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.${{github.run_number}}"
+  VERSION: "5.1.0.${{github.run_number}}"
-  PACKAGE_SUFFIX: "-RC"
+  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

@@ -8,26 +8,56 @@
 
 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
 {
+    const string mosquitto_org = @"
+-----BEGIN CERTIFICATE-----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+-----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 afterwards.
+         * to the server and close the connection afterward.
          *
          * See sample _Connect_Client_ for more details.
          */
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
@@ -35,9 +65,8 @@ public static class Client_Connection_Samples
         // 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()
+    public static async Task Connect()
     {
         /*
          * This sample creates a simple MQTT client and connects to a public broker.
@@ -48,8 +77,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         // Use builder classes where possible in this project.
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
@@ -68,37 +96,74 @@ public static class Client_Connection_Samples
 
         await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
     }
-    }
 
-    public static async Task Connect_Client_Timeout()
+    public static async Task Connect_Using_Enhanced_Authentication()
     {
         /*
-         * This sample creates a simple MQTT client and connects to an invalid broker using a timeout.
+         * This sample uses enhanced authentication (Kerberos) when creating the 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())
+        /*
-        {
+         * Server part...
-            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();
+         */
 
-            try
+        var mqttServerFactory = new MqttServerFactory();
+
+        var serverOptions = mqttServerFactory.CreateServerOptionsBuilder().WithDefaultEndpoint().Build();
+        var server = mqttServerFactory.CreateMqttServer(serverOptions);
+
+        server.ValidatingConnectionAsync += async args =>
         {
-                using (var timeoutToken = new CancellationTokenSource(TimeSpan.FromSeconds(1)))
+            if (args.AuthenticationMethod == "GS2-KRB5")
             {
-                    await mqttClient.ConnectAsync(mqttClientOptions, timeoutToken.Token);
+                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
-            catch (OperationCanceledException)
             {
-                Console.WriteLine("Timeout while connecting.");
+                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_Client_Using_MQTTv5()
+    public static async Task Connect_Using_MQTTv5()
     {
         /*
          * This sample creates a simple MQTT client and connects to a public broker using MQTTv5.
@@ -108,8 +173,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        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.
@@ -119,9 +183,8 @@ public static class Client_Connection_Samples
 
         response.DumpToConsole();
     }
-    }
 
-    public static async Task Connect_Client_Using_TLS_1_2()
+    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.
@@ -131,8 +194,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io")
             .WithTlsOptions(
                 o =>
@@ -146,38 +208,13 @@ public static class Client_Connection_Samples
                 })
             .Build();
 
-            using (var timeout = new CancellationTokenSource(5000))
+        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()
+    public static async Task Connect_Using_TLS_Encryption()
-    {
-        /*
-         * 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.
@@ -187,8 +224,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883)
             .WithTlsOptions(
                 o => o.WithCertificateValidationHandler(
@@ -198,15 +234,48 @@ public static class Client_Connection_Samples
             .Build();
 
         // In MQTTv5 the response contains much more information.
-            using (var timeout = new CancellationTokenSource(5000))
+        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()
@@ -219,8 +288,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("amazon.web.services.broker")
             // Disabling packet fragmentation is very important!
             .WithoutPacketFragmentation()
@@ -232,7 +300,6 @@ public static class Client_Connection_Samples
 
         await mqttClient.DisconnectAsync();
     }
-    }
 
     public static async Task Disconnect_Clean()
     {
@@ -244,8 +311,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
@@ -254,13 +320,12 @@ public static class Client_Connection_Samples
         // 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
+         * This way of disconnecting is treated as a non-clean disconnect which will
          * trigger sending the last will etc.
          */
 
@@ -286,8 +351,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io", 8883)
             .WithTlsOptions(
                 o =>
@@ -306,12 +370,9 @@ public static class Client_Connection_Samples
             .Build();
 
         // In MQTTv5 the response contains much more information.
-            using (var timeout = new CancellationTokenSource(5000))
+        using var timeout = new CancellationTokenSource(5000);
-            {
         await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
     }
-        }
-    }
 
     public static async Task Ping_Server()
     {
@@ -323,8 +384,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
@@ -334,20 +394,18 @@ public static class Client_Connection_Samples
 
         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).
+         * This approach has a risk of deadlocks! Consider using the timer approach (see sample).
          */
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
         mqttClient.DisconnectedAsync += async e =>
@@ -355,13 +413,12 @@ public static class Client_Connection_Samples
             if (e.ClientWasConnected)
             {
                 // Use the current options as the new options.
-                    await mqttClient.ConnectAsync(mqttClient.Options);
+                await mqttClient.ConnectAsync(mqttClientOptions);
             }
         };
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
     }
-    }
 
     public static void Reconnect_Using_Timer()
     {
@@ -373,8 +430,7 @@ public static class Client_Connection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
 
         _ = Task.Run(
@@ -409,55 +465,58 @@ public static class Client_Connection_Samples
         Console.WriteLine("Press <Enter> to exit");
         Console.ReadLine();
     }
-    }
 
-    public static async Task ConnectTls_WithCaFile()
+    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();
 
-        X509Certificate2Collection caChain = new X509Certificate2Collection();
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        caChain.ImportFromPem(mosquitto_org); // from https://test.mosquitto.org/ssl/mosquitto.org.crt
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        try
         {
-            var mqttClientOptions = new MqttClientOptionsBuilder()
+            using var timeoutToken = new CancellationTokenSource(TimeSpan.FromSeconds(1));
-                .WithTcpServer("test.mosquitto.org", 8883)
+            await mqttClient.ConnectAsync(mqttClientOptions, timeoutToken.Token);
-                .WithTlsOptions(new MqttClientTlsOptionsBuilder()
+        }
-                    .WithTrustChain(caChain)
+        catch (OperationCanceledException)
-                    .Build())
+        {
-                .Build();
+            Console.WriteLine("Timeout while connecting.");
-
+        }
-            var connAck = await mqttClient.ConnectAsync(mqttClientOptions);
-            Console.WriteLine("Connected to test.moquitto.org:8883 with CaFile mosquitto.org.crt: " + connAck.ResultCode);
     }
 
