsubscriptionEventArgs : EventArgs
+    public InterceptingUnsubscriptionEventArgs(CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems, string topic, List<MqttUserProperty> userProperties)
     {
-        public InterceptingUnsubscriptionEventArgs(CancellationToken cancellationToken, string clientId, IDictionary sessionItems, string topic, List<MqttUserProperty> userProperties)
-        {
-            CancellationToken = cancellationToken;
-            ClientId = clientId;
-            SessionItems = sessionItems;
-            Topic = topic;
-            UserProperties = userProperties;
-        }
-
-        /// <summary>
-        ///     Gets the cancellation token which can indicate that the client connection gets down.
-        /// </summary>
-        public CancellationToken CancellationToken { get; }
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId { get; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should close the client connection.
-        /// </summary>
-        public bool CloseConnection { get; set; }
-
-        /// <summary>
-        ///     Gets or sets whether the broker should remove an internal subscription for the client.
-        ///     The broker can also avoid this and return "success" to the client.
-        ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
-        /// </summary>
-        public bool ProcessUnsubscription { get; set; } = true;
-
-        /// <summary>
-        ///     Gets the response which will be sent to the client via the UNSUBACK pocket.
-        /// </summary>
-        public UnsubscribeResponse Response { get; } = new UnsubscribeResponse();
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets or sets the MQTT topic.
-        ///     In MQTT, the word topic refers to an UTF-8 string that the broker uses to filter messages for each connected
-        ///     client.
-        ///     The topic consists of one or more topic levels. Each topic level is separated by a forward slash (topic level
-        ///     separator).
-        /// </summary>
-        public string Topic { get; }
-
-        /// <summary>
-        ///     Gets or sets the user properties.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties { get; set; }
+        CancellationToken = cancellationToken;
+        ClientId = clientId;
+        UserName = userName;
+        SessionItems = sessionItems;
+        Topic = topic;
+        UserProperties = userProperties;
     }
+
+    /// <summary>
+    ///     Gets the cancellation token which can indicate that the client connection gets down.
+    /// </summary>
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should close the client connection.
+    /// </summary>
+    public bool CloseConnection { get; set; }
+
+    /// <summary>
+    ///     Gets or sets whether the broker should remove an internal subscription for the client.
+    ///     The broker can also avoid this and return "success" to the client.
+    ///     This feature allows using the MQTT Broker as the Frontend and another system as the backend.
+    /// </summary>
+    public bool ProcessUnsubscription { get; set; } = true;
+
+    /// <summary>
+    ///     Gets the response which will be sent to the client via the UNSUBACK pocket.
+    /// </summary>
+    public UnsubscribeResponse Response { get; } = new UnsubscribeResponse();
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets or sets the MQTT topic.
+    ///     In MQTT, the word topic refers to an UTF-8 string that the broker uses to filter messages for each connected
+    ///     client.
+    ///     The topic consists of one or more topic levels. Each topic level is separated by a forward slash (topic level
+    ///     separator).
+    /// </summary>
+    public string Topic { get; }
+
+    /// <summary>
+    ///     Gets or sets the user properties.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/Events/LoadingRetainedMessagesEventArgs.cs

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

Source/MQTTnet.Server/Events/PreparingSessionEventArgs.cs

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

Source/MQTTnet.Server/Events/QueueMessageOverwrittenEventArgs.cs

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

Source/MQTTnet.Server/Events/RetainedMessageChangedEventArgs.cs

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

Source/MQTTnet.Server/Events/SessionDeletedEventArgs.cs

@@ -2,27 +2,31 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class SessionDeletedEventArgs : EventArgs
 {
-    public sealed class SessionDeletedEventArgs : EventArgs
+    public SessionDeletedEventArgs(string id, string userName, IDictionary sessionItems)
     {
-        public SessionDeletedEventArgs(string id, IDictionary sessionItems)
-        {
-            Id = id ?? throw new ArgumentNullException(nameof(id));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
-        }
-
-        /// <summary>
-        ///     Gets the ID of the session.
-        /// </summary>
-        public string Id { get; }
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
+        Id = id ?? throw new ArgumentNullException(nameof(id));
+        UserName = userName;
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
+
+    /// <summary>
+    ///     Gets the ID of the session.
+    /// </summary>
+    public string Id { get; }
+
+    /// <summary>
+    /// Gets the user name of the session.
+    /// </summary>
+    public string UserName { get; }
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
 }

