Validate MQTT 5 SUBSCRIBE identifiers (#2262)

Observe packet task failures to prevent unobserved overflow exceptions

Server dispatch and session enqueue operations create packet bus items without
waiting for delivery. When the pending-message queue overflows, Fail faults
the item's completion task, which can later raise UnobservedTaskException
even if the application handles the dropped-message notification.

Observe the completion task's exception inside MqttPacketBusItem.Fail. This
keeps the task faulted and preserves the original exception for existing and
future WaitAsync callers, including DeliverApplicationMessageAsync.

Add a garbage-collection regression test for failures without a waiter and
verify that requesting the task before or after failure preserves the original
overflow exception. Re-enable unobserved-exception tracking in the existing
overflow integration tests for both drop strategies.

Before the fix, the focused run failed the new unobserved-exception test and
both enqueue overflow tests. After the fix, all nine focused cases and all
489 tests in the .NET 10 Release test suite pass.

Fixes https://github.com/dotnet/MQTTnet/issues/2271

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ name: CI
 on: [push, pull_request]
 
 env:
-  VERSION: "5.1.0.${{github.run_number}}"
+  VERSION: "5.2.0.${{github.run_number}}"
   PACKAGE_SUFFIX: ""
 
 jobs:
@@ -17,19 +17,26 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
+            10.0.x
 
       - name: Checkout code
         uses: actions/checkout@v4
 
       - name: Load strong name certificate
+        if: ${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
         run: |
           echo "$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 }} /p:SignAssembly=true /p:AssemblyOriginatorKeyFile=${{ github.workspace }}/certificate.snk
+      - name: Build package (signed)
+        if: ${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
+        run: dotnet build MQTTnet.slnx --configuration Release /p:FileVersion=${{ env.VERSION }} /p:AssemblyVersion=${{ env.VERSION }} /p:PackageVersion=${{ env.VERSION }}${{ env.PACKAGE_SUFFIX }} /p:SignAssembly=true /p:AssemblyOriginatorKeyFile=${{ github.workspace }}/certificate.snk
+
+      - name: Build package (unsigned)
+        if: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository }}
+        run: dotnet build MQTTnet.slnx --configuration Release /p:FileVersion=${{ env.VERSION }} /p:AssemblyVersion=${{ env.VERSION }} /p:PackageVersion=${{ env.VERSION }}${{ env.PACKAGE_SUFFIX }}
 
       - name: Upload nuget packages
         uses: actions/upload-artifact@v4
@@ -48,24 +55,19 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
+            10.0.x
 
       - name: Checkout code
         uses: actions/checkout@v4
 
       - name: Execute tests
-        run: dotnet test --framework net8.0 --configuration Release Source/MQTTnet.Tests/MQTTnet.Tests.csproj
+        run: dotnet test --framework net10.0 --configuration Release --project Source/MQTTnet.Tests/MQTTnet.Tests.csproj
 
   sign:
     needs: build
     runs-on: windows-latest # Code signing must run on a Windows agent for Authenticode signing (dll/exe)
-    if: github.repository == 'dotnet/MQTTnet'
+    if: github.repository == 'dotnet/MQTTnet' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository)
     steps:
-      - name: Setup .NET SDK
-        uses: actions/setup-dotnet@v4
-        with:
-          dotnet-version: |
-            6.0.x
-
       - name: Download nuget packages
         uses: actions/download-artifact@v4
         with:
@@ -73,7 +75,7 @@ jobs:
           path: nugets
 
       - name: Install sign CLI tool
-        run: dotnet tool install --tool-path . sign --version 0.9.0-beta.23127.3
+        run: dotnet tool install --tool-path . sign --version 0.9.1-beta.25379.1
 
       - name: Sign nugets
         shell: pwsh
@@ -114,7 +116,7 @@ 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:
-    # Tag schema is 'v5.0.0-rc' etc.
+    # Tag schema is 'v5.1.0-rc' etc.
     if: startsWith(github.ref, 'refs/tags/v')
     needs: [sign, test]
     runs-on: ubuntu-latest

Directory.Build.props

@@ -1,9 +1,34 @@
 <Project>
+    <PropertyGroup>
+        <TargetFrameworks>net8.0;net10.0</TargetFrameworks>
+        <Product>MQTTnet</Product>
+        <Authors>The contributors of MQTTnet</Authors>
+        <Company>The contributors of MQTTnet</Company>
+        <Copyright>Copyright (c) .NET Foundation and Contributors</Copyright>
 
-  <PropertyGroup>
-    <TestingPlatformShowTestsFailure>true</TestingPlatformShowTestsFailure>
-    <TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>
-    <EnableMSTestRunner>true</EnableMSTestRunner>
-  </PropertyGroup>
+        <DelaySign>false</DelaySign>
+        <SignAssembly>false</SignAssembly>
+        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>disable</Nullable>
 
-</Project>
+        <NeutralLanguage>en-US</NeutralLanguage>
+        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902</NoWarn>
+
+        <NuGetAuditMode>all</NuGetAuditMode>
+        <NuGetAudit>true</NuGetAudit>
+        <NuGetAuditLevel>low</NuGetAuditLevel>
+
+        <EnableNETAnalyzers>true</EnableNETAnalyzers>
+        <AnalysisLevel>latest</AnalysisLevel>
+        <AnalysisMode>recommended</AnalysisMode>
+        <AnalysisModeStyle>default</AnalysisModeStyle>
+    </PropertyGroup>
+
+    <PropertyGroup Condition="'$(GITHUB_ACTIONS)'=='true'">
+        <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
+    </PropertyGroup>
+
+</Project>

Directory.Build.targets

@@ -0,0 +1,24 @@
+<Project>
+
+    <PropertyGroup Condition="'$(GeneratePackageOnBuild)'=='true'">
+        <PackageLicenseFile>LICENSE</PackageLicenseFile>
+        <PackageIcon>nuget.png</PackageIcon>
+        <PackageProjectUrl>https://github.com/dotnet/MQTTnet</PackageProjectUrl>
+        <RepositoryUrl>https://github.com/dotnet/MQTTnet.git</RepositoryUrl>
+        <RepositoryType>git</RepositoryType>
+        <IncludeSymbols>true</IncludeSymbols>
+        <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+        <PublishRepositoryUrl>true</PublishRepositoryUrl>
+        <EmbedUntrackedSources>true</EmbedUntrackedSources>
+    </PropertyGroup>
+
+    <ItemGroup Condition="'$(GeneratePackageOnBuild)'=='true'">
+        <None Include="README.md" Pack="true" PackagePath="" Condition="Exists('README.md')" />
+        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
+        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
+    </ItemGroup>
+
+    <ItemGroup Condition="'$(IncludeSymbols)'=='true'">
+        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All"/>
+    </ItemGroup>
+</Project>

MQTTnet.sln

@@ -1,90 +0,0 @@
-
-Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 17
-VisualStudioVersion = 17.0.31919.166
-MinimumVisualStudioVersion = 10.0.40219.1
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet", "Source\MQTTnet\MQTTnet.csproj", "{3587E506-55A2-4EB3-99C7-DC01E42D25D2}"
-EndProject
-Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{B3F60ECB-45BA-4C66-8903-8BB89CA67998}"
-	ProjectSection(SolutionItems) = preProject
-		CODE-OF-CONDUCT.md = CODE-OF-CONDUCT.md
-		LICENSE = LICENSE
-		README.md = README.md
-		Source\ReleaseNotes.md = Source\ReleaseNotes.md
-		.github\workflows\ci.yml = .github\workflows\ci.yml
-	EndProjectSection
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.AspNetCore", "Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj", "{F10C4060-F7EE-4A83-919F-FF723E72F94A}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Extensions.Rpc", "Source\MQTTnet.Extensions.Rpc\MQTTnet.Extensions.Rpc.csproj", "{C444E9C8-95FA-430E-9126-274129DE16CD}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Samples", "Samples\MQTTnet.Samples.csproj", "{71CF35F5-3327-4A91-AAF4-5340F6701771}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Tests", "Source\MQTTnet.Tests\MQTTnet.Tests.csproj", "{B270F32A-9F3E-42EE-A989-813E35E29ADB}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Benchmarks", "Source\MQTTnet.Benchmarks\MQTTnet.Benchmarks.csproj", "{2F516E76-AAC4-4219-B7D1-34CDD3CFF381}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.TestApp", "Source\MQTTnet.TestApp\MQTTnet.TestApp.csproj", "{175D5340-CC5B-4542-939D-4E7D15A0BC8D}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.AspTestApp", "Source\MQTTnet.AspTestApp\MQTTnet.AspTestApp.csproj", "{72867E4C-4E15-4E8E-8FAB-AE9253286BBC}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Extensions.TopicTemplate", "Source\MQTTnet.Extensions.TopicTemplate\MQTTnet.Extensions.TopicTemplate.csproj", "{374D5861-F7A6-42A2-8CBE-040846000EF9}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.Server", "Source\MQTTnet.Server\MQTTnet.Server.csproj", "{C876EFFD-C5AD-4E26-BD9F-4C48252C02BC}"
-EndProject
-Global
-	GlobalSection(SolutionConfigurationPlatforms) = preSolution
-		Debug|Any CPU = Debug|Any CPU
-		Release|Any CPU = Release|Any CPU
-	EndGlobalSection
-	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|Any CPU.Build.0 = Release|Any CPU
-		{F10C4060-F7EE-4A83-919F-FF723E72F94A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{F10C4060-F7EE-4A83-919F-FF723E72F94A}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{F10C4060-F7EE-4A83-919F-FF723E72F94A}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{F10C4060-F7EE-4A83-919F-FF723E72F94A}.Release|Any CPU.Build.0 = Release|Any CPU
-		{C444E9C8-95FA-430E-9126-274129DE16CD}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{C444E9C8-95FA-430E-9126-274129DE16CD}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{C444E9C8-95FA-430E-9126-274129DE16CD}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{C444E9C8-95FA-430E-9126-274129DE16CD}.Release|Any CPU.Build.0 = Release|Any CPU
-		{71CF35F5-3327-4A91-AAF4-5340F6701771}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{71CF35F5-3327-4A91-AAF4-5340F6701771}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{71CF35F5-3327-4A91-AAF4-5340F6701771}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{71CF35F5-3327-4A91-AAF4-5340F6701771}.Release|Any CPU.Build.0 = Release|Any CPU
-		{B270F32A-9F3E-42EE-A989-813E35E29ADB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{B270F32A-9F3E-42EE-A989-813E35E29ADB}.Debug|Any CPU.Build.0 = Debug|Any CPU
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-		{2F516E76-AAC4-4219-B7D1-34CDD3CFF381}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{2F516E76-AAC4-4219-B7D1-34CDD3CFF381}.Release|Any CPU.Build.0 = Release|Any CPU
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-		{175D5340-CC5B-4542-939D-4E7D15A0BC8D}.Release|Any CPU.Build.0 = Release|Any CPU
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-		{374D5861-F7A6-42A2-8CBE-040846000EF9}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{374D5861-F7A6-42A2-8CBE-040846000EF9}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{374D5861-F7A6-42A2-8CBE-040846000EF9}.Release|Any CPU.Build.0 = Release|Any CPU
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-		{C876EFFD-C5AD-4E26-BD9F-4C48252C02BC}.Release|Any CPU.ActiveCfg = Release|Any CPU
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-		HideSolutionNode = FALSE
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MQTTnet.slnx