-
+    class SampleClientKerberosAuthenticationHandler : IMqttEnhancedAuthenticationHandler
+    {
+        public async Task HandleEnhancedAuthenticationAsync(MqttEnhancedAuthenticationEventArgs eventArgs)
+        {
+            if (eventArgs.AuthenticationMethod != "GS2-KRB5")
+            {
+                throw new InvalidOperationException("Wrong authentication method");
             }
-    const string mosquitto_org = @"
------BEGIN CERTIFICATE-----
-MIIEAzCCAuugAwIBAgIUBY1hlCGvdj4NhBXkZ/uLUZNILAwwDQYJKoZIhvcNAQEL
-BQAwgZAxCzAJBgNVBAYTAkdCMRcwFQYDVQQIDA5Vbml0ZWQgS2luZ2RvbTEOMAwG
-A1UEBwwFRGVyYnkxEjAQBgNVBAoMCU1vc3F1aXR0bzELMAkGA1UECwwCQ0ExFjAU
-BgNVBAMMDW1vc3F1aXR0by5vcmcxHzAdBgkqhkiG9w0BCQEWEHJvZ2VyQGF0Y2hv
-by5vcmcwHhcNMjAwNjA5MTEwNjM5WhcNMzAwNjA3MTEwNjM5WjCBkDELMAkGA1UE
-BhMCR0IxFzAVBgNVBAgMDlVuaXRlZCBLaW5nZG9tMQ4wDAYDVQQHDAVEZXJieTES
-MBAGA1UECgwJTW9zcXVpdHRvMQswCQYDVQQLDAJDQTEWMBQGA1UEAwwNbW9zcXVp
-dHRvLm9yZzEfMB0GCSqGSIb3DQEJARYQcm9nZXJAYXRjaG9vLm9yZzCCASIwDQYJ
-KoZIhvcNAQEBBQADggEPADCCAQoCggEBAME0HKmIzfTOwkKLT3THHe+ObdizamPg
-UZmD64Tf3zJdNeYGYn4CEXbyP6fy3tWc8S2boW6dzrH8SdFf9uo320GJA9B7U1FW
-Te3xda/Lm3JFfaHjkWw7jBwcauQZjpGINHapHRlpiCZsquAthOgxW9SgDgYlGzEA
-s06pkEFiMw+qDfLo/sxFKB6vQlFekMeCymjLCbNwPJyqyhFmPWwio/PDMruBTzPH
-3cioBnrJWKXc3OjXdLGFJOfj7pP0j/dr2LH72eSvv3PQQFl90CZPFhrCUcRHSSxo
-E6yjGOdnz7f6PveLIB574kQORwt8ePn0yidrTC1ictikED3nHYhMUOUCAwEAAaNT
-MFEwHQYDVR0OBBYEFPVV6xBUFPiGKDyo5V3+Hbh4N9YSMB8GA1UdIwQYMBaAFPVV
-6xBUFPiGKDyo5V3+Hbh4N9YSMA8GA1UdEwEB/wQFMAMBAf8wDQYJKoZIhvcNAQEL
-BQADggEBAGa9kS21N70ThM6/Hj9D7mbVxKLBjVWe2TPsGfbl3rEDfZ+OKRZ2j6AC
-6r7jb4TZO3dzF2p6dgbrlU71Y/4K0TdzIjRj3cQ3KSm41JvUQ0hZ/c04iGDg/xWf
-+pp58nfPAYwuerruPNWmlStWAXf0UTqRtg4hQDWBuUFDJTuWuuBvEXudz74eh/wK
-sMwfu1HFvjy5Z0iMDU8PUDepjVolOCue9ashlS4EB5IECdSR2TItnAIiIwimx839
-LdUdRudafMu5T5Xma182OC0/u/xRlEm+tvKGGmfFcN0piqVl8OrSPBgIlb+1IKJE
-m/XriWr/Cq4h/JfB7NTsezVslgkBaoU=
------END CERTIFICATE-----
-";
 
+            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

@@ -23,8 +23,7 @@ public static class Client_Publish_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder()
             .WithTcpServer("broker.hivemq.com")
             .Build();
@@ -42,7 +41,6 @@ public static class Client_Publish_Samples
 
         Console.WriteLine("MQTT application message is published.");
     }
-    }
 
     public static async Task Publish_Multiple_Application_Messages()
     {
@@ -54,8 +52,7 @@ public static class Client_Publish_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = new MqttClientOptionsBuilder()
             .WithTcpServer("broker.hivemq.com")
             .Build();
@@ -87,5 +84,4 @@ public static class Client_Publish_Samples
 
         Console.WriteLine("MQTT application message is published.");
     }
-    }
 }

Samples/Client/Client_Subscribe_Samples.cs

@@ -26,8 +26,7 @@ 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
@@ -52,7 +51,6 @@ public static class Client_Subscribe_Samples
         Console.WriteLine("Press enter to exit.");
         Console.ReadLine();
     }
-    }
 
     public static async Task Send_Responses()
     {
@@ -62,8 +60,7 @@ 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)
         {
             // Do some work with the message...
@@ -92,7 +89,6 @@ public static class Client_Subscribe_Samples
         // The response contains additional data sent by the server after subscribing.
         response.DumpToConsole();
     }
-    }
 
     public static async Task Subscribe_Multiple_Topics()
     {
@@ -102,8 +98,7 @@ 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();
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
@@ -123,7 +118,6 @@ public static class Client_Subscribe_Samples
         // The response contains additional data sent by the server after subscribing.
         response.DumpToConsole();
     }
-    }
 
     public static async Task Subscribe_Topic()
     {
@@ -133,8 +127,7 @@ 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();
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
@@ -148,7 +141,6 @@ public static class Client_Subscribe_Samples
         // 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

@@ -26,8 +26,7 @@ public static class Logger_Samples
             .WithTcpServer("broker.hivemq.com")
             .Build();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
         Console.WriteLine("MQTT client is connected.");
@@ -37,7 +36,6 @@ public static class Logger_Samples
 
         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}");
@@ -68,8 +66,7 @@ public static class Logger_Samples
             .WithTcpServer("broker.hivemq.com")
             .Build();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
         Console.WriteLine("MQTT client is connected.");
@@ -79,7 +76,6 @@ public static class Logger_Samples
 
         await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
     }
-    }
 
     sealed class MyLogger : IMqttNetLogger
     {

Samples/Diagnostics/PackageInspection_Samples.cs

@@ -20,8 +20,7 @@ public static class PackageInspection_Samples
 
         var mqttFactory = new MqttClientFactory();
 
-        using (var mqttClient = mqttFactory.CreateMqttClient())
+        using var mqttClient = mqttFactory.CreateMqttClient();
-        {
         var mqttClientOptions = mqttFactory.CreateClientOptionsBuilder()
             .WithTcpServer("broker.hivemq.com")
             .Build();
@@ -37,7 +36,6 @@ public static class PackageInspection_Samples
 
         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

@@ -26,8 +26,7 @@ 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();
@@ -43,7 +42,6 @@ public static class RpcClient_Samples
 
         Console.WriteLine("The RPC call was successful.");
     }
-    }
 
     /*
      * The device must respond to the request using the correct topic. The following C code shows how a

Samples/Server/Server_Diagnostics_Samples.cs

@@ -25,8 +25,7 @@ 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 =>
         {
@@ -37,7 +36,7 @@ public static class Server_Diagnostics_Samples
             Console.WriteLine($"QoS 1 reason code: {qos1AcknowledgePacket?.ReasonCode}");
 
             var qos2AcknowledgePacket = e.AcknowledgePacket as MqttPubCompPacket;
-                Console.WriteLine($"QoS 2 reason code: {qos1AcknowledgePacket?.ReasonCode}");
+            Console.WriteLine($"QoS 2 reason code: {qos2AcknowledgePacket?.ReasonCode}");
             return CompletedTask.Instance;
         };
 
@@ -48,5 +47,4 @@ public static class Server_Diagnostics_Samples
 
         await mqttServer.StopAsync();
     }
-    }
 }

Samples/Server/Server_Intercepting_Samples.cs

@@ -25,8 +25,7 @@ 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 =>
         {
             // Here we only change the topic of the received application message.
@@ -43,5 +42,4 @@ public static class Server_Intercepting_Samples
         Console.ReadLine();
         await mqttServer.StopAsync();
     }
-    }
 }

Samples/Server/Server_Retained_Messages_Samples.cs

@@ -29,8 +29,7 @@ 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 =>
         {
@@ -87,7 +86,6 @@ public static class Server_Retained_Messages_Samples
         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)
+            ArgumentNullException.ThrowIfNull(message);
-            {
-                throw new ArgumentNullException(nameof(message));
-            }
 
             return new MqttRetainedMessageModel
             {

Samples/Server/Server_Simple_Samples.cs

@@ -22,8 +22,7 @@ public static class Server_Simple_Samples
          * See _Run_Minimal_Server_ for more information.
          */
 
-        using (var mqttServer = await StartMqttServer())
+        using var mqttServer = await StartMqttServer();
-        {
         // Let the client connect.
         await Task.Delay(TimeSpan.FromSeconds(5));
 