Source/MQTTnet.Server/Events/ValidatingConnectionEventArgs.cs

@@ -2,189 +2,243 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections;
-using System.Collections.Generic;
+using System.Net;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
 using MQTTnet.Adapter;
+using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using MQTTnet.Internal;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
+using MQTTnet.Server.EnhancedAuthentication;
 
-namespace MQTTnet.Server
+namespace MQTTnet.Server;
+
+public sealed class ValidatingConnectionEventArgs : EventArgs
 {
-    public sealed class ValidatingConnectionEventArgs : EventArgs
-    {
-        readonly MqttConnectPacket _connectPacket;
+    readonly MqttConnectPacket _connectPacket;
 
-        public ValidatingConnectionEventArgs(MqttConnectPacket connectPacket, IMqttChannelAdapter clientAdapter, IDictionary sessionItems)
+    public ValidatingConnectionEventArgs(MqttConnectPacket connectPacket, IMqttChannelAdapter clientAdapter, IDictionary sessionItems, CancellationToken cancellationToken)
+    {
+        _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
+        ChannelAdapter = clientAdapter ?? throw new ArgumentNullException(nameof(clientAdapter));
+        SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
+        CancellationToken = cancellationToken;
+    }
+
+    /// <summary>
+    ///     Gets or sets the assigned client identifier.
+    ///     MQTTv5 only.
+    /// </summary>
+    public string AssignedClientIdentifier { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the authentication data.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public byte[] AuthenticationData => _connectPacket.AuthenticationData;
+
+    /// <summary>
+    ///     Gets or sets the authentication method.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public string AuthenticationMethod => _connectPacket.AuthenticationMethod;
+
+    public CancellationToken CancellationToken { get; }
+
+    /// <summary>
+    ///     Gets the channel adapter. This can be a _MqttConnectionContext_ (used in ASP.NET), a _MqttChannelAdapter_ (used for
+    ///     TCP or WebSockets) or a custom implementation.
+    /// </summary>
+    public IMqttChannelAdapter ChannelAdapter { get; }
+
+    /// <summary>
+    ///     Gets or sets a value indicating whether clean sessions are used or not.
+    ///     When a client connects to a broker it can connect using either a non persistent connection (clean session) or a
+    ///     persistent connection.
+    ///     With a non persistent connection the broker doesn't store any subscription information or undelivered messages for
+    ///     the client.
+    ///     This mode is ideal when the client only publishes messages.
+    ///     It can also connect as a durable client using a persistent connection.
+    ///     In this mode, the broker will store subscription information, and undelivered messages for the client.
+    /// </summary>
+    public bool? CleanSession => _connectPacket.CleanSession;
+
+    public X509Certificate2 ClientCertificate => ChannelAdapter.ClientCertificate;
+
+    /// <summary>
+    ///     Gets the client identifier.
+    ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
+    /// </summary>
+    public string ClientId => _connectPacket.ClientId;
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string Endpoint => RemoteEndPoint?.ToString();
+
+    public bool IsSecureConnection => ChannelAdapter.IsSecureConnection;
+
+    /// <summary>
+    ///     Gets or sets the keep alive period.
+    ///     The connection is normally left open by the client so that is can send and receive data at any time.
+    ///     If no data flows over an open connection for a certain time period then the client will generate a PINGREQ and
+    ///     expect to receive a PINGRESP from the broker.
+    ///     This message exchange confirms that the connection is open and working.
+    ///     This period is known as the keep alive period.
+    /// </summary>
+    public ushort? KeepAlivePeriod => _connectPacket.KeepAlivePeriod;
+
+    /// <summary>
+    ///     A value of 0 indicates that the value is not used.
+    /// </summary>
+    public uint MaximumPacketSize => _connectPacket.MaximumPacketSize;
+
+    public string Password => Encoding.UTF8.GetString(RawPassword ?? EmptyBuffer.Array);
+
+    public MqttProtocolVersion ProtocolVersion => ChannelAdapter.PacketFormatterAdapter.ProtocolVersion;
+
+    public byte[] RawPassword => _connectPacket.Password;
+
+    /// <summary>
+    ///     Gets or sets the reason code. When a MQTTv3 client connects the enum value must be one which is
+    ///     also supported in MQTTv3. Otherwise the connection attempt will fail because not all codes can be
+    ///     converted properly.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public MqttConnectReasonCode ReasonCode { get; set; } = MqttConnectReasonCode.Success;
+
+    public string ReasonString { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the receive maximum.
+    ///     This gives the maximum length of the received messages.