@@ -0,0 +1,28 @@
+<Solution>
+  <Configurations>
+    <Platform Name="Any CPU" />
+    <Platform Name="x64" />
+    <Platform Name="x86" />
+  </Configurations>
+  <Folder Name="/Solution Items/">
+    <File Path=".github/workflows/ci.yml" />
+    <File Path="CODE-OF-CONDUCT.md" />
+    <File Path="Directory.Build.props" />
+    <File Path="Directory.Build.targets" />
+    <File Path="LICENSE" />
+    <File Path="README.md" />
+    <File Path="Source/ReleaseNotes.md" />
+  </Folder>
+  <Project Path="Samples/MQTTnet.Samples.csproj" />
+  <Project Path="Source/MQTTnet.AspnetCore/MQTTnet.AspNetCore.csproj" />
+  <Project Path="Source/MQTTnet.AspTestApp/MQTTnet.AspTestApp.csproj" />
+  <Project Path="Source/MQTTnet.Benchmarks/MQTTnet.Benchmarks.csproj" />
+  <Project Path="Source/MQTTnet.Extensions.Rpc/MQTTnet.Extensions.Rpc.csproj" />
+  <Project Path="Source/MQTTnet.Extensions.Socks5/MQTTnet.Extensions.Socks5.csproj" />
+  <Project Path="Source/MQTTnet.Extensions.TopicTemplate/MQTTnet.Extensions.TopicTemplate.csproj" />
+  <Project Path="Source/MQTTnet.Server/MQTTnet.Server.csproj" />
+  <Project Path="Source/MQTTnet.TestApp/MQTTnet.TestApp.csproj" />
+  <Project Path="Source/MQTTnet.Tests.Extensions.Socks5/MQTTnet.Tests.Extensions.Socks5.csproj" />
+  <Project Path="Source/MQTTnet.Tests/MQTTnet.Tests.csproj" />
+  <Project Path="Source/MQTTnet/MQTTnet.csproj" />
+</Solution>

README.md

@@ -12,9 +12,9 @@
 
 # MQTTnet
 
-MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (
-broker) and supports the MQTT protocol up to version 5. It is compatible with mostly any supported .NET Framework
-version and CPU architecture.
+MQTTnet is a high performance .NET library for MQTT based communication.
+It provides a MQTT client and a MQTT server (broker) and supports the MQTT protocol up to version 5.
+It is compatible with mostly any supported .NET Framework version and CPU architecture.
 
 ## Features
 

Samples/Client/Client_Connection_Samples.cs

@@ -490,7 +490,7 @@ m/XriWr/Cq4h/JfB7NTsezVslgkBaoU=
         }
     }
 
-    class SampleClientKerberosAuthenticationHandler : IMqttEnhancedAuthenticationHandler
+    sealed class SampleClientKerberosAuthenticationHandler : IMqttEnhancedAuthenticationHandler
     {
         public async Task HandleEnhancedAuthenticationAsync(MqttEnhancedAuthenticationEventArgs eventArgs)
         {

Samples/Client/Client_Publish_Samples.cs

@@ -6,6 +6,9 @@
 // ReSharper disable UnusedMember.Global
 // ReSharper disable InconsistentNaming
 
+using System;
+using System.Text;
+
 namespace MQTTnet.Samples.Client;
 
 public static class Client_Publish_Samples
@@ -84,4 +87,21 @@ public static class Client_Publish_Samples
 
         Console.WriteLine("MQTT application message is published.");
     }
+
+    public static MqttApplicationMessage Create_Message_With_Binary_User_Property()
+    {
+        /*
+         * MQTT v5 user properties are encoded as UTF-8 strings. When the UTF-8 payload is already available
+         * as a byte buffer, the builder APIs can avoid creating intermediate strings.
+         */
+
+        var encodedValue = Encoding.UTF8.GetBytes("sensor-01");
+
+        return new MqttApplicationMessageBuilder()
+            .WithTopic("samples/metadata/binary")
+            .WithUserProperty("client-id", encodedValue.AsMemory())
+            .WithUserProperty("checksum", new ArraySegment<byte>(encodedValue))
+            .WithPayload("metadata")
+            .Build();
+    }
 }

Samples/Client/Client_Socks5_Samples.cs

@@ -0,0 +1,86 @@
+// 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.
+
+// ReSharper disable UnusedType.Global
+// ReSharper disable UnusedMember.Global
+// ReSharper disable InconsistentNaming
+
+using MQTTnet.Extensions.Socks5;
+using MQTTnet.Samples.Helpers;
+
+namespace MQTTnet.Samples.Client;
+
+public static class Client_Socks5_Samples
+{
+    public static async Task Connect_Tcp_Via_Socks5_No_Auth()
+    {
+        /*
+         * This sample connects to an MQTT broker through a SOCKS5 proxy that does not
+         * require authentication. The SOCKS5 stream provider performs the proxy handshake
+         * (RFC 1928) and returns a connected stream that the MQTT TCP channel can use as if
+         * it were a direct TCP connection.
+         *
+         * Host name resolution is performed by the proxy by default (ATYP=DOMAINNAME), which
+         * is the desired behavior when the MQTT broker hostname is only reachable from inside
+         * the network the proxy lives in.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+
+        var mqttClientOptions = new MqttClientOptionsBuilder()
+            .WithTcpServer("broker.internal.example", 1883)
+            .WithSocks5Proxy(socks => socks
+                .WithHost("proxy.example.com")
+                .WithPort(1080))
+            .Build();
+
+        using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(15));
+        var response = await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
+
+        Console.WriteLine("The MQTT client is connected through SOCKS5.");
+        response.DumpToConsole();
+
+        var disconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder().Build();
+        await mqttClient.DisconnectAsync(disconnectOptions, CancellationToken.None);
+    }
+
+    public static async Task Connect_Tcp_With_Tls_Via_Socks5_With_Credentials()
+    {
+        /*
+         * This sample connects to a TLS-protected MQTT broker through a SOCKS5 proxy that
+         * requires username/password authentication (RFC 1929).
+         *
+         * Note that the TLS handshake is layered on top of the SOCKS5 tunnel: the SNI used
+         * by SslStream is derived from the broker hostname (or the value passed to
+         * WithTargetHost), not from the proxy hostname.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+
+        var mqttClientOptions = new MqttClientOptionsBuilder()
+            .WithTcpServer("broker.internal.example", 8883)
+            .WithTlsOptions(tls => tls
+                .WithTargetHost("broker.internal.example"))
+            .WithSocks5Proxy(socks => socks
+                .WithHost("proxy.example.com")
+                .WithPort(1080)
+                .WithCredentials("alice", "s3cr3t")
+                .WithResolveDnsRemotely(true)
+                .WithHandshakeTimeout(TimeSpan.FromSeconds(10)))
+            .Build();
+
+        using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(15));
+        var response = await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
+
+        Console.WriteLine("The MQTT client is connected through SOCKS5 with TLS.");
+        response.DumpToConsole();
+
+        var disconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder().Build();
+        await mqttClient.DisconnectAsync(disconnectOptions, CancellationToken.None);
+    }
+}

Samples/Client/Client_Subscribe_Samples.cs

@@ -7,7 +7,7 @@
 // ReSharper disable InconsistentNaming
 // ReSharper disable UnusedMember.Local
 
-using MQTTnet.Extensions.TopicTemplate;
+using System.Text;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 using MQTTnet.Samples.Helpers;
@@ -16,8 +16,6 @@ namespace MQTTnet.Samples.Client;
 
 public static class Client_Subscribe_Samples
 {
-    static readonly MqttTopicTemplate sampleTemplate = new("mqttnet/samples/topic/{id}");
-
     public static async Task Handle_Received_Application_Message()
     {
         /*
@@ -42,7 +40,7 @@ public static class Client_Subscribe_Samples
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "2")).Build();
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicFilter("mqttnet/samples/topic/2").Build();
 
         await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
@@ -55,7 +53,7 @@ public static class Client_Subscribe_Samples
     public static async Task Send_Responses()
     {
         /*
-         * This sample subscribes to a topic and sends a response to the broker. This requires at least QoS level 1 to work!
+         * This sample subscribes to a topic and sends a detailed response to the client. This requires at least QoS level 1 to work!
          */
 
         var mqttFactory = new MqttClientFactory();
@@ -70,7 +68,7 @@ public static class Client_Subscribe_Samples
             args.ResponseReasonString = "That did not work!";
 