@@ -34,7 +33,6 @@ public static class Server_Simple_Samples
             await affectedClient.DisconnectAsync();
         }
     }
-    }
 
     public static async Task Publish_Message_From_Broker()
     {
@@ -44,8 +42,7 @@ public static class Server_Simple_Samples
          * See _Run_Minimal_Server_ for more information.
          */
 
-        using (var mqttServer = await StartMqttServer())
+        using var mqttServer = await StartMqttServer();
-        {
         // Create a new message using the builder as usual.
         var message = new MqttApplicationMessageBuilder().WithTopic("HelloWorld").WithPayload("Test").Build();
 
@@ -56,7 +53,6 @@ public static class Server_Simple_Samples
                 SenderClientId = "SenderClientId"
             });
     }
-    }
 
     public static async Task Run_Minimal_Server()
     {
@@ -77,8 +73,7 @@ public static class Server_Simple_Samples
         //     .WithDefaultEndpointPort(1234)
         //     .Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
-        {
         await mqttServer.StartAsync();
 
         Console.WriteLine("Press Enter to exit.");
@@ -87,7 +82,6 @@ public static class Server_Simple_Samples
         // Stop and dispose the MQTT server if it is no longer needed!
         await mqttServer.StopAsync();
     }
-    }
 
     public static async Task Run_Server_With_Logging()
     {
@@ -103,8 +97,7 @@ public static class Server_Simple_Samples
 
         var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
-        {
         await mqttServer.StartAsync();
 
         Console.WriteLine("Press Enter to exit.");
@@ -113,7 +106,6 @@ public static class Server_Simple_Samples
         // Stop and dispose the MQTT server if it is no longer needed!
         await mqttServer.StopAsync();
     }
-    }
 
     public static async Task Validating_Connections()
     {
@@ -127,8 +119,7 @@ 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 =>
@@ -158,7 +149,6 @@ public static class Server_Simple_Samples
 
         await mqttServer.StopAsync();
     }
-    }
 
     static async Task<MqttServer> StartMqttServer()
     {

Samples/Server/Server_TLS_Samples.cs

@@ -31,8 +31,7 @@ public static class Server_TLS_Samples
 
         var mqttServerOptions = new MqttServerOptionsBuilder().WithEncryptionCertificate(certificate).WithEncryptedEndpoint().Build();
 
-        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
-        {
         await mqttServer.StartAsync();
 
         Console.WriteLine("Press Enter to exit.");
@@ -41,7 +40,6 @@ public static class Server_TLS_Samples
         // Stop and dispose the MQTT server if it is no longer needed!
         await mqttServer.StopAsync();
     }
-    }
 
     static X509Certificate2 CreateSelfSignedCertificate(string oid)
     {
@@ -50,8 +48,7 @@ public static class Server_TLS_Samples
         sanBuilder.AddIpAddress(IPAddress.IPv6Loopback);
         sanBuilder.AddDnsName("localhost");
 
-        using (var rsa = RSA.Create())
+        using var rsa = RSA.Create();
-        {
         var certRequest = new CertificateRequest("CN=localhost", rsa, HashAlgorithmName.SHA512, RSASignaturePadding.Pkcs1);
 
         certRequest.CertificateExtensions.Add(
@@ -61,8 +58,7 @@ public static class Server_TLS_Samples
 
         certRequest.CertificateExtensions.Add(sanBuilder.Build());
 
-            using (var certificate = certRequest.CreateSelfSigned(DateTimeOffset.Now.AddMinutes(-10), DateTimeOffset.Now.AddMinutes(10)))
+        using var certificate = certRequest.CreateSelfSigned(DateTimeOffset.Now.AddMinutes(-10), DateTimeOffset.Now.AddMinutes(10));
-            {
         var pfxCertificate = new X509Certificate2(
             certificate.Export(X509ContentType.Pfx),
             (string)null!,
@@ -70,6 +66,4 @@ public static class Server_TLS_Samples
 
         return pfxCertificate;
     }
-        }
-    }
 }

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

@@ -4,11 +4,11 @@
 
 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;
-    {
-        private readonly ILogger<IndexModel> _logger;
 
     public IndexModel(ILogger<IndexModel> logger)
     {
@@ -17,7 +17,6 @@ namespace MQTTnet.AspTestApp.Pages
 
     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))
+                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)
     {
         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)
     {
-            if (endpoints == null)
+        ArgumentNullException.ThrowIfNull(endpoints);
-            {
-                throw new ArgumentNullException(nameof(endpoints));
-            }
 
         endpoints.MapConnectionHandler<MqttConnectionHandler>(pattern, options =>
         {
             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">
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-            <Pack>True</Pack>
+        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
-            <PackagePath>\</PackagePath>
-        </None>
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.AspnetCore/MqttClientConnectionContextFactory.cs

@@ -7,10 +7,10 @@ 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)
     {
         if (options == null) throw new ArgumentNullException(nameof(options));
@@ -30,5 +30,4 @@ namespace MQTTnet.AspNetCore
             }
         }
     }
-    }
 }

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

@@ -33,15 +33,13 @@ 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)
         {
             await clientHandler(adapter).ConfigureAwait(false);
         }
     }
-    }
 
     public Task StartAsync(MqttServerOptions options, IMqttNetLogger logger)
     {

Source/MQTTnet.AspnetCore/MqttSubProtocolSelector.cs

@@ -13,10 +13,7 @@ public static class MqttSubProtocolSelector
 {
     public static string SelectSubProtocol(HttpRequest request)
     {
-        if (request == null)
+        ArgumentNullException.ThrowIfNull(request);
-        {
-            throw new ArgumentNullException(nameof(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)
+        ArgumentNullException.ThrowIfNull(requestedSubProtocolValues);
-        {
-            throw new ArgumentNullException(nameof(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)
+        ArgumentNullException.ThrowIfNull(webSocket);
-        {
-            throw new ArgumentNullException(nameof(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
@@ -42,14 +41,12 @@ 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))
+                using var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger);
-                {
                 await clientHandler(channelAdapter).ConfigureAwait(false);
             }
         }
-        }
         finally
         {
             clientCertificate?.Dispose();

Source/MQTTnet.AspnetCore/ReaderExtensions.cs

@@ -22,10 +22,7 @@ public static class ReaderExtensions
         out SequencePosition observed,
         out int bytesRead)
     {
-        if (formatter == null)
+        ArgumentNullException.ThrowIfNull(formatter);
-        {
-            throw new ArgumentNullException(nameof(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)
+        ArgumentNullException.ThrowIfNull(services);
-        {
+        ArgumentNullException.ThrowIfNull(options);
-            throw new ArgumentNullException(nameof(services));
-        }
-
-        if (options == null)
-        {
-            throw new ArgumentNullException(nameof(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)
+        ArgumentNullException.ThrowIfNull(services);
-        {
-            throw new ArgumentNullException(nameof(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)
+        ArgumentNullException.ThrowIfNull(services);
-        {
-            throw new ArgumentNullException(nameof(services));
-        }
 
         services.AddSingleton(
             s =>
@@ -89,20 +76,14 @@ public static class ServiceCollectionExtensions
 
     public static void AddMqttLogger(this IServiceCollection services, IMqttNetLogger logger)
     {
-        if (services == null)
+        ArgumentNullException.ThrowIfNull(services);
-        {
-            throw new ArgumentNullException(nameof(services));
-        }
 
         services.AddSingleton(logger);
     }
 
     public static IServiceCollection AddMqttServer(this IServiceCollection serviceCollection, Action<MqttServerOptionsBuilder> configure = null)
     {
-        if (serviceCollection is null)
+        ArgumentNullException.ThrowIfNull(serviceCollection);
-        {
-            throw new ArgumentNullException(nameof(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)
+    public bool IsCompleted => ReferenceEquals(_callback, CallbackCompleted);
-    {
-        _ioScheduler = ioScheduler;
-    }
-
-    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 ||
+        catch (SocketException ex) when (ex.SocketErrorCode is SocketError.OperationAborted or SocketError.ConnectionAborted or SocketError.Interrupted or SocketError.InvalidArgument)
-                                         ex.SocketErrorCode == SocketError.Interrupted || ex.SocketErrorCode == 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