+    ///     A value of 0 indicates that the value is not used.
+    /// </summary>
+    public ushort ReceiveMaximum => _connectPacket.ReceiveMaximum;
+
+    public EndPoint RemoteEndPoint => ChannelAdapter.RemoteEndPoint;
+
+    /// <summary>
+    ///     Gets the request problem information.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public bool RequestProblemInformation => _connectPacket.RequestProblemInformation;
+
+    /// <summary>
+    ///     Gets the request response information.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public bool RequestResponseInformation => _connectPacket.RequestResponseInformation;
+
+    /// <summary>
+    ///     Gets or sets the response authentication data.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public byte[] ResponseAuthenticationData { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the response user properties.
+    ///     In MQTT 5, user properties are basic UTF-8 string key-value pairs that you can append to almost every type of MQTT
+    ///     packet.
+    ///     As long as you don’t exceed the maximum message size, you can use an unlimited number of user properties to add
+    ///     metadata to MQTT messages and pass information between publisher, broker, and subscriber.
+    ///     The feature is very similar to the HTTP header concept.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> ResponseUserProperties { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the server reference. This can be used together with i.e. "Server Moved" to send
+    ///     a different server address to the client.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public string ServerReference { get; set; }
+
+    /// <summary>
+    ///     Gets the session expiry interval.
+    ///     The time after a session expires when it's not actively used.
+    ///     A value of 0 means no expiation.
+    /// </summary>
+    public uint SessionExpiryInterval => _connectPacket.SessionExpiryInterval;
+
+    /// <summary>
+    ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
+    /// </summary>
+    public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets or sets the topic alias maximum.
+    ///     This gives the maximum length of the topic alias.
+    ///     A value of 0 indicates that the value is not used.
+    /// </summary>
+    public ushort TopicAliasMaximum => _connectPacket.TopicAliasMaximum;
+
+    public string UserName => _connectPacket.Username;
+
+    /// <summary>
+    ///     Gets or sets the user properties.
+    ///     In MQTT 5, user properties are basic UTF-8 string key-value pairs that you can append to almost every type of MQTT
+    ///     packet.
+    ///     As long as you don’t exceed the maximum message size, you can use an unlimited number of user properties to add
+    ///     metadata to MQTT messages and pass information between publisher, broker, and subscriber.
+    ///     The feature is very similar to the HTTP header concept.
+    ///     <remarks>MQTT 5.0.0+ feature.</remarks>
+    /// </summary>
+    public List<MqttUserProperty> UserProperties => _connectPacket.UserProperties;
+
+    /// <summary>
+    ///     Gets or sets the delay interval for the will message.
+    ///     This is the time between the client disconnect and the time the will message will be sent.
+    ///     A value of 0 indicates that the value is not used.
+    /// </summary>
+    public uint WillDelayInterval => _connectPacket.WillDelayInterval;
+
+    public async Task<ExchangeEnhancedAuthenticationResult> ExchangeEnhancedAuthenticationAsync(
+        ExchangeEnhancedAuthenticationOptions options,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+
+        var requestAuthPacket = new MqttAuthPacket
         {
-            _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
-            ChannelAdapter = clientAdapter ?? throw new ArgumentNullException(nameof(clientAdapter));
-            SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
+            // From RFC: If the initial CONNECT packet included an Authentication Method property then all AUTH packets,
+            // and any successful CONNACK packet MUST include an Authentication Method Property with the same value as in the CONNECT packet [MQTT-4.12.0-5].
+            AuthenticationMethod = AuthenticationMethod,
+
+            // The reason code will stay at continue all the time when connecting. The server will respond with the
+            // CONNACK packet when authentication is done!
+            ReasonCode = MqttAuthenticateReasonCode.ContinueAuthentication,
+
+            AuthenticationData = options.AuthenticationData,
+            ReasonString = options.ReasonString,
+            UserProperties = options.UserProperties
+        };
+
+        await ChannelAdapter.SendPacketAsync(requestAuthPacket, cancellationToken).ConfigureAwait(false);
+
+        var responsePacket = await ChannelAdapter.ReceivePacketAsync(cancellationToken).ConfigureAwait(false);
+
+        if (responsePacket == null)
+        {
+            throw new MqttCommunicationException("The client closed the connection.");
         }
 