             // User properties require MQTT v5!
-            args.ResponseUserProperties.Add(new MqttUserProperty("My", "Data"));
+            args.ResponseUserProperties.Add(new MqttUserProperty("My", Encoding.UTF8.GetBytes("Data")));
 
             // Now the broker will resend the message again.
             return Task.CompletedTask;
@@ -80,7 +78,7 @@ public static class Client_Subscribe_Samples
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "1")).Build();
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicFilter("topic/test").Build();
 
         var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
@@ -106,9 +104,10 @@ public static class Client_Subscribe_Samples
         // Create the subscribe options including several topics with different options.
         // It is also possible to all of these topics using a dedicated call of _SubscribeAsync_ per topic.
         var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
-            .WithTopicTemplate(sampleTemplate.WithParameter("id", "1"))
-            .WithTopicTemplate(sampleTemplate.WithParameter("id", "2"), noLocal: true)
-            .WithTopicTemplate(sampleTemplate.WithParameter("id", "3"), retainHandling: MqttRetainHandling.SendAtSubscribe)
+            .WithTopicFilter(t => t.WithTopic("topic/1").WithAtLeastOnceQoS())
+            .WithTopicFilter(t => t.WithTopic("topic/2").WithAtMostOnceQoS())
+            .WithTopicFilter(t => t.WithTopic("topic/3").WithNoLocal())
+            .WithTopicFilter(t => t.WithRetainHandling(MqttRetainHandling.SendAtSubscribe))
             .Build();
 
         var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
@@ -132,7 +131,9 @@ public static class Client_Subscribe_Samples
 
         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
 
-        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(sampleTemplate.WithParameter("id", "1")).Build();
+        var topicFilter = mqttFactory.CreateTopicFilterBuilder().WithTopic("mqttnet/samples/topic/2").WithAtLeastOnceQoS();
+
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicFilter(topicFilter).Build();
 
         var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
 
@@ -142,7 +143,7 @@ public static class Client_Subscribe_Samples
         response.DumpToConsole();
     }
 
-    static void ConcurrentProcessingDisableAutoAcknowledge(CancellationToken shutdownToken, IMqttClient mqttClient)
+    static void ConcurrentProcessingDisableAutoAcknowledge(IMqttClient mqttClient, CancellationToken shutdownToken)
     {
         /*
          * This sample shows how to achieve concurrent processing and not have message AutoAcknowledged
@@ -170,7 +171,7 @@ public static class Client_Subscribe_Samples
         };
     }
 
-    static void ConcurrentProcessingWithLimit(CancellationToken shutdownToken, IMqttClient mqttClient)
+    static void ConcurrentProcessingWithLimit(IMqttClient mqttClient, CancellationToken shutdownToken)
     {
         /*
          * This sample shows how to achieve concurrent processing, with:

Samples/Client/Client_Subscribe_TopicTemplate_Samples.cs

@@ -0,0 +1,75 @@
+// 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.Extensions.TopicTemplate;
+using MQTTnet.Protocol;
+using MQTTnet.Samples.Helpers;
+
+// ReSharper disable UnusedType.Global
+// ReSharper disable UnusedMember.Global
+// ReSharper disable InconsistentNaming
+// ReSharper disable UnusedMember.Local
+
+namespace MQTTnet.Samples.Client;
+
+public static class Client_Subscribe_TopicTemplate_Samples
+{
+    static readonly MqttTopicTemplate SampleTemplate = new("mqttnet/samples/topic/{id}");
+
+    public static async Task Subscribe_Multiple_Topics_With_Template()
+    {
+        /*
+         * This sample subscribes to several topics in a single request.
+         *
+         * This sample requires the nuget 'MQTTnet.Extensions.TopicTemplate'.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        // Create the subscribe options including several topics with different options.
+        // It is also possible to all of these topics using a dedicated call of _SubscribeAsync_ per topic.
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
+            .WithTopicTemplate(SampleTemplate.WithParameter("id", "1"))
+            .WithTopicTemplate(SampleTemplate.WithParameter("id", "2"), noLocal: true)
+            .WithTopicTemplate(SampleTemplate.WithParameter("id", "3"), retainHandling: MqttRetainHandling.SendAtSubscribe)
+            .Build();
+
+        var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+
+        Console.WriteLine("MQTT client subscribed to topics.");
+
+        // The response contains additional data sent by the server after subscribing.
+        response.DumpToConsole();
+    }
+
+    public static async Task Subscribe_Topic_With_Template()
+    {
+        /*
+         * This sample subscribes to a topic.
+         *
+         * This sample requires the nuget 'MQTTnet.Extensions.TopicTemplate'.
+         */
+
+        var mqttFactory = new MqttClientFactory();
+
+        using var mqttClient = mqttFactory.CreateMqttClient();
+        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();
+
+        await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
+
+        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder().WithTopicTemplate(SampleTemplate.WithParameter("id", "1")).Build();
+
+        var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
+
+        Console.WriteLine("MQTT client subscribed to topic.");
+
+        // The response contains additional data sent by the server after subscribing.
+        response.DumpToConsole();
+    }
+}

Samples/Diagnostics/Logger_Samples.cs

@@ -6,6 +6,7 @@
 // ReSharper disable UnusedMember.Global
 // ReSharper disable InconsistentNaming
 
+using System.Globalization;
 using System.Text;
 using MQTTnet.Diagnostics.Logger;
 
@@ -51,7 +52,7 @@ public static class Logger_Samples
         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}");
+            output.AppendLine(CultureInfo.InvariantCulture, $">> [{args.LogMessage.Timestamp:O}] [{args.LogMessage.ThreadId}] [{args.LogMessage.Source}] [{args.LogMessage.Level}]: {args.LogMessage.Message}");
             if (args.LogMessage.Exception != null)
             {
                 output.AppendLine(args.LogMessage.Exception.ToString());

Samples/Helpers/ObjectExtensions.cs

@@ -8,17 +8,19 @@ namespace MQTTnet.Samples.Helpers;
 
 internal static class ObjectExtensions
 {
+    static readonly JsonSerializerOptions SerializerOptions = new()
+    {
+        WriteIndented = true
+    };
+
     public static TObject DumpToConsole<TObject>(this TObject @object)
     {
         var output = "NULL";
         if (@object != null)
         {
-            output = JsonSerializer.Serialize(@object, new JsonSerializerOptions
-            {
-                WriteIndented = true
-            });
+            output = JsonSerializer.Serialize(@object, SerializerOptions);
         }
-        
+
         Console.WriteLine($"[{@object?.GetType().Name}]:\r\n{output}");
         return @object;
     }

Samples/MQTTnet.Samples.csproj

@@ -2,26 +2,17 @@
 
     <PropertyGroup>
         <OutputType>Exe</OutputType>
-        <TargetFramework>net8.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <IsPackable>false</IsPackable>
-        <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
-        <EnableNETAnalyzers>false</EnableNETAnalyzers>
-        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902</NoWarn>
-        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-        <NuGetAuditMode>all</NuGetAuditMode>
-        <NuGetAudit>true</NuGetAudit>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <AnalysisLevel>latest-Recommended</AnalysisLevel>
-        <LangVersion>default</LangVersion>
+        <NoWarn>$(NoWarn);CA1707</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
 
         <ProjectReference Include="..\Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj"/>
         <ProjectReference Include="..\Source\MQTTnet.Extensions.Rpc\MQTTnet.Extensions.Rpc.csproj"/>
+        <ProjectReference Include="..\Source\MQTTnet.Extensions.Socks5\MQTTnet.Extensions.Socks5.csproj" />
         <ProjectReference Include="..\Source\MQTTnet.Extensions.TopicTemplate\MQTTnet.Extensions.TopicTemplate.csproj" />
         <ProjectReference Include="..\Source\MQTTnet.Server\MQTTnet.Server.csproj"/>
         <ProjectReference Include="..\Source\MQTTnet\MQTTnet.csproj"/>

Samples/Program.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Globalization;
 using System.Reflection;
 
 Console.BackgroundColor = ConsoleColor.White;
@@ -28,7 +29,7 @@ Console.Write("Please choose sample class (press Enter to continue): ");
 Console.ResetColor();
 
 var input = Console.ReadLine();
-var selectedIndex = int.Parse(input ?? "0");
+var selectedIndex = int.Parse(input ?? "0", CultureInfo.InvariantCulture);
 var selectedSampleClass = sampleClasses[selectedIndex];
 var sampleMethods = selectedSampleClass.GetMethods(BindingFlags.Static | BindingFlags.Public).OrderBy(m => m.Name).ToList();
 
@@ -45,7 +46,7 @@ Console.Write("Please choose sample (press Enter to continue): ");
 Console.ResetColor();
 
 input = Console.ReadLine();
-selectedIndex = int.Parse(input ?? "0");
+selectedIndex = int.Parse(input ?? "0", CultureInfo.InvariantCulture);
 var selectedSampleMethod = sampleMethods[selectedIndex];
 
 Console.WriteLine();
@@ -58,7 +59,7 @@ try
 {
     if (selectedSampleMethod.Invoke(null, null) is Task task)
     {
-        await task;    
+        await task;
     }
 }
 catch (Exception exception)

Samples/Server/Server_ASP_NET_Samples.cs

@@ -8,6 +8,7 @@
 // ReSharper disable EmptyConstructor
 // ReSharper disable MemberCanBeMadeStatic.Local
 