@@ -9,12 +9,12 @@ 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()
     {
@@ -52,8 +52,7 @@ namespace MQTTnet.Benchmarks
     {
         var asyncLock = new AsyncLock();
 
-            using (var cancellationToken = new CancellationTokenSource())
+        using var cancellationToken = new CancellationTokenSource();
-            {
         for (var i = 0; i < 100000; i++)
         {
             using (await asyncLock.EnterAsync(cancellationToken.Token).ConfigureAwait(false))
@@ -61,6 +60,4 @@ namespace MQTTnet.Benchmarks
             }
         }
     }
-        }
-    }
 }

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

@@ -12,11 +12,11 @@ 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;
@@ -86,5 +86,4 @@ namespace MQTTnet.Benchmarks
 
         return buffer.ToArray();
     }
-    }
 }

Source/MQTTnet.Benchmarks/LoggerBenchmark.cs

@@ -2,17 +2,18 @@
 // 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;
 
@@ -42,7 +43,7 @@ namespace MQTTnet.Benchmarks
     {
         if (_useHandler)
         {
-                eventArgs.LogMessage.ToString();
+            Debug.WriteLine(eventArgs.LogMessage.ToString());
         }
     }
 
@@ -87,5 +88,4 @@ namespace MQTTnet.Benchmarks
             _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

@@ -3,16 +3,17 @@ using BenchmarkDotNet.Jobs;
 using System;
 
 
-namespace MQTTnet.Benchmarks
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class MemoryCopyBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
+    const int MaxLength = 1024 * 8;
-    [RPlotExporter, RankColumn]
+
-    [MemoryDiagnoser]
+    byte[] _source;
-    public class MemoryCopyBenchmark
+    byte[] _target;
-    {
-        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; }
@@ -20,21 +21,20 @@ namespace MQTTnet.Benchmarks
     [GlobalSetup]
     public void Setup()
     {
-            source = new byte[max_length];
+        _source = new byte[MaxLength];
-            target = new byte[max_length];
+        _target = new byte[MaxLength];
     }
 
     [Benchmark(Baseline = true)]
     public void Array_Copy()
     {
-            Array.Copy(source, 0, target, 0, Length);
+        Array.Copy(_source, 0, _target, 0, Length);
     }
 
     [Benchmark]
     public void Memory_Copy()
     {
-            MQTTnet.Internal.MqttMemoryHelper.Copy(source, 0, target, 0, Length);
+        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;
+        TopicGenerator.Generate(_numPublishers, _numTopicsPerPublisher, out _topicsByPublisher, out _, out _);
-        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);
-        }
 
         // 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 totalNumTopics = _numPublishers * _numTopicsPerPublisher;
-        var topicIndexStep = totalNumTopics / (NumSubscribedTopicsPerSubscriber * NumSubscribers);
+        var topicIndexStep = totalNumTopics / (_numSubscribedTopicsPerSubscriber * _numSubscribers);
-        if (topicIndexStep * NumSubscribedTopicsPerSubscriber * NumSubscribers != totalNumTopics)
+        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: {totalNumTopics}, topic step: {topicIndexStep}");
-                    "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));
         }
 
         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

@@ -9,12 +9,12 @@ 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;
@@ -30,7 +30,7 @@ namespace MQTTnet.Benchmarks
                     .AddMqttConnectionHandler();
             })
             .Configure(app => {
-                       app.UseMqttServer(s => {
+                app.UseMqttServer(_ => {
 
                 });
             })
@@ -69,5 +69,4 @@ namespace MQTTnet.Benchmarks
             _mqttClient.PublishAsync(_message).GetAwaiter().GetResult();
         }
     }
-    }
 }

Source/MQTTnet.Benchmarks/MqttBufferReaderBenchmark.cs

@@ -8,12 +8,12 @@ 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;
 
@@ -39,5 +39,4 @@ namespace MQTTnet.Benchmarks
     {
         Encoding.UTF8.GetString(_buffer, 0, _bufferLength);
     }
-    }
 }

Source/MQTTnet.Benchmarks/MqttPacketReaderWriterBenchmark.cs

@@ -8,12 +8,12 @@ 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;
@@ -92,5 +92,4 @@ namespace MQTTnet.Benchmarks
             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

@@ -5,14 +5,12 @@
 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;
 
@@ -138,5 +136,4 @@ namespace MQTTnet.Benchmarks
 
         Console.WriteLine();
     }
-    }
 }

Source/MQTTnet.Benchmarks/ReaderExtensionsBenchmark.cs

@@ -1,31 +1,27 @@
 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
+namespace MQTTnet.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter, RankColumn]
+[MemoryDiagnoser]
+public class ReaderExtensionsBenchmark
 {
-    [SimpleJob(RuntimeMoniker.Net60)]
+    MqttPacketFormatterAdapter _mqttPacketFormatter;
-    [RPlotExporter, RankColumn]
+    MemoryStream _stream;
-    [MemoryDiagnoser]
-    public class ReaderExtensionsBenchmark
-    {
-        MqttPacketFormatterAdapter mqttPacketFormatter;
-        MemoryStream stream;
 
     [GlobalSetup]
     public void GlobalSetup()
     {
-            mqttPacketFormatter = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
+        _mqttPacketFormatter = new MqttPacketFormatterAdapter(MqttProtocolVersion.V311, new MqttBufferWriter(4096, 65535));
         var mqttMessage = new MqttApplicationMessageBuilder()
             .WithTopic("topic")
             .WithPayload(new byte[10 * 1024])
@@ -33,66 +29,18 @@ namespace MQTTnet.Benchmarks
 
         var packet = MqttPublishPacketFactory.Create(mqttMessage);
 
-            var buffer = mqttPacketFormatter.Encode(packet);
+        var buffer = _mqttPacketFormatter.Encode(packet);
-            stream = new MemoryStream();
+        _stream = new MemoryStream();
-            stream.Write(buffer.Packet);
+        _stream.Write(buffer.Packet);
-            stream.Write(buffer.Payload.ToArray());
+        _stream.Write(buffer.Payload.ToArray());
-            mqttPacketFormatter.Cleanup();
+        _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;
+        _stream.Position = 0;
-            var input = PipeReader.Create(stream);
+        var input = PipeReader.Create(_stream);
 