-        /// <summary>
-        ///     Gets or sets the assigned client identifier.
-        ///     MQTTv5 only.
-        /// </summary>
-        public string AssignedClientIdentifier { get; set; }
+        if (responsePacket is MqttAuthPacket responseAuthPacket)
+        {
+            if (!string.Equals(AuthenticationMethod, responseAuthPacket.AuthenticationMethod, StringComparison.Ordinal))
+            {
+                throw new MqttProtocolViolationException("The authentication method cannot change while authenticating the client.");
+            }
 
-        /// <summary>
-        ///     Gets or sets the authentication data.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public byte[] AuthenticationData => _connectPacket.AuthenticationData;
+            return ExchangeEnhancedAuthenticationResultFactory.Create(responseAuthPacket);
+        }
 
-        /// <summary>
-        ///     Gets or sets the authentication method.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public string AuthenticationMethod => _connectPacket.AuthenticationMethod;
+        if (responsePacket is MqttDisconnectPacket disconnectPacket)
+        {
+            return ExchangeEnhancedAuthenticationResultFactory.Create(disconnectPacket);
+        }
 
-        /// <summary>
-        ///     Gets the channel adapter. This can be a _MqttConnectionContext_ (used in ASP.NET), a _MqttChannelAdapter_ (used for
-        ///     TCP or WebSockets) or a custom implementation.
-        /// </summary>
-        public IMqttChannelAdapter ChannelAdapter { get; }
-
-        /// <summary>
-        ///     Gets or sets a value indicating whether clean sessions are used or not.
-        ///     When a client connects to a broker it can connect using either a non persistent connection (clean session) or a
-        ///     persistent connection.
-        ///     With a non persistent connection the broker doesn't store any subscription information or undelivered messages for
-        ///     the client.
-        ///     This mode is ideal when the client only publishes messages.
-        ///     It can also connect as a durable client using a persistent connection.
-        ///     In this mode, the broker will store subscription information, and undelivered messages for the client.
-        /// </summary>
-        public bool? CleanSession => _connectPacket.CleanSession;
-
-        public X509Certificate2 ClientCertificate => ChannelAdapter.ClientCertificate;
-
-        /// <summary>
-        ///     Gets the client identifier.
-        ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
-        /// </summary>
-        public string ClientId => _connectPacket.ClientId;
-
-        public string Endpoint => ChannelAdapter.Endpoint;
-
-        public bool IsSecureConnection => ChannelAdapter.IsSecureConnection;
-
-        /// <summary>
-        ///     Gets or sets the keep alive period.
-        ///     The connection is normally left open by the client so that is can send and receive data at any time.
-        ///     If no data flows over an open connection for a certain time period then the client will generate a PINGREQ and
-        ///     expect to receive a PINGRESP from the broker.
-        ///     This message exchange confirms that the connection is open and working.
-        ///     This period is known as the keep alive period.
-        /// </summary>
-        public ushort? KeepAlivePeriod => _connectPacket.KeepAlivePeriod;
-
-        /// <summary>
-        ///     A value of 0 indicates that the value is not used.
-        /// </summary>
-        public uint MaximumPacketSize => _connectPacket.MaximumPacketSize;
-
-        public string Password => Encoding.UTF8.GetString(RawPassword ?? EmptyBuffer.Array);
-
-        public MqttProtocolVersion ProtocolVersion => ChannelAdapter.PacketFormatterAdapter.ProtocolVersion;
-
-        public byte[] RawPassword => _connectPacket.Password;
-
-        /// <summary>
-        ///     Gets or sets the reason code. When a MQTTv3 client connects the enum value must be one which is
-        ///     also supported in MQTTv3. Otherwise the connection attempt will fail because not all codes can be