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.DependencyInjection;
@@ -52,14 +53,14 @@ public static class Server_ASP_NET_Samples
             // Inject other services via constructor.
         }
 
-        public Task OnClientConnected(ClientConnectedEventArgs eventArgs)
+        public static Task OnClientConnected(ClientConnectedEventArgs eventArgs)
         {
             Console.WriteLine($"Client '{eventArgs.ClientId}' connected.");
             return Task.CompletedTask;
         }
 
 
-        public Task ValidateConnection(ValidatingConnectionEventArgs eventArgs)
+        public static Task ValidateConnection(ValidatingConnectionEventArgs eventArgs)
         {
             Console.WriteLine($"Client '{eventArgs.ClientId}' wants to connect. Accepting!");
             return Task.CompletedTask;
@@ -68,6 +69,7 @@ public static class Server_ASP_NET_Samples
 
     sealed class Startup
     {
+        [SuppressMessage("Performance", "CA1822:Mark members as static")]
         public void Configure(IApplicationBuilder app, IWebHostEnvironment environment, MqttController mqttController)
         {
             app.UseRouting();
@@ -88,11 +90,12 @@ public static class Server_ASP_NET_Samples
                      * Attach event handlers etc. if required.
                      */
 
-                    server.ValidatingConnectionAsync += mqttController.ValidateConnection;
-                    server.ClientConnectedAsync += mqttController.OnClientConnected;
+                    server.ValidatingConnectionAsync += MqttController.ValidateConnection;
+                    server.ClientConnectedAsync += MqttController.OnClientConnected;
                 });
         }
 
+        [SuppressMessage("Performance", "CA1822:Mark members as static")]
         public void ConfigureServices(IServiceCollection services)
         {
             services.AddHostedMqttServer(

Samples/Server/Server_Intercepting_Samples.cs

@@ -9,6 +9,7 @@
 // ReSharper disable MemberCanBeMadeStatic.Local
 
 using MQTTnet.Internal;
+using MQTTnet.Protocol;
 using MQTTnet.Server;
 
 namespace MQTTnet.Samples.Server;
@@ -42,4 +43,32 @@ public static class Server_Intercepting_Samples
         Console.ReadLine();
         await mqttServer.StopAsync();
     }
+
+    public static async Task Intercept_Subscription()
+    {
+        /*
+         * This sample starts a simple MQTT server which does not allow to subscribe to '#'
+         * Start the server and try to subscribe to '#' with a client of choice.
+         */
+
+        var mqttServerFactory = new MqttServerFactory();
+        var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
+
+        using var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions);
+        mqttServer.InterceptingSubscriptionAsync += args =>
+        {
+            if (args.TopicFilter.Topic.Equals("#", StringComparison.Ordinal))
+            {
+                args.Response.ReasonCode = MqttSubscribeReasonCode.NotAuthorized;
+            }
+
+            return CompletedTask.Instance;
+        };
+
+        await mqttServer.StartAsync();
+
+        Console.WriteLine("Press Enter to exit.");
+        Console.ReadLine();
+        await mqttServer.StopAsync();
+    }
 }

Samples/Server/Server_Simple_Samples.cs

@@ -6,6 +6,7 @@
 // ReSharper disable UnusedMember.Global
 // ReSharper disable InconsistentNaming
 
+using System.Globalization;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Protocol;
 using MQTTnet.Server;
@@ -161,7 +162,7 @@ public static class Server_Simple_Samples
         return server;
     }
 
-    class ConsoleLogger : IMqttNetLogger
+    sealed class ConsoleLogger : IMqttNetLogger
     {
         readonly object _consoleSyncRoot = new();
 
@@ -191,7 +192,7 @@ public static class Server_Simple_Samples
 
             if (parameters?.Length > 0)
             {
-                message = string.Format(message, parameters);
+                message = string.Format(CultureInfo.InvariantCulture, message, parameters);
             }
 
             lock (_consoleSyncRoot)

Samples/Server/Server_TLS_Samples.cs

@@ -59,10 +59,12 @@ public static class Server_TLS_Samples
         certRequest.CertificateExtensions.Add(sanBuilder.Build());
 
         using var certificate = certRequest.CreateSelfSigned(DateTimeOffset.Now.AddMinutes(-10), DateTimeOffset.Now.AddMinutes(10));
+#pragma warning disable SYSLIB0057
         var pfxCertificate = new X509Certificate2(
             certificate.Export(X509ContentType.Pfx),
             (string)null!,
             X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.Exportable);
+#pragma warning restore SYSLIB0057
 
         return pfxCertificate;
     }

Source/MQTTnet.AspTestApp/MQTTnet.AspTestApp.csproj

@@ -1,19 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
         <Nullable>enable</Nullable>
         <ImplicitUsings>enable</ImplicitUsings>
         <IsPackable>false</IsPackable>
-        <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
-        <EnableNETAnalyzers>false</EnableNETAnalyzers>
-        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902</NoWarn>
-        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-        <NuGetAuditMode>all</NuGetAuditMode>
-        <NuGetAudit>true</NuGetAudit>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <AnalysisLevel>latest-Recommended</AnalysisLevel>
+        <NoWarn>$(NoWarn);CA1707</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>

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

@@ -6,7 +6,7 @@ using Microsoft.AspNetCore.Mvc.RazorPages;
 
 namespace MQTTnet.AspTestApp.Pages;
 
-public class IndexModel : PageModel
+public partial class IndexModel : PageModel
 {
     readonly ILogger<IndexModel> _logger;
 
@@ -17,6 +17,9 @@ public class IndexModel : PageModel
 
     public void OnGet()
     {
-        _logger.LogDebug("OnGet");
+        LogOnGet();
     }
+
+    [LoggerMessage(Level = LogLevel.Information, Message = "OnGet")]
+    private partial void LogOnGet();
 }

Source/MQTTnet.AspnetCore/ApplicationBuilderExtensions.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 Microsoft.AspNetCore.Builder;
 using Microsoft.Extensions.DependencyInjection;
 using MQTTnet.Server;

Source/MQTTnet.AspnetCore/AspNetMqttServerOptionsBuilder.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 MQTTnet.Server;
 
 namespace MQTTnet.AspNetCore;

Source/MQTTnet.AspnetCore/BufferExtensions.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.Runtime.InteropServices;
 
 namespace MQTTnet.AspNetCore;

Source/MQTTnet.AspnetCore/EndpointRouterExtensions.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 Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Routing;
 

Source/MQTTnet.AspnetCore/MQTTnet.AspNetCore.csproj

@@ -1,61 +1,23 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
         <AssemblyName>MQTTnet.AspNetCore</AssemblyName>
         <RootNamespace>MQTTnet.AspNetCore</RootNamespace>
-        <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
-        <Company>The contributors of MQTTnet</Company>
-        <Product>MQTTnet</Product>
-        <Description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</Description>
-        <Authors>The contributors of MQTTnet</Authors>
-        <PackageId>MQTTnet.AspNetCore</PackageId>
-        <SignAssembly>false</SignAssembly>
-        <DelaySign>false</DelaySign>
-        <PublishRepositoryUrl>true</PublishRepositoryUrl>
-        <IncludeSymbols>true</IncludeSymbols>
-        <SymbolPackageFormat>snupkg</SymbolPackageFormat>
-        <Copyright>Copyright (c) .NET Foundation and Contributors</Copyright>
-        <PackageProjectUrl>https://github.com/dotnet/MQTTnet</PackageProjectUrl>
-        <RepositoryUrl>https://github.com/dotnet/MQTTnet.git</RepositoryUrl>
-        <RepositoryType>git</RepositoryType>
-        <PackageTags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin Blazor</PackageTags>
-        <NeutralLanguage>en-US</NeutralLanguage>
-        <EnableNETAnalyzers>false</EnableNETAnalyzers>
-        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <PackageIcon>nuget.png</PackageIcon>
-        <EmbedUntrackedSources>true</EmbedUntrackedSources>
-        <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <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>
-        <GenerateDocumentationFile>true</GenerateDocumentationFile>
-        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902</NoWarn>
-        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-        <NuGetAuditMode>all</NuGetAuditMode>
-        <NuGetAudit>true</NuGetAudit>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <AnalysisLevel>latest-Recommended</AnalysisLevel>
         <IsAotCompatible>true</IsAotCompatible>
-        <LangVersion>default</LangVersion>
-        <Nullable>enable</Nullable>
+
+        <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+        <Description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</Description>
+        <PackageId>MQTTnet.AspNetCore</PackageId>
+        <PackageTags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin Blazor</PackageTags>
+        <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
+
+        <GenerateDocumentationFile>true</GenerateDocumentationFile>
     </PropertyGroup>
 
     <ItemGroup>
-        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
-    </ItemGroup>
-
-    <ItemGroup>
-        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All"/>
         <FrameworkReference Include="Microsoft.AspNetCore.App"/>
     </ItemGroup>
 
-    <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release'">
-    </PropertyGroup>
-
     <ItemGroup>
         <ProjectReference Include="..\MQTTnet.Server\MQTTnet.Server.csproj"/>
         <ProjectReference Include="..\MQTTnet\MQTTnet.csproj"/>

Source/MQTTnet.AspnetCore/MqttClientConnectionContextFactory.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 MQTTnet.Adapter;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Formatter;
@@ -13,7 +12,7 @@ public sealed class MqttClientConnectionContextFactory : IMqttClientAdapterFacto
 {
     public IMqttChannelAdapter CreateClientAdapter(MqttClientOptions options, MqttPacketInspector packetInspector, IMqttNetLogger logger)
     {
-        if (options == null) throw new ArgumentNullException(nameof(options));
+        ArgumentNullException.ThrowIfNull(options);
 
         switch (options.ChannelOptions)
         {

Source/MQTTnet.AspnetCore/MqttConnectionContext.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;
 using System.Buffers;
 using System.IO.Pipelines;
 using System.Net;
 using System.Security.Cryptography.X509Certificates;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Http.Connections.Features;
 using Microsoft.AspNetCore.Http.Features;
@@ -61,27 +58,6 @@ public sealed class MqttConnectionContext : IMqttChannelAdapter
         }
     }
 