         while (true)
         {
@@ -116,7 +64,7 @@ namespace MQTTnet.Benchmarks
             {
                 if (!buffer.IsEmpty)
                 {
-                        if (ReaderExtensions.TryDecode(mqttPacketFormatter, buffer, out var packet, out consumed, out observed, out var received))
+                    if (_mqttPacketFormatter.TryDecode(buffer, out _, out consumed, out observed, out _))
                     {
                         break;
                     }
@@ -135,106 +83,4 @@ namespace MQTTnet.Benchmarks
             }
         }
     }
-
-        public static class ReaderExtensions_Before
-        {
-            public static bool TryDecode(MqttPacketFormatterAdapter formatter,
-                in ReadOnlySequence<byte> input,
-                out MqttPacket packet,
-                out SequencePosition consumed,
-                out SequencePosition observed,
-                out int bytesRead)
-            {
-                if (formatter == null) throw new ArgumentNullException(nameof(formatter));
-
-                packet = null;
-                consumed = input.Start;
-                observed = input.End;
-                bytesRead = 0;
-                var copy = input;
-
-                if (copy.Length < 2)
-                {
-                    return false;
-                }
-
-                var fixedHeader = copy.First.Span[0];
-                if (!TryReadBodyLength(ref copy, out int headerLength, out var bodyLength))
-                {
-                    return false;
-                }
-
-                if (copy.Length < bodyLength)
-                {
-                    return false;
-                }
-
-                var bodySlice = copy.Slice(0, bodyLength);
-                var buffer = GetMemory(bodySlice).ToArray();
-
-                var receivedMqttPacket = new ReceivedMqttPacket(fixedHeader, new ArraySegment<byte>(buffer, 0, buffer.Length), buffer.Length + 2);
-
-                if (formatter.ProtocolVersion == MqttProtocolVersion.Unknown)
-                {
-                    formatter.DetectProtocolVersion(receivedMqttPacket);
-                }
-
-                packet = formatter.Decode(receivedMqttPacket);
-                consumed = bodySlice.End;
-                observed = bodySlice.End;
-                bytesRead = headerLength + bodyLength;
-                return true;
-            }
-
-            static ReadOnlyMemory<byte> GetMemory(in ReadOnlySequence<byte> input)
-            {
-                if (input.IsSingleSegment)
-                {
-                    return input.First;
-                }
-
-                // Should be rare
-                return input.ToArray();
-            }
-
-            static bool TryReadBodyLength(ref ReadOnlySequence<byte> input, out int headerLength, out int bodyLength)
-            {
-                // Alorithm taken from https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/errata01/os/mqtt-v3.1.1-errata01-os-complete.html.
-                var multiplier = 1;
-                var value = 0;
-                byte encodedByte;
-                var index = 1;
-                headerLength = 0;
-                bodyLength = 0;
-
-                var temp = GetMemory(input.Slice(0, Math.Min(5, input.Length))).Span;
-
-                do
-                {
-                    if (index == temp.Length)
-                    {
-                        return false;
-                    }
-
-                    encodedByte = temp[index];
-                    index++;
-
-                    value += (byte)(encodedByte & 127) * multiplier;
-                    if (multiplier > 128 * 128 * 128)
-                    {
-                        throw new MqttProtocolViolationException($"Remaining length is invalid (Data={string.Join(",", temp.Slice(1, index).ToArray())}).");
-                    }
-
-                    multiplier *= 128;
-                } while ((encodedByte & 128) != 0);
-
-                input = input.Slice(index);
-
-                headerLength = index;
-                bodyLength = value;
-                return true;
-            }
-        }
-
-    }
 }

Source/MQTTnet.Benchmarks/RoundtripProcessingBenchmark.cs

@@ -3,13 +3,13 @@ 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()
     {
@@ -24,7 +24,6 @@ namespace MQTTnet.Benchmarks
     [Benchmark]
     public void Handle_100_000_Messages_In_Receiving_Client()
     {
-            new Load_Tests().Handle_100_000_Messages_In_Receiving_Client().GetAwaiter().GetResult();
+        //new Load_Tests().Handle_100_000_Messages_In_Receiving_Client().GetAwaiter().GetResult();
-        }
     }
 }

Source/MQTTnet.Benchmarks/SendPacketAsyncBenchmark.cs

@@ -7,52 +7,51 @@ 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)]
+    MemoryStream _stream;
-    [RPlotExporter, RankColumn]
+    MqttPacketBuffer _buffer;
-    [MemoryDiagnoser]
-    public class SendPacketAsyncBenchmark : BaseBenchmark
-    {
-        MemoryStream stream;
-        MqttPacketBuffer buffer;
 
     [GlobalSetup]
     public void GlobalSetup()
     {
-            stream = new MemoryStream(1024);
+        _stream = new MemoryStream(1024);
         var packet = new ArraySegment<byte>(new byte[10]);
-            buffer = new MqttPacketBuffer(packet);
+        _buffer = new MqttPacketBuffer(packet);
     }
 
     [Benchmark(Baseline = true)]
     public async ValueTask Before()
     {
-            stream.Position = 0;
+        _stream.Position = 0;
-            var output = PipeWriter.Create(stream);
+        var output = PipeWriter.Create(_stream);
 
-            WritePacketBuffer(output, buffer);
+        WritePacketBuffer(output, _buffer);
         await output.FlushAsync();
     }
 
     [Benchmark]
     public async ValueTask After()
     {
-            stream.Position = 0;
+        _stream.Position = 0;
-            var output = PipeWriter.Create(stream);
+        var output = PipeWriter.Create(_stream);
 
-            if (buffer.Payload.Length == 0)
+        if (_buffer.Payload.Length == 0)
         {
-                await output.WriteAsync(buffer.Packet).ConfigureAwait(false);
+            await output.WriteAsync(_buffer.Packet).ConfigureAwait(false);
         }
         else
         {
-                WritePacketBuffer(output, buffer);
+            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
@@ -61,9 +60,8 @@ namespace MQTTnet.Benchmarks
         var span = output.GetSpan(buffer.Length);
 
         buffer.Packet.AsSpan().CopyTo(span);
-            buffer.Payload.CopyTo(span.Slice(buffer.Packet.Count));
+        buffer.Payload.CopyTo(span[buffer.Packet.Count..]);
 
         output.Advance(buffer.Length);
     }
-    }
 }

Source/MQTTnet.Benchmarks/SerializerBenchmark.cs

@@ -15,14 +15,15 @@ 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;
@@ -61,7 +62,7 @@ namespace MQTTnet.Benchmarks
         {
             channel.Reset();
 
-                var header = reader.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
+            reader.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
         }
     }
 
@@ -76,11 +77,11 @@ namespace MQTTnet.Benchmarks
             _position = _buffer.Offset;
         }
 
-            public string Endpoint { get; } = string.Empty;
+        public EndPoint RemoteEndPoint { get; set; }
 
         public bool IsSecureConnection { get; } = false;
 
-            public X509Certificate2 ClientCertificate { get; }
+        public X509Certificate2 ClientCertificate { get; set; }
 
         public void Reset()
         {
@@ -99,7 +100,7 @@ namespace MQTTnet.Benchmarks
 
         public Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
         {
-                Array.Copy(_buffer.Array, _position, buffer, offset, count);
+            Array.Copy(_buffer!.Array!, _position, buffer, offset, count);
             _position += count;
 
             return Task.FromResult(count);
@@ -114,5 +115,4 @@ namespace MQTTnet.Benchmarks
         {
         }
     }
-    }
 }

Source/MQTTnet.Benchmarks/ServerProcessingBenchmark.cs

@@ -7,13 +7,13 @@ 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()
     {
@@ -28,13 +28,12 @@ namespace MQTTnet.Benchmarks
     [Benchmark]
     public void Handle_100_000_Messages_In_Server_MqttClient()
     {
-            new Load_Tests().Handle_100_000_Messages_In_Server().GetAwaiter().GetResult();
+        //new Load_Tests().Handle_100_000_Messages_In_Server().GetAwaiter().GetResult();
     }
 
-        //[Benchmark]
+    [Benchmark]
     public void Handle_100_000_Messages_In_Server_LowLevelMqttClient()
     {
-            new Load_Tests().Handle_100_000_Messages_In_Low_Level_Client().GetAwaiter().GetResult();
+        //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

@@ -11,12 +11,12 @@ 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;
 
@@ -76,5 +76,4 @@ namespace MQTTnet.Benchmarks
             await output.WriteAsync(new byte[size], CancellationToken.None).ConfigureAwait(false);
         }
     }
-    }
 }

Source/MQTTnet.Benchmarks/TopicFilterComparerBenchmark.cs

@@ -2,19 +2,16 @@
 // 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
-    {
-        static readonly char[] TopicLevelSeparator = { '/' };
 