-        ///     converted properly.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public MqttConnectReasonCode ReasonCode { get; set; } = MqttConnectReasonCode.Success;
-
-        public string ReasonString { get; set; }
-
-        /// <summary>
-        ///     Gets or sets the receive maximum.
-        ///     This gives the maximum length of the receive messages.
-        ///     A value of 0 indicates that the value is not used.
-        /// </summary>
-        public ushort ReceiveMaximum => _connectPacket.ReceiveMaximum;
-
-        /// <summary>
-        ///     Gets the request problem information.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public bool RequestProblemInformation => _connectPacket.RequestProblemInformation;
-
-        /// <summary>
-        ///     Gets the request response information.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public bool RequestResponseInformation => _connectPacket.RequestResponseInformation;
-
-        /// <summary>
-        ///     Gets or sets the response authentication data.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public byte[] ResponseAuthenticationData { get; set; }
-
-        /// <summary>
-        ///     Gets or sets the response user properties.
-        ///     In MQTT 5, user properties are basic UTF-8 string key-value pairs that you can append to almost every type of MQTT
-        ///     packet.
-        ///     As long as you don’t exceed the maximum message size, you can use an unlimited number of user properties to add
-        ///     metadata to MQTT messages and pass information between publisher, broker, and subscriber.
-        ///     The feature is very similar to the HTTP header concept.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> ResponseUserProperties { get; set; }
-
-        /// <summary>
-        ///     Gets or sets the server reference. This can be used together with i.e. "Server Moved" to send
-        ///     a different server address to the client.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public string ServerReference { get; set; }
-
-        /// <summary>
-        ///     Gets the session expiry interval.
-        ///     The time after a session expires when it's not actively used.
-        ///     A value of 0 means no expiation.
-        /// </summary>
-        public uint SessionExpiryInterval => _connectPacket.SessionExpiryInterval;
-
-        /// <summary>
-        ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
-        /// </summary>
-        public IDictionary SessionItems { get; }
-
-        /// <summary>
-        ///     Gets or sets the topic alias maximum.
-        ///     This gives the maximum length of the topic alias.
-        ///     A value of 0 indicates that the value is not used.
-        /// </summary>
-        public ushort TopicAliasMaximum => _connectPacket.TopicAliasMaximum;
-
-        public string UserName => _connectPacket.Username;
-
-        /// <summary>
-        ///     Gets or sets the user properties.
-        ///     In MQTT 5, user properties are basic UTF-8 string key-value pairs that you can append to almost every type of MQTT
-        ///     packet.
-        ///     As long as you don’t exceed the maximum message size, you can use an unlimited number of user properties to add
-        ///     metadata to MQTT messages and pass information between publisher, broker, and subscriber.
-        ///     The feature is very similar to the HTTP header concept.
-        ///     <remarks>MQTT 5.0.0+ feature.</remarks>
-        /// </summary>
-        public List<MqttUserProperty> UserProperties => _connectPacket.UserProperties;
-
-        /// <summary>
-        ///     Gets or sets the will delay interval.
-        ///     This is the time between the client disconnect and the time the will message will be sent.
-        ///     A value of 0 indicates that the value is not used.
-        /// </summary>
-        public uint WillDelayInterval => _connectPacket.WillDelayInterval;
+        throw new MqttProtocolViolationException("Received other packet than AUTH while authenticating.");
     }
 }