-    public EndPoint RemoteEndPoint
-    {
-        get
-        {
-            // mqtt over tcp
-            if (_connection.RemoteEndPoint != null)
-            {
-                return _connection.RemoteEndPoint;
-            }
-
-            // mqtt over websocket
-            var httpFeature = _connection.Features.Get<IHttpConnectionFeature>();
-            if (httpFeature?.RemoteIpAddress != null)
-            {
-                return new IPEndPoint(httpFeature.RemoteIpAddress, httpFeature.RemotePort);
-            }
-
-            return null;
-        }
-    }
-
     public bool IsSecureConnection
     {
         get
@@ -104,8 +80,50 @@ public sealed class MqttConnectionContext : IMqttChannelAdapter
         }
     }
 
+    public EndPoint LocalEndPoint
+    {
+        get
+        {
+            // mqtt over tcp
+            if (_connection.LocalEndPoint != null)
+            {
+                return _connection.LocalEndPoint;
+            }
+
+            // mqtt over websocket
+            var httpFeature = _connection.Features.Get<IHttpConnectionFeature>();
+            if (httpFeature?.LocalIpAddress != null)
+            {
+                return new IPEndPoint(httpFeature.LocalIpAddress, httpFeature.LocalPort);
+            }
+
+            return null;
+        }
+    }
+
     public MqttPacketFormatterAdapter PacketFormatterAdapter { get; }
 
+    public EndPoint RemoteEndPoint
+    {
+        get
+        {
+            // mqtt over tcp
+            if (_connection.RemoteEndPoint != null)
+            {
+                return _connection.RemoteEndPoint;
+            }
+
+            // mqtt over websocket
+            var httpFeature = _connection.Features.Get<IHttpConnectionFeature>();
+            if (httpFeature?.RemoteIpAddress != null)
+            {
+                return new IPEndPoint(httpFeature.RemoteIpAddress, httpFeature.RemotePort);
+            }
+
+            return null;
+        }
+    }
+
     public async Task ConnectAsync(CancellationToken cancellationToken)
     {
         if (_connection is SocketConnection tcp && !tcp.IsConnected)
@@ -232,8 +250,8 @@ public sealed class MqttConnectionContext : IMqttChannelAdapter
         var span = output.GetSpan(buffer.Length);
 
         buffer.Packet.AsSpan().CopyTo(span);
-        int offset = buffer.Packet.Count;
-        buffer.Payload.CopyTo(destination: span.Slice(offset));
+        var offset = buffer.Packet.Count;
+        buffer.Payload.CopyTo(span.Slice(offset));
         output.Advance(buffer.Length);
     }
 }

Source/MQTTnet.AspnetCore/MqttConnectionHandler.cs

@@ -2,8 +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.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Connections.Features;
 using MQTTnet.Adapter;

Source/MQTTnet.AspnetCore/MqttHostedServer.cs

@@ -2,10 +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.Collections.Generic;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.Extensions.Hosting;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Server;

Source/MQTTnet.AspnetCore/MqttSubProtocolSelector.cs

@@ -2,9 +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.Collections.Generic;
-using System.Linq;
 using Microsoft.AspNetCore.Http;
 
 namespace MQTTnet.AspNetCore;
@@ -29,6 +26,6 @@ public static class MqttSubProtocolSelector
         ArgumentNullException.ThrowIfNull(requestedSubProtocolValues);
 
         // Order the protocols to also match "mqtt", "mqttv-3.1", "mqttv-3.11" etc.
-        return requestedSubProtocolValues.OrderByDescending(p => p.Length).FirstOrDefault(p => p.ToLower().StartsWith("mqtt"));
+        return requestedSubProtocolValues.OrderByDescending(p => p.Length).FirstOrDefault(p => p.ToLowerInvariant().StartsWith("mqtt", StringComparison.InvariantCulture));
     }
 }

Source/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -2,10 +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.
 
-using System;
 using System.Net;
 using System.Net.WebSockets;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using MQTTnet.Adapter;
 using MQTTnet.Diagnostics.Logger;

Source/MQTTnet.AspnetCore/ReaderExtensions.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.Runtime.InteropServices;
 using MQTTnet.Adapter;

Source/MQTTnet.AspnetCore/ServiceCollectionExtensions.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 Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;

Source/MQTTnet.AspnetCore/SocketAwaitable.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;
 using System.Diagnostics;
 using System.IO.Pipelines;
 using System.Net.Sockets;
 using System.Runtime.CompilerServices;
-using System.Threading;
-using System.Threading.Tasks;
 
 namespace MQTTnet.AspNetCore;
 

Source/MQTTnet.AspnetCore/SocketConnection.cs

@@ -2,13 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
-using System.IO;
 using System.IO.Pipelines;
 using System.Net;
 using System.Net.Sockets;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Http.Features;
 using MQTTnet.Exceptions;
@@ -81,7 +77,7 @@ public sealed class SocketConnection : ConnectionContext
         IsConnected = true;
     }
 
-    static Exception ConnectionAborted()
+    static MqttCommunicationException ConnectionAborted()
     {
         return new MqttCommunicationException("Connection Aborted");
     }
@@ -218,12 +214,16 @@ public sealed class SocketConnection : ConnectionContext
 
             var flushTask = _application.Output.FlushAsync();
 
+            FlushResult result;
             if (!flushTask.IsCompleted)
             {
-                await flushTask;
+                result = await flushTask;
+            }
+            else
+            {
+                result = flushTask.GetAwaiter().GetResult();
             }
 
-            var result = flushTask.GetAwaiter().GetResult();
             if (result.IsCompleted)
             {
                 // Pipe consumer is shut down, do we stop writing

Source/MQTTnet.AspnetCore/SocketReceiver.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 System.IO.Pipelines;
 using System.Net.Sockets;
 
 namespace MQTTnet.AspNetCore;
 
-public sealed class SocketReceiver
+public sealed class SocketReceiver : IDisposable
 {
     readonly SocketAwaitable _awaitable;
     readonly SocketAsyncEventArgs _eventArgs = new();
@@ -33,4 +32,9 @@ public sealed class SocketReceiver
 
         return _awaitable;
     }
+
+    public void Dispose()
+    {
+        _eventArgs.Dispose();
+    }
 }

Source/MQTTnet.AspnetCore/SocketSender.cs

@@ -2,9 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Buffers;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO.Pipelines;
 using System.Net.Sockets;
@@ -12,7 +10,7 @@ using System.Runtime.InteropServices;
 
 namespace MQTTnet.AspNetCore;
 
-public sealed class SocketSender
+public sealed class SocketSender : IDisposable
 {
     readonly SocketAwaitable _awaitable;
     readonly SocketAsyncEventArgs _eventArgs = new();
@@ -28,6 +26,11 @@ public sealed class SocketSender
         _eventArgs.Completed += (_, e) => ((SocketAwaitable)e.UserToken).Complete(e.BytesTransferred, e.SocketError);
     }
 
+    public void Dispose()
+    {
+        _eventArgs.Dispose();
+    }
+
     public SocketAwaitable SendAsync(in ReadOnlySequence<byte> buffers)
     {
         if (buffers.IsSingleSegment)

Source/MQTTnet.Benchmarks/AssemblyInfo.cs

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

Source/MQTTnet.Benchmarks/AsyncLockBenchmark.cs

@@ -2,9 +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.Threading;
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Internal;
@@ -43,7 +40,7 @@ public class AsyncLockBenchmark : BaseBenchmark
 
         if (globalI != tasksCount)
         {
-            throw new Exception($"Code is broken ({globalI})!");
+            throw new InvalidOperationException($"Code is broken ({globalI})!");
         }
     }
 

Source/MQTTnet.Benchmarks/ChannelAdapterBenchmark.cs

@@ -2,9 +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.IO;
-using System.Threading;
 using BenchmarkDotNet.Attributes;
 using MQTTnet.Adapter;
 using MQTTnet.Diagnostics.Logger;
@@ -15,7 +12,7 @@ using MQTTnet.Tests.Mockups;
 namespace MQTTnet.Benchmarks;
 
 [MemoryDiagnoser]
-public sealed class ChannelAdapterBenchmark : BaseBenchmark
+public sealed class ChannelAdapterBenchmark : BaseBenchmark, IDisposable
 {
     MqttChannelAdapter _channelAdapter;
     int _iterations;
@@ -86,4 +83,10 @@ public sealed class ChannelAdapterBenchmark : BaseBenchmark
 
         return buffer.ToArray();
     }
+
+    public void Dispose()
+    {
+        _channelAdapter?.Dispose();
+        _stream?.Dispose();
+    }
 }

Source/MQTTnet.Benchmarks/MQTTnet.Benchmarks.csproj

@@ -1,20 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
         <OutputType>Exe</OutputType>
         <DebugType>Full</DebugType>
-        <TargetFramework>net8.0</TargetFramework>
         <IsPackable>false</IsPackable>
-        <EnableNETAnalyzers>false</EnableNETAnalyzers>
-        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
-        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902;CS8892</NoWarn>
+        <NoWarn>$(NoWarn);CS8892;CA1707;CA1051;CA1822</NoWarn>
         <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
-        <NuGetAuditMode>all</NuGetAuditMode>
-        <NuGetAudit>true</NuGetAudit>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <AnalysisLevel>latest-Recommended</AnalysisLevel>
     </PropertyGroup>
 