+[SimpleJob(RuntimeMoniker.Net60)]
+[RPlotExporter]
+[MemoryDiagnoser]
+public class TopicFilterComparerBenchmark : BaseBenchmark
+{
     readonly string _longTopic =
         "AAAAAAAAAAAAAssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
 
@@ -33,245 +30,4 @@ namespace MQTTnet.Benchmarks
             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;
-            }
-        }
-    }
 }

Source/MQTTnet.Benchmarks/TopicGenerator.cs

@@ -1,10 +1,10 @@
 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,
@@ -80,5 +80,4 @@ namespace MQTTnet.Benchmarks
 
         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

@@ -4,16 +4,13 @@
 
 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)
     {
-            if (context == null)
+        ArgumentNullException.ThrowIfNull(context);
-            {
-                throw new ArgumentNullException(nameof(context));
-            }
 
         if (context.MethodName.Contains("/") || context.MethodName.Contains("+") || context.MethodName.Contains("#"))
         {
@@ -29,5 +26,4 @@ namespace MQTTnet.Extensions.Rpc
             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
-    {
-        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);
+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);
 }

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);
-    }
 }

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">
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-            <Pack>True</Pack>
+        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
-            <PackagePath>\</PackagePath>
-        </None>
     </ItemGroup>
 
     <ItemGroup>

Source/MQTTnet.Extensions.Rpc/MqttFactoryExtensions.cs

@@ -4,10 +4,10 @@
 
 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)
     {
         return clientFactory.CreateMqttRpcClient(
@@ -20,17 +20,9 @@ namespace MQTTnet.Extensions.Rpc
 
     public static IMqttRpcClient CreateMqttRpcClient(this MqttClientFactory _, IMqttClient mqttClient, MqttRpcClientOptions rpcClientOptions)
     {
-            if (mqttClient == null)
+        ArgumentNullException.ThrowIfNull(mqttClient);
-            {
+        ArgumentNullException.ThrowIfNull(rpcClientOptions);
-                throw new ArgumentNullException(nameof(mqttClient));
-            }
-
-            if (rpcClientOptions == null)
-            {
-                throw new ArgumentNullException(nameof(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;
@@ -14,14 +13,14 @@ using MQTTnet.Formatter;
 using MQTTnet.Internal;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Extensions.Rpc
+namespace MQTTnet.Extensions.Rpc;
+
+public sealed class MqttRpcClient : IMqttRpcClient
 {
-    public sealed class MqttRpcClient : IMqttRpcClient
-    {
     readonly IMqttClient _mqttClient;
     readonly MqttRpcClientOptions _options;
 
-        readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>>();
+    readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new();
 
     public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
     {
@@ -43,10 +42,14 @@ namespace MQTTnet.Extensions.Rpc
         _waitingCalls.Clear();
     }
 
-        public async Task<byte[]> ExecuteAsync(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null)
+    public async Task<byte[]> ExecuteAsync(
-        {
+        TimeSpan timeout,
-            using (var timeoutToken = new CancellationTokenSource(timeout))
+        string methodName,
+        byte[] payload,
+        MqttQualityOfServiceLevel qualityOfServiceLevel,
+        IDictionary<string, object>? parameters = null)
     {
+        using var timeoutToken = new CancellationTokenSource(timeout);
         try
         {
             return await ExecuteAsync(methodName, payload, qualityOfServiceLevel, parameters, timeoutToken.Token).ConfigureAwait(false);
@@ -61,14 +64,15 @@ namespace MQTTnet.Extensions.Rpc
             throw;
         }
     }
-        }
 
-        public async Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default)
+    public async Task<byte[]> ExecuteAsync(
+        string methodName,
+        byte[] payload,
+        MqttQualityOfServiceLevel qualityOfServiceLevel,
+        IDictionary<string, object>? parameters = null,
+        CancellationToken cancellationToken = default)
     {
-            if (methodName == null)
+        ArgumentNullException.ThrowIfNull(methodName);
-            {
-                throw new ArgumentNullException(nameof(methodName));
-            }
 
         var context = new TopicGenerationContext(_mqttClient, _options, methodName, parameters, qualityOfServiceLevel);
         var topicNames = _options.TopicGenerationStrategy.CreateRpcTopics(context);
@@ -88,7 +92,7 @@ namespace MQTTnet.Extensions.Rpc
 
         var requestMessageBuilder = new MqttApplicationMessageBuilder().WithTopic(requestTopic).WithPayload(payload).WithQualityOfServiceLevel(qualityOfServiceLevel);
 
-            if (_mqttClient.Options.ProtocolVersion == MqttProtocolVersion.V500)
+        if (_mqttClient.Options!.ProtocolVersion == MqttProtocolVersion.V500)
         {
             requestMessageBuilder.WithResponseTopic(responseTopic);
         }
@@ -109,8 +113,7 @@ namespace MQTTnet.Extensions.Rpc
             await _mqttClient.SubscribeAsync(subscribeOptions, cancellationToken).ConfigureAwait(false);
             await _mqttClient.PublishAsync(requestMessage, cancellationToken).ConfigureAwait(false);
 
-                using (cancellationToken.Register(
+            using (cancellationToken.Register(() =>
-                           () =>
                    {
                        awaitable.TrySetCanceled();
                    }))
@@ -140,5 +143,4 @@ namespace MQTTnet.Extensions.Rpc
 
         return CompletedTask.Instance;
     }
-    }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClientExtensions.cs

@@ -8,11 +8,11 @@ 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));
 
@@ -20,5 +20,4 @@ namespace MQTTnet.Extensions.Rpc
 
         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();
-    }
 }

Source/MQTTnet.Extensions.Rpc/MqttRpcClientOptionsBuilder.cs

@@ -4,10 +4,10 @@
 
 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()
@@ -24,5 +24,4 @@ namespace MQTTnet.Extensions.Rpc
 
         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
+namespace MQTTnet.Extensions.Rpc;
-{
-    public sealed class MqttRpcTopicPair
-    {
-        public string RequestTopic { get; set; }
 
-        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

@@ -6,12 +6,16 @@ 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,
-        public TopicGenerationContext(IMqttClient mqttClient, MqttRpcClientOptions options, string methodName,
+        MqttRpcClientOptions options,
-            IDictionary<string, object> parameters, MqttQualityOfServiceLevel qualityOfServiceLevel)
+        string methodName,
+        IDictionary<string, object>? parameters,
+        MqttQualityOfServiceLevel qualityOfServiceLevel)
     {
         MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
         Parameters = parameters;
@@ -22,12 +26,12 @@ namespace MQTTnet.Extensions.Rpc
 
     public string MethodName { get; }
 
-        public IDictionary<string, object> Parameters { 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
@@ -38,5 +42,4 @@ namespace MQTTnet.Extensions.Rpc
     ///     - 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" />
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-        <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+        <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)
+        ArgumentNullException.ThrowIfNull(topicTemplate);
-        {
-            throw new ArgumentNullException(nameof(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

@@ -5,10 +5,10 @@
 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;
 
     /// <summary>
@@ -28,5 +28,4 @@ namespace MQTTnet.Server
     ///     <remarks>MQTT 5.0.0+ feature.</remarks>
     /// </summary>
     public List<MqttUserProperty> UserProperties { get; set; }
-    }
 }

Source/MQTTnet.Server/Disconnecting/MqttServerClientDisconnectOptionsBuilder.cs

@@ -5,10 +5,10 @@
 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()
@@ -50,5 +50,4 @@ namespace MQTTnet.Server
         _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

@@ -2,12 +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.
 
-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)
     {
         SenderClientId = senderClientId ?? throw new ArgumentNullException( nameof(senderClientId));
@@ -23,5 +21,4 @@ namespace MQTTnet.Server
     public bool IsDropped { get; }
 
     public MqttApplicationMessage ApplicationMessage { get; }
-    }
 }

Source/MQTTnet.Server/Events/ApplicationMessageNotConsumedEventArgs.cs

@@ -2,12 +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.
 