Source/MQTTnet.Server/Exceptions/MqttPendingMessagesOverflowException.cs

@@ -0,0 +1,19 @@
+// 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.Server.Exceptions;
+
+public class MqttPendingMessagesOverflowException : Exception
+{
+    public MqttPendingMessagesOverflowException(string sessionId, MqttPendingMessagesOverflowStrategy overflowStrategy) : base(
+        $"Send buffer max pending messages overflow occurred for session '{sessionId}'. Strategy: {overflowStrategy}.")
+    {
+        SessionId = sessionId;
+        OverflowStrategy = overflowStrategy;
+    }
+
+    public MqttPendingMessagesOverflowStrategy OverflowStrategy { get; }
+
+    public string SessionId { get; }
+}

Source/MQTTnet.Server/InjectedMqttApplicationMessage.cs

@@ -23,4 +23,6 @@ public sealed class InjectedMqttApplicationMessage
     public IDictionary CustomSessionItems { get; set; }
 
     public string SenderClientId { get; set; } = string.Empty;
+
+    public string SenderUserName { get; set; }
 }

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

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

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

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

Source/MQTTnet.Server/Internal/CheckSubscriptionsResult.cs

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

Source/MQTTnet.Server/Internal/DispatchApplicationMessageResult.cs

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

Source/MQTTnet.Server/Internal/EnqueueDataPacketResult.cs

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

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

@@ -12,10 +12,7 @@ public static class MqttConnAckPacketFactory
 {
     public static MqttConnAckPacket Create(ValidatingConnectionEventArgs validatingConnectionEventArgs)
     {
-        if (validatingConnectionEventArgs == null)
-        {
-            throw new ArgumentNullException(nameof(validatingConnectionEventArgs));
-        }
+        ArgumentNullException.ThrowIfNull(validatingConnectionEventArgs);
 
         var connAckPacket = new MqttConnAckPacket
         {

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

@@ -11,15 +11,8 @@ public static class MqttPubAckPacketFactory
 {
     public static MqttPubAckPacket Create(MqttPublishPacket publishPacket, DispatchApplicationMessageResult dispatchApplicationMessageResult)
     {
-        if (publishPacket == null)
-        {
-            throw new ArgumentNullException(nameof(publishPacket));
-        }
-
-        if (dispatchApplicationMessageResult == null)
-        {
-            throw new ArgumentNullException(nameof(dispatchApplicationMessageResult));
-        }
+        ArgumentNullException.ThrowIfNull(publishPacket);
+        ArgumentNullException.ThrowIfNull(dispatchApplicationMessageResult);
 
         var pubAckPacket = new MqttPubAckPacket
         {

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

@@ -11,10 +11,7 @@ public static class MqttPubCompPacketFactory
 {
     public static MqttPubCompPacket Create(MqttPubRelPacket pubRelPacket, MqttApplicationMessageReceivedReasonCode reasonCode)
     {
-        if (pubRelPacket == null)
-        {
-            throw new ArgumentNullException(nameof(pubRelPacket));
-        }
+        ArgumentNullException.ThrowIfNull(pubRelPacket);
 
         return new MqttPubCompPacket
         {