     <ItemGroup>

Source/MQTTnet.Benchmarks/MemoryCopyBenchmark.cs

@@ -1,6 +1,5 @@
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
-using System;
 
 
 namespace MQTTnet.Benchmarks;

Source/MQTTnet.Benchmarks/MessageDeliveryBenchmark.cs

@@ -2,10 +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.Collections.Generic;
-using System.Threading;
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using MQTTnet.Packets;
 using MQTTnet.Server;
@@ -13,7 +9,7 @@ using MQTTnet.Server;
 namespace MQTTnet.Benchmarks;
 
 [MemoryDiagnoser]
-public class MessageDeliveryBenchmark : BaseBenchmark
+public sealed class MessageDeliveryBenchmark : BaseBenchmark, IDisposable
 {
     List<string> _allSubscribedTopics; // Keep track of the subset of topics that are subscribed
     CancellationTokenSource _cancellationTokenSource;
@@ -99,10 +95,16 @@ public class MessageDeliveryBenchmark : BaseBenchmark
 
         if (_messagesReceivedCount < _messagesExpectedCount)
         {
-            throw new Exception($"Messages Received Count mismatch, expected {_messagesExpectedCount}, received {_messagesReceivedCount}");
+            throw new InvalidOperationException($"Messages Received Count mismatch, expected {_messagesExpectedCount}, received {_messagesReceivedCount}");
         }
     }
 
+    public void Dispose()
+    {
+        _cancellationTokenSource?.Dispose();
+        _mqttServer?.Dispose();
+    }
+
     [GlobalSetup]
     public void Setup()
     {
@@ -173,7 +175,7 @@ public class MessageDeliveryBenchmark : BaseBenchmark
         var topicIndexStep = totalNumTopics / (_numSubscribedTopicsPerSubscriber * _numSubscribers);
         if (topicIndexStep * _numSubscribedTopicsPerSubscriber * _numSubscribers != totalNumTopics)
         {
-            throw new Exception(
+            throw new InvalidOperationException(
                 $"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}");
         }
 

Source/MQTTnet.Benchmarks/MqttBufferReaderBenchmark.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.Text;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

Source/MQTTnet.Benchmarks/MqttPacketReaderWriterBenchmark.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 BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Formatter;

Source/MQTTnet.Benchmarks/MqttTcpChannelBenchmark.cs

@@ -4,8 +4,6 @@
 
 using System.Buffers;
 using System.Reflection;
-using System.Threading;
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Channel;
@@ -18,9 +16,9 @@ namespace MQTTnet.Benchmarks;
 
 [SimpleJob(RuntimeMoniker.Net60)]
 [MemoryDiagnoser]
-public class MqttTcpChannelBenchmark : BaseBenchmark
+public sealed class MqttTcpChannelBenchmark : BaseBenchmark, IDisposable
 {
-    IMqttChannel _clientChannel;
+    MqttTcpChannel _clientChannel;
     MqttServer _mqttServer;
     IMqttChannel _serverChannel;
 
@@ -84,4 +82,11 @@ public class MqttTcpChannelBenchmark : BaseBenchmark
             await _serverChannel.WriteAsync(buffer, true, CancellationToken.None).ConfigureAwait(false);
         }
     }
+
+    public void Dispose()
+    {
+        _clientChannel?.Dispose();
+        _mqttServer?.Dispose();
+        _serverChannel?.Dispose();
+    }
 }

Source/MQTTnet.Benchmarks/Program.cs

@@ -2,9 +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.Collections.Generic;
-using System.Linq;
 using BenchmarkDotNet.Running;
 
 namespace MQTTnet.Benchmarks;
@@ -92,7 +89,7 @@ public static class Program
             return;
         }
 
-        _selectedBenchmarkIndex = _benchmarks.FindIndex(b => b.Name.Equals(arguments[0]));
+        _selectedBenchmarkIndex = _benchmarks.FindIndex(b => b.Name.Equals(arguments[0], StringComparison.Ordinal));
 
         if (_selectedBenchmarkIndex < 0)
         {

Source/MQTTnet.Benchmarks/ReaderExtensionsBenchmark.cs

@@ -4,16 +4,14 @@ using MQTTnet.AspNetCore;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using System.Buffers;
-using System.IO;
 using System.IO.Pipelines;
-using System.Threading.Tasks;
 
 namespace MQTTnet.Benchmarks;
 
 [SimpleJob(RuntimeMoniker.Net60)]
 [RPlotExporter, RankColumn]
 [MemoryDiagnoser]
-public class ReaderExtensionsBenchmark
+public sealed class ReaderExtensionsBenchmark : IDisposable, IAsyncDisposable
 {
     MqttPacketFormatterAdapter _mqttPacketFormatter;
     MemoryStream _stream;
@@ -83,4 +81,17 @@ public class ReaderExtensionsBenchmark
             }
         }
     }
+
+    public void Dispose()
+    {
+        _stream?.Dispose();
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (_stream != null)
+        {
+            await _stream.DisposeAsync();
+        }
+    }
 }

Source/MQTTnet.Benchmarks/RoundtripProcessingBenchmark.cs

@@ -1,7 +1,6 @@
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Tests.Mockups;
-using MQTTnet.Tests.Server;
 
 namespace MQTTnet.Benchmarks;
 

Source/MQTTnet.Benchmarks/SendPacketAsyncBenchmark.cs

@@ -1,39 +1,19 @@
+using System.Buffers;
+using System.IO.Pipelines;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Formatter;
-using System;
-using System.Buffers;
-using System.IO;
-using System.IO.Pipelines;
-using System.Threading.Tasks;
 
 namespace MQTTnet.Benchmarks;
 
 [SimpleJob(RuntimeMoniker.Net60)]
-[RPlotExporter, RankColumn]
+[RPlotExporter]
+[RankColumn]
 [MemoryDiagnoser]
-public class SendPacketAsyncBenchmark : BaseBenchmark
+public sealed class SendPacketAsyncBenchmark : BaseBenchmark, IDisposable, IAsyncDisposable
 {
-    MemoryStream _stream;
     MqttPacketBuffer _buffer;
-
-    [GlobalSetup]
-    public void GlobalSetup()
-    {
-        _stream = new MemoryStream(1024);
-        var packet = new ArraySegment<byte>(new byte[10]);
-        _buffer = new MqttPacketBuffer(packet);
-    }
-
-    [Benchmark(Baseline = true)]
-    public async ValueTask Before()
-    {
-        _stream.Position = 0;
-        var output = PipeWriter.Create(_stream);
-
-        WritePacketBuffer(output, _buffer);
-        await output.FlushAsync();
-    }
+    MemoryStream _stream;
 
     [Benchmark]
     public async ValueTask After()
@@ -52,6 +32,37 @@ public class SendPacketAsyncBenchmark : BaseBenchmark
         }
     }
 
+    [Benchmark(Baseline = true)]
+    public async ValueTask Before()
+    {
+        _stream.Position = 0;
+        var output = PipeWriter.Create(_stream);
+
+        WritePacketBuffer(output, _buffer);
+        await output.FlushAsync();
+    }
+
+    public void Dispose()
+    {
+        _stream?.Dispose();
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (_stream != null)
+        {
+            await _stream.DisposeAsync();
+        }
+    }
+
+    [GlobalSetup]
+    public void GlobalSetup()
+    {
+        _stream = new MemoryStream(1024);
+        var packet = new ArraySegment<byte>(new byte[10]);
+        _buffer = new MqttPacketBuffer(packet);
+    }
+
     static void WritePacketBuffer(PipeWriter output, MqttPacketBuffer buffer)
     {
         // copy MqttPacketBuffer's Packet and Payload to the same buffer block of PipeWriter

Source/MQTTnet.Benchmarks/SerializerBenchmark.cs

@@ -4,10 +4,7 @@
 
 using BenchmarkDotNet.Attributes;
 using MQTTnet.Packets;
-using System;
 using System.Security.Cryptography.X509Certificates;
-using System.Threading;
-using System.Threading.Tasks;
 using MQTTnet.Adapter;
 using MQTTnet.Channel;
 using MQTTnet.Formatter;
@@ -26,7 +23,7 @@ public class SerializerBenchmark : BaseBenchmark
 {
     MqttPacket _packet;
     ArraySegment<byte> _serializedPacket;
-    IMqttPacketFormatter _serializer;
+    MqttV3PacketFormatter _serializer;
     MqttBufferWriter _bufferWriter;
 
     [GlobalSetup]
@@ -43,7 +40,7 @@ public class SerializerBenchmark : BaseBenchmark
     }
 
     [Benchmark]
-    public void Serialize_10000_Messages()
+    public void Serialize10000Messages()
     {
         for (var i = 0; i < 10000; i++)
         {
@@ -53,7 +50,7 @@ public class SerializerBenchmark : BaseBenchmark
     }
 
     [Benchmark]
-    public void Deserialize_10000_Messages()
+    public void Deserialize10000Messages()
     {
         var channel = new BenchmarkMqttChannel(_serializedPacket);
         var reader = new MqttChannelAdapter(channel, new MqttPacketFormatterAdapter(new MqttBufferWriter(4096, 65535)), new MqttNetEventLogger());
@@ -66,7 +63,7 @@ public class SerializerBenchmark : BaseBenchmark
         }
     }
 