-using System;
+namespace MQTTnet.Server;
 
-namespace MQTTnet.Server
+public sealed class ApplicationMessageNotConsumedEventArgs : EventArgs
 {
-    public sealed class ApplicationMessageNotConsumedEventArgs : EventArgs
-    {
     public ApplicationMessageNotConsumedEventArgs(MqttApplicationMessage applicationMessage, string senderId)
     {
         ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
@@ -23,5 +21,4 @@ namespace MQTTnet.Server
     ///     Gets the ID of the client which has sent the affected application message.
     /// </summary>
     public string SenderId { get; }
-    }
 }

Source/MQTTnet.Server/Events/ClientAcknowledgedPublishPacketEventArgs.cs

@@ -2,17 +2,17 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 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));
+        UserName = userName;
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
         PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
         AcknowledgePacket = acknowledgePacket ?? throw new ArgumentNullException(nameof(acknowledgePacket));
@@ -28,6 +28,11 @@ namespace MQTTnet.Server
     /// </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>
@@ -42,5 +47,4 @@ namespace MQTTnet.Server
     ///     Gets the session items which contain custom user data per session.
     /// </summary>
     public IDictionary SessionItems { get; }
-    }
 }

Source/MQTTnet.Server/Events/ClientConnectedEventArgs.cs

@@ -2,40 +2,43 @@
 // 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, string endpoint, IDictionary sessionItems)
+    public ClientConnectedEventArgs(MqttConnectPacket connectPacket, MqttProtocolVersion protocolVersion, EndPoint remoteEndPoint, IDictionary sessionItems)
     {
         _connectPacket = connectPacket ?? throw new ArgumentNullException(nameof(connectPacket));
         ProtocolVersion = protocolVersion;
-            Endpoint = endpoint;
+        RemoteEndPoint = remoteEndPoint;
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
 
-        public byte[] AuthenticationData => _connectPacket.AuthenticationData;
+    public byte[]? AuthenticationData => _connectPacket.AuthenticationData;
 
-        public string AuthenticationMethod => _connectPacket.AuthenticationMethod;
+    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;
+    public string ClientId => _connectPacket.ClientId!;
 
     /// <summary>
     ///     Gets the endpoint of the connected client.
     /// </summary>
-        public string Endpoint { get; }
+    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.
@@ -50,12 +53,16 @@ namespace MQTTnet.Server
     /// <summary>
     ///     Gets the user name of the connected client.
     /// </summary>
-        public string UserName => _connectPacket.Username;
+    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;
+    public List<MqttUserProperty>? UserProperties => _connectPacket?.UserProperties;
-    }
 }

Source/MQTTnet.Server/Events/ClientDisconnectedEventArgs.cs

@@ -2,30 +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;
-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(
-            string clientId,
+        MqttConnectPacket connectPacket,
         MqttDisconnectPacket disconnectPacket,
         MqttClientDisconnectType disconnectType,
-            string endpoint,
+        EndPoint remoteEndPoint,
         IDictionary sessionItems)
     {
-            ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
         DisconnectType = disconnectType;
-            Endpoint = endpoint;
+        RemoteEndPoint = remoteEndPoint;
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
 
+        _connectPacket = connectPacket;
         // The DISCONNECT packet can be null in case of a non clean disconnect or session takeover.
         _disconnectPacket = disconnectPacket;
     }
@@ -34,11 +35,24 @@ namespace MQTTnet.Server
     ///     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 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 string Endpoint { get; }
+    public EndPoint RemoteEndPoint { get; }
+
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string? Endpoint => RemoteEndPoint?.ToString();
 
     /// <summary>
     ///     Gets the reason code sent by the client.
@@ -52,7 +66,7 @@ namespace MQTTnet.Server
     ///     Only available for clean disconnects.
     ///     <remarks>MQTT 5.0.0+ feature.</remarks>
     /// </summary>
-        public string ReasonString => _disconnectPacket?.ReasonString;
+    public string? ReasonString => _disconnectPacket?.ReasonString;
 
     /// <summary>
     ///     Gets the session expiry interval sent by the client.
@@ -71,6 +85,5 @@ namespace MQTTnet.Server
     ///     Only available for clean disconnects.
     ///     <remarks>MQTT 5.0.0+ feature.</remarks>
     /// </summary>
-        public List<MqttUserProperty> UserProperties => _disconnectPacket?.UserProperties;
+    public List<MqttUserProperty>? UserProperties => _disconnectPacket?.UserProperties;
-    }
 }

Source/MQTTnet.Server/Events/ClientSubscribedTopicEventArgs.cs

@@ -2,17 +2,17 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 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));
+        UserName = userName;
         TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
@@ -23,6 +23,11 @@ namespace MQTTnet.Server
     /// </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>
@@ -33,5 +38,4 @@ namespace MQTTnet.Server
     ///     The topic filter can contain topics and wildcards.
     /// </summary>
     public MqttTopicFilter TopicFilter { get; }
-    }
 }

Source/MQTTnet.Server/Events/ClientUnsubscribedTopicEventArgs.cs

@@ -2,16 +2,16 @@
 // 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));
+        UserName = userName;
         TopicFilter = topicFilter ?? throw new ArgumentNullException(nameof(topicFilter));
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
@@ -22,6 +22,11 @@ namespace MQTTnet.Server
     /// </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>
@@ -32,5 +37,4 @@ namespace MQTTnet.Server
     ///     The topic filter can contain topics and wildcards.
     /// </summary>
     public string TopicFilter { get; }
-    }
 }

Source/MQTTnet.Server/Events/InterceptingClientApplicationMessageEnqueueEventArgs.cs

@@ -2,12 +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.
 
-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)
     {
         SenderClientId = senderClientId ?? throw new ArgumentNullException(nameof(senderClientId));
@@ -31,5 +29,4 @@ namespace MQTTnet.Server
     public string ReceiverClientId { get; }
 
     public string SenderClientId { get; }
-    }
 }

Source/MQTTnet.Server/Events/InterceptingPacketEventArgs.cs

@@ -2,20 +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;
-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;
+        UserName = userName;
+        RemoteEndPoint = remoteEndPoint;
         Packet = packet ?? throw new ArgumentNullException(nameof(packet));
         SessionItems = sessionItems;
     }
@@ -31,10 +31,18 @@ namespace MQTTnet.Server
     /// </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 string Endpoint { get; }
+    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.
@@ -50,5 +58,4 @@ namespace MQTTnet.Server
     ///     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

@@ -2,19 +2,18 @@
 // 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));
+        UserName = userName;
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
 
@@ -31,6 +30,11 @@ namespace MQTTnet.Server
     /// </summary>
     public string ClientId { get; }
 
+    /// <summary>
+    /// Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
     public bool CloseConnection { get; set; }
 
     /// <summary>
@@ -47,5 +51,4 @@ namespace MQTTnet.Server
     ///     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

@@ -2,25 +2,24 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using 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)
     {
         CancellationToken = cancellationToken;
         ClientId = clientId;
+        UserName = userName;
         Session = session;
         TopicFilter = topicFilter;
         UserProperties = userProperties;
@@ -37,6 +36,11 @@ namespace MQTTnet.Server
     /// </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>
@@ -80,5 +84,4 @@ namespace MQTTnet.Server
     ///     <remarks>MQTT 5.0.0+ feature.</remarks>
     /// </summary>
     public List<MqttUserProperty> UserProperties { get; set; }
-    }
 }

Source/MQTTnet.Server/Events/InterceptingUnsubscriptionEventArgs.cs

@@ -2,20 +2,18 @@
 // 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;
+        UserName = userName;
         SessionItems = sessionItems;
         Topic = topic;
         UserProperties = userProperties;
@@ -32,6 +30,11 @@ namespace MQTTnet.Server
     /// </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>
@@ -68,5 +71,4 @@ namespace MQTTnet.Server
     ///     <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;
+namespace MQTTnet.Server;
-using System.Collections.Generic;
 
-namespace MQTTnet.Server
+public sealed class LoadingRetainedMessagesEventArgs : EventArgs
 {
-    public sealed class LoadingRetainedMessagesEventArgs : EventArgs
-    {
     public List<MqttApplicationMessage> LoadedRetainedMessages { get; set; } = new List<MqttApplicationMessage>();
-    }
 }

Source/MQTTnet.Server/Events/PreparingSessionEventArgs.cs

@@ -2,15 +2,13 @@
 // 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; }
 
     // TODO: Allow adding of packets to the queue etc.
@@ -47,5 +45,4 @@ namespace MQTTnet.Server
     // </summary>
     // TODO: Use single properties. No entire will message.
     //MqttApplicationMessage WillMessage { get; set; }
-    }
 }

Source/MQTTnet.Server/Events/QueueMessageOverwrittenEventArgs.cs

@@ -2,13 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-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)
     {
         ReceiverClientId = receiverClientId ?? throw new ArgumentNullException(nameof(receiverClientId));
@@ -18,5 +17,4 @@ namespace MQTTnet.Server
     public MqttPacket Packet { get; }
 
     public string ReceiverClientId { get; }
-    }
 }

Source/MQTTnet.Server/Events/RetainedMessageChangedEventArgs.cs

@@ -2,13 +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.
 
-using System;
+namespace MQTTnet.Server;
-using System.Collections.Generic;
 
-namespace MQTTnet.Server
+public sealed class RetainedMessageChangedEventArgs : EventArgs
 {
-    public sealed class RetainedMessageChangedEventArgs : EventArgs
-    {
     public RetainedMessageChangedEventArgs(string clientId, MqttApplicationMessage changedRetainedMessage, List<MqttApplicationMessage> storedRetainedMessages)
     {
         ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
@@ -21,5 +18,4 @@ namespace MQTTnet.Server
     public string ClientId { get; }
 
     public List<MqttApplicationMessage> StoredRetainedMessages { get; }
-    }
 }

Source/MQTTnet.Server/Events/SessionDeletedEventArgs.cs

@@ -2,16 +2,16 @@
 // 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));
+        UserName = userName;
         SessionItems = sessionItems ?? throw new ArgumentNullException(nameof(sessionItems));
     }
 
@@ -20,9 +20,13 @@ namespace MQTTnet.Server
     /// </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

@@ -2,28 +2,30 @@
 // 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;
 
-        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>
@@ -44,6 +46,8 @@ namespace MQTTnet.Server
     /// </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.
@@ -70,7 +74,8 @@ namespace MQTTnet.Server
     /// </summary>
     public string ClientId => _connectPacket.ClientId;
 
-        public string Endpoint => ChannelAdapter.Endpoint;
+    [Obsolete("Use RemoteEndPoint instead.")]
+    public string Endpoint => RemoteEndPoint?.ToString();
 
     public bool IsSecureConnection => ChannelAdapter.IsSecureConnection;
 
@@ -107,11 +112,13 @@ namespace MQTTnet.Server
 
     /// <summary>
     ///     Gets or sets the receive maximum.
-        ///     This gives the maximum length of the receive messages.
+    ///     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>
@@ -181,10 +188,57 @@ namespace MQTTnet.Server
     public List<MqttUserProperty> UserProperties => _connectPacket.UserProperties;
 
     /// <summary>
-        ///     Gets or sets the will delay interval.
+    ///     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
+        {
+            // 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.");
+        }
+
+        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.");
+            }
+
+            return ExchangeEnhancedAuthenticationResultFactory.Create(responseAuthPacket);
+        }
+
+        if (responsePacket is MqttDisconnectPacket disconnectPacket)
+        {
+            return ExchangeEnhancedAuthenticationResultFactory.Create(disconnectPacket);
+        }
+
+        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

@@ -8,11 +8,11 @@ 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();
-    {
-        readonly List<MqttTcpServerListener> _listeners = new List<MqttTcpServerListener>();
 
     CancellationTokenSource _cancellationTokenSource;
 
@@ -121,5 +121,4 @@ namespace MQTTnet.Server.Internal.Adapter
             }
         }
     }
-    }
 }

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

@@ -12,10 +12,10 @@ 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;
@@ -151,8 +151,7 @@ namespace MQTTnet.Server.Internal.Adapter
             {
                 if (exception is SocketException socketException)
                 {
-                        if (socketException.SocketErrorCode == SocketError.ConnectionAborted ||
+                    if (socketException.SocketErrorCode is SocketError.ConnectionAborted or SocketError.OperationAborted)
-                            socketException.SocketErrorCode == SocketError.OperationAborted)
                     {
                         continue;
                     }
@@ -166,12 +165,12 @@ namespace MQTTnet.Server.Internal.Adapter
 
     async Task TryHandleClientConnectionAsync(CrossPlatformSocket clientSocket)
     {
-            Stream stream = null;
+        Stream? stream = null;
-            string remoteEndPoint = null;
+        EndPoint? remoteEndPoint = null;
 
         try
         {
-                remoteEndPoint = clientSocket.RemoteEndPoint.ToString();
+            remoteEndPoint = clientSocket.RemoteEndPoint;
 
             _logger.Verbose("TCP client '{0}' accepted (Local endpoint={1})", remoteEndPoint, _localEndPoint);
 
@@ -216,13 +215,11 @@ namespace MQTTnet.Server.Internal.Adapter
                 var bufferWriter = new MqttBufferWriter(_serverOptions.WriterBufferSize, _serverOptions.WriterBufferSizeMax);
                 var packetFormatterAdapter = new MqttPacketFormatterAdapter(bufferWriter);
 
-                    using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger))
+                using var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger);
-                    {
                 clientAdapter.AllowPacketFragmentation = _options.AllowPacketFragmentation;
                 await clientHandler(clientAdapter).ConfigureAwait(false);
             }
         }
-            }
         catch (Exception exception)
         {
             if (exception is ObjectDisposedException)
@@ -243,8 +240,11 @@ namespace MQTTnet.Server.Internal.Adapter
         {
             try
             {
-                    // ReSharper disable once MethodHasAsyncOverload
+                if (stream != null)
-                    stream?.Dispose();
+                {
+                    await stream.DisposeAsync().ConfigureAwait(false);
+                }
+
                 clientSocket?.Dispose();
             }
             catch (Exception disposeException)
@@ -255,5 +255,4 @@ namespace MQTTnet.Server.Internal.Adapter
 
         _logger.Verbose("TCP client '{0}' disconnected (Local endpoint={1})", remoteEndPoint, _localEndPoint);
     }
-    }
 }

Source/MQTTnet.Server/Internal/CheckSubscriptionsResult.cs

@@ -4,10 +4,10 @@
 
 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 bool IsSubscribed { get; set; }
@@ -17,5 +17,4 @@ namespace MQTTnet.Server.Internal
     public List<uint> SubscriptionIdentifiers { get; set; }
 
     public MqttQualityOfServiceLevel QualityOfServiceLevel { get; set; }
-    }
 }

Source/MQTTnet.Server/Internal/DispatchApplicationMessageResult.cs

@@ -4,10 +4,10 @@
 
 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)
     {
         ReasonCode = reasonCode;
@@ -23,5 +23,4 @@ namespace MQTTnet.Server.Internal
     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
-    }
 }

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

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