-    class BenchmarkMqttChannel : IMqttChannel
+    sealed class BenchmarkMqttChannel : IMqttChannel
     {
         readonly ArraySegment<byte> _buffer;
         int _position;
@@ -79,7 +76,9 @@ public class SerializerBenchmark : BaseBenchmark
 
         public EndPoint RemoteEndPoint { get; set; }
 
-        public bool IsSecureConnection { get; } = false;
+        public EndPoint LocalEndPoint { get; set; }
+
+        public bool IsSecureConnection { get; }
 
         public X509Certificate2 ClientCertificate { get; set; }
 

Source/MQTTnet.Benchmarks/ServerProcessingBenchmark.cs

@@ -5,7 +5,6 @@
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.Tests.Mockups;
-using MQTTnet.Tests.Server;
 
 namespace MQTTnet.Benchmarks;
 

Source/MQTTnet.Benchmarks/SubscribeBenchmark.cs

@@ -2,8 +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.Collections.Generic;
-using System.Linq;
 using BenchmarkDotNet.Attributes;
 using MQTTnet.Server;
 

Source/MQTTnet.Benchmarks/TcpPipesBenchmark.cs

@@ -5,8 +5,6 @@
 using System.IO.Pipelines;
 using System.Net;
 using System.Net.Sockets;
-using System.Threading;
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using MQTTnet.AspNetCore;

Source/MQTTnet.Benchmarks/TopicGenerator.cs

@@ -1,6 +1,3 @@
-using System;
-using System.Collections.Generic;
-
 namespace MQTTnet.Benchmarks;
 
 public class TopicGenerator

Source/MQTTnet.Benchmarks/UnsubscribeBenchmark.cs

@@ -2,8 +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.Collections.Generic;
-using System.Linq;
 using BenchmarkDotNet.Attributes;
 using MQTTnet.Server;
 

Source/MQTTnet.Extensions.Rpc/DefaultMqttRpcClientTopicGenerationStrategy.cs

@@ -2,8 +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;
-
 namespace MQTTnet.Extensions.Rpc;
 
 public sealed class DefaultMqttRpcClientTopicGenerationStrategy : IMqttRpcClientTopicGenerationStrategy
@@ -12,7 +10,7 @@ public sealed class DefaultMqttRpcClientTopicGenerationStrategy : IMqttRpcClient
     {
         ArgumentNullException.ThrowIfNull(context);
 
-        if (context.MethodName.Contains("/") || context.MethodName.Contains("+") || context.MethodName.Contains("#"))
+        if (context.MethodName.Contains('/') || context.MethodName.Contains('+') || context.MethodName.Contains('#'))
         {
             throw new ArgumentException("The method name cannot contain /, + or #.");
         }

Source/MQTTnet.Extensions.Rpc/IMqttRpcClient.cs

@@ -2,22 +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 System.Threading;
-using System.Threading.Tasks;
 using MQTTnet.Protocol;
 
 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(TimeSpan timeout, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string,object> parameters = null);
 
-    Task<byte[]> ExecuteAsync(
-        string methodName,
-        byte[] payload,
-        MqttQualityOfServiceLevel qualityOfServiceLevel,
-        IDictionary<string, object>? parameters = null,
-        CancellationToken cancellationToken = default);
+    Task<byte[]> ExecuteAsync(string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null, CancellationToken cancellationToken = default);
 }

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

@@ -1,55 +1,19 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
         <AssemblyName>MQTTnet.Extensions.Rpc</AssemblyName>
         <RootNamespace>MQTTnet.Extensions.Rpc</RootNamespace>
-        <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
-        <Company>The contributors of MQTTnet</Company>
-        <Product>MQTTnet</Product>
-        <Description>This is an extension library which allows executing synchronous device calls including a response using MQTTnet.</Description>
-        <Authors>The contributors of MQTTnet</Authors>
-        <PackageId>MQTTnet.Extensions.Rpc</PackageId>
-        <SignAssembly>false</SignAssembly>
-        <DelaySign>false</DelaySign>
-        <PublishRepositoryUrl>true</PublishRepositoryUrl>
-        <IncludeSymbols>true</IncludeSymbols>
-        <SymbolPackageFormat>snupkg</SymbolPackageFormat>
-        <Copyright>Copyright (c) .NET Foundation and Contributors</Copyright>
-        <PackageProjectUrl>https://github.com/dotnet/MQTTnet</PackageProjectUrl>
-        <RepositoryUrl>https://github.com/dotnet/MQTTnet.git</RepositoryUrl>
-        <RepositoryType>git</RepositoryType>
-        <PackageTags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin Blazor</PackageTags>
-        <NeutralLanguage>en-US</NeutralLanguage>
-        <EnableNETAnalyzers>false</EnableNETAnalyzers>
-        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <PackageIcon>nuget.png</PackageIcon>
-        <EmbedUntrackedSources>true</EmbedUntrackedSources>
-        <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <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>
-        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902</NoWarn>
-        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-        <NuGetAuditMode>all</NuGetAuditMode>
-        <NuGetAudit>true</NuGetAudit>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <AnalysisLevel>latest-Recommended</AnalysisLevel>
         <IsAotCompatible>true</IsAotCompatible>
-        <LangVersion>default</LangVersion>
-        <Nullable>enable</Nullable>
+
+        <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
+        <Description>This is an extension library which allows executing synchronous device calls including a response using MQTTnet.</Description>
+        <PackageId>MQTTnet.Extensions.Rpc</PackageId>
+        <PackageTags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin Blazor</PackageTags>
+        <EmbedUntrackedSources>true</EmbedUntrackedSources>
+        <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
+        <GenerateDocumentationFile>true</GenerateDocumentationFile>
     </PropertyGroup>
 
-    <ItemGroup>
-        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
-    </ItemGroup>
-
-    <ItemGroup>
-        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All"/>
-    </ItemGroup>
-
     <ItemGroup>
         <ProjectReference Include="..\MQTTnet\MQTTnet.csproj"/>
     </ItemGroup>

Source/MQTTnet.Extensions.Rpc/MqttFactoryExtensions.cs

@@ -2,8 +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;
-
 namespace MQTTnet.Extensions.Rpc;
 
 public static class MqttFactoryExtensions

Source/MQTTnet.Extensions.Rpc/MqttRpcClient.cs

@@ -2,12 +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.
 
-using System;
 using System.Buffers;
 using System.Collections.Concurrent;
-using System.Collections.Generic;
-using System.Threading;
-using System.Threading.Tasks;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
 using MQTTnet.Internal;
@@ -20,7 +16,7 @@ public sealed class MqttRpcClient : IMqttRpcClient
     readonly IMqttClient _mqttClient;
     readonly MqttRpcClientOptions _options;
 
-    readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new();
+    readonly ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>> _waitingCalls = new ConcurrentDictionary<string, AsyncTaskCompletionSource<byte[]>>();
 
     public MqttRpcClient(IMqttClient mqttClient, MqttRpcClientOptions options)
     {
@@ -42,12 +38,7 @@ public sealed class MqttRpcClient : IMqttRpcClient
         _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, string methodName, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, IDictionary<string, object> parameters = null)
     {
         using var timeoutToken = new CancellationTokenSource(timeout);
         try
@@ -65,12 +56,7 @@ public sealed class MqttRpcClient : IMqttRpcClient
         }
     }
 
-    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)
     {
         ArgumentNullException.ThrowIfNull(methodName);
 
@@ -92,7 +78,7 @@ public sealed class MqttRpcClient : IMqttRpcClient
 
         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);
         }
@@ -113,10 +99,11 @@ public sealed class MqttRpcClient : IMqttRpcClient
             await _mqttClient.SubscribeAsync(subscribeOptions, cancellationToken).ConfigureAwait(false);
             await _mqttClient.PublishAsync(requestMessage, cancellationToken).ConfigureAwait(false);
 
-            using (cancellationToken.Register(() =>
-                   {
-                       awaitable.TrySetCanceled();
-                   }))
+            using (cancellationToken.Register(
+                       () =>
+                       {
+                           awaitable.TrySetCanceled();
+                       }))
             {
                 return await awaitable.Task.ConfigureAwait(false);
             }

Source/MQTTnet.Extensions.Rpc/MqttRpcClientExtensions.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 System.Collections.Generic;
 using System.Text;
-using System.Threading.Tasks;
 using MQTTnet.Protocol;
 
 namespace MQTTnet.Extensions.Rpc;
 
 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));
+        ArgumentNullException.ThrowIfNull(client);
 
         var buffer = Encoding.UTF8.GetBytes(payload ?? string.Empty);
 

Source/MQTTnet.Extensions.Rpc/MqttRpcClientOptionsBuilder.cs

@@ -2,8 +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;
-
 namespace MQTTnet.Extensions.Rpc;
 
 public sealed class MqttRpcClientOptionsBuilder

Source/MQTTnet.Extensions.Rpc/MqttRpcTopicPair.cs

@@ -6,7 +6,7 @@ namespace MQTTnet.Extensions.Rpc;
 
 public sealed class MqttRpcTopicPair
 {
-    public required string RequestTopic { get; init; }
+    public string RequestTopic { get; set; }
 
-    public required string ResponseTopic { get; init; }
+    public string ResponseTopic { get; set; }
 }

Source/MQTTnet.Extensions.Rpc/TopicGenerationContext.cs

@@ -2,20 +2,14 @@
 // 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.Protocol;
 
 namespace MQTTnet.Extensions.Rpc;
 
 public sealed class TopicGenerationContext
 {
-    public TopicGenerationContext(
-        IMqttClient mqttClient,
-        MqttRpcClientOptions options,
-        string methodName,
-        IDictionary<string, object>? parameters,
-        MqttQualityOfServiceLevel qualityOfServiceLevel)
+    public TopicGenerationContext(IMqttClient mqttClient, MqttRpcClientOptions options, string methodName,
+        IDictionary<string, object> parameters, MqttQualityOfServiceLevel qualityOfServiceLevel)
     {
         MethodName = methodName ?? throw new ArgumentNullException(nameof(methodName));
         Parameters = parameters;
@@ -26,12 +20,12 @@ public sealed class TopicGenerationContext
 
     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

Source/MQTTnet.Extensions.Socks5/MQTTnet.Extensions.Socks5.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <AssemblyName>MQTTnet.Extensions.Socks5</AssemblyName>
+        <RootNamespace>MQTTnet.Extensions.Socks5</RootNamespace>
+        <IsAotCompatible>true</IsAotCompatible>
+
+        <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
+        <Description>This is an extension library which adds SOCKS5 proxy support (RFC 1928 / RFC 1929) to the MQTTnet TCP transport.</Description>
+        <PackageId>MQTTnet.Extensions.Socks5</PackageId>
+        <PackageTags>MQTT Message Queue Telemetry Transport MQTTClient SOCKS SOCKS5 Proxy Tunnel Networking IoT InternetOfThings</PackageTags>
+        <EmbedUntrackedSources>true</EmbedUntrackedSources>
+        <PackageReleaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</PackageReleaseNotes>
+        <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\MQTTnet\MQTTnet.csproj"/>
+    </ItemGroup>
+
+</Project>

Source/MQTTnet.Extensions.Socks5/MqttClientOptionsBuilderExtensions.cs

@@ -0,0 +1,39 @@
+// 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.Extensions.Socks5;
+
+/// <summary>
+///     Sugar extensions for configuring a SOCKS5 proxy on the MQTT client options builder.
+/// </summary>
+public static class MqttClientOptionsBuilderExtensions
+{
+    /// <summary>
+    ///     Configures the client to tunnel its TCP connection to the broker through a SOCKS5
+    ///     proxy. A TCP transport (via <c>WithTcpServer(...)</c> or <c>WithEndPoint(...)</c>)
+    ///     must be configured first.
+    /// </summary>
+    public static MqttClientOptionsBuilder WithSocks5Proxy(this MqttClientOptionsBuilder builder, Socks5ProxyOptions options)
+    {
+        ArgumentNullException.ThrowIfNull(builder);
+        ArgumentNullException.ThrowIfNull(options);
+
+        return builder.WithStreamProvider(new Socks5StreamProvider(options));
+    }
+
+    /// <summary>
+    ///     Configures the client to tunnel its TCP connection to the broker through a SOCKS5
+    ///     proxy using the fluent <see cref="Socks5ProxyOptionsBuilder"/>.
+    /// </summary>
+    public static MqttClientOptionsBuilder WithSocks5Proxy(this MqttClientOptionsBuilder builder, Action<Socks5ProxyOptionsBuilder> configure)
+    {
+        ArgumentNullException.ThrowIfNull(builder);
+        ArgumentNullException.ThrowIfNull(configure);
+
+        var optionsBuilder = new Socks5ProxyOptionsBuilder();
+        configure(optionsBuilder);
+
+        return WithSocks5Proxy(builder, optionsBuilder.Build());
+    }
+}

Source/MQTTnet.Extensions.Socks5/Socks5NetworkStream.cs

@@ -0,0 +1,109 @@
+// 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.Net;
+using System.Net.Sockets;
+using MQTTnet.Channel;
+
+namespace MQTTnet.Extensions.Socks5;
+
+/// <summary>
+///     Wraps a <see cref="NetworkStream"/> opened by the SOCKS5 stream provider so
+///     <c>MqttTcpChannel</c> can read the original socket's endpoints via
+///     <see cref="IMqttClientStreamEndPoints"/> while the rest of the I/O delegates to the
+///     underlying stream.
+/// </summary>
+sealed class Socks5NetworkStream : Stream, IMqttClientStreamEndPoints
+{
+    readonly NetworkStream _inner;
+
+    public Socks5NetworkStream(NetworkStream inner, EndPoint localEndPoint, EndPoint remoteEndPoint)
+    {
+        _inner = inner ?? throw new ArgumentNullException(nameof(inner));
+        LocalEndPoint = localEndPoint;
+        RemoteEndPoint = remoteEndPoint;
+    }
+
+    public EndPoint LocalEndPoint { get; }
+
+    public EndPoint RemoteEndPoint { get; }
+
+    public override bool CanRead => _inner.CanRead;
+
+    public override bool CanSeek => _inner.CanSeek;
+
+    public override bool CanWrite => _inner.CanWrite;
+
+    public override bool CanTimeout => _inner.CanTimeout;
+
+    public override long Length => _inner.Length;
+
+    public override long Position
+    {
+        get => _inner.Position;
+        set => _inner.Position = value;
+    }
+
+    public override int ReadTimeout
+    {
+        get => _inner.ReadTimeout;
+        set => _inner.ReadTimeout = value;
+    }
+
+    public override int WriteTimeout
+    {
+        get => _inner.WriteTimeout;
+        set => _inner.WriteTimeout = value;
+    }
+
+    public override void Flush() => _inner.Flush();
+
+    public override Task FlushAsync(CancellationToken cancellationToken) => _inner.FlushAsync(cancellationToken);
+
+    public override int Read(byte[] buffer, int offset, int count) => _inner.Read(buffer, offset, count);
+
+    public override int Read(Span<byte> buffer) => _inner.Read(buffer);
+
+    public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        => _inner.ReadAsync(buffer, offset, count, cancellationToken);
+
+    public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
+        => _inner.ReadAsync(buffer, cancellationToken);
+
+    public override long Seek(long offset, SeekOrigin origin) => _inner.Seek(offset, origin);
+
+    public override void SetLength(long value) => _inner.SetLength(value);
+
+    public override void Write(byte[] buffer, int offset, int count) => _inner.Write(buffer, offset, count);
+
+    public override void Write(ReadOnlySpan<byte> buffer) => _inner.Write(buffer);
+
+    public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        => _inner.WriteAsync(buffer, offset, count, cancellationToken);
+
+    public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default)
+        => _inner.WriteAsync(buffer, cancellationToken);
+
+    public override void Close()
+    {
+        _inner.Close();
+        base.Close();
+    }
+
+    protected override void Dispose(bool disposing)
+    {
+        if (disposing)
+        {
+            _inner.Dispose();
+        }
+
+        base.Dispose(disposing);
+    }
+
+    public override async ValueTask DisposeAsync()
+    {
+        await _inner.DisposeAsync().ConfigureAwait(false);
+        await base.DisposeAsync().ConfigureAwait(false);
+    }
+}

Source/MQTTnet.Extensions.Socks5/Socks5Protocol.cs

@@ -0,0 +1,39 @@
+// 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.Extensions.Socks5;
+
+/// <summary>
+///     Protocol constants for SOCKS5 (RFC 1928) and the username/password sub-negotiation
+///     (RFC 1929). Internal use only.
+/// </summary>
+internal static class Socks5Protocol
+{
+    public const byte Version = 0x05;
+    public const byte AuthSubNegotiationVersion = 0x01;
+
+    public const byte MethodNoAuth = 0x00;
+    public const byte MethodGssApi = 0x01;
+    public const byte MethodUsernamePassword = 0x02;
+    public const byte MethodNoneAcceptable = 0xFF;
+
+    public const byte CommandConnect = 0x01;
+    public const byte Reserved = 0x00;
+
+    public const byte AddressTypeIPv4 = 0x01;
+    public const byte AddressTypeDomainName = 0x03;
+    public const byte AddressTypeIPv6 = 0x04;
+
+    public const byte ReplySucceeded = 0x00;
+    public const byte ReplyGeneralFailure = 0x01;
+    public const byte ReplyConnectionNotAllowed = 0x02;
+    public const byte ReplyNetworkUnreachable = 0x03;
+    public const byte ReplyHostUnreachable = 0x04;
+    public const byte ReplyConnectionRefused = 0x05;
+    public const byte ReplyTtlExpired = 0x06;
+    public const byte ReplyCommandNotSupported = 0x07;
+    public const byte ReplyAddressTypeNotSupported = 0x08;
+
+    public const int MaxStringLength = 255;
+}

Source/MQTTnet.Extensions.Socks5/Socks5ProxyOptions.cs

@@ -0,0 +1,65 @@
+// 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.Net.Sockets;
+
+namespace MQTTnet.Extensions.Socks5;
+
+/// <summary>
+///     Options for the SOCKS5 stream provider (RFC 1928 / RFC 1929).
+///     A new provider can be constructed from these options via
+///     <see cref="MqttClientOptionsBuilderExtensions.WithSocks5Proxy(MqttClientOptionsBuilder, Socks5ProxyOptions)"/>.
+/// </summary>
+public sealed class Socks5ProxyOptions
+{
+    /// <summary>
+    ///     The SOCKS5 proxy host name or IP literal. Must be set.
+    /// </summary>
+    public string Host { get; set; }
+
+    /// <summary>
+    ///     The SOCKS5 proxy port. Defaults to 1080.
+    /// </summary>
+    public int Port { get; set; } = 1080;
+
+    /// <summary>
+    ///     The user name used for the username/password authentication sub-negotiation (RFC 1929).
+    ///     When <c>null</c> or empty, the client will only offer the "no authentication" method.
+    /// </summary>
+    public string Username { get; set; }
+
+    /// <summary>
+    ///     The password (raw bytes per RFC 1929) used for the username/password authentication
+    ///     sub-negotiation. Must be 1..255 bytes when <see cref="Username"/> is set.
+    /// </summary>
+    public byte[] Password { get; set; }
+
+    /// <summary>
+    ///     When <c>true</c> (the default) the broker hostname is forwarded to the proxy as a
+    ///     SOCKS5 <c>DOMAINNAME</c> address type, so DNS resolution happens at the proxy
+    ///     (typical when the broker is behind the proxy in a private network).
+    ///     When <c>false</c>, the hostname is resolved locally before sending the CONNECT request
+    ///     and an IPv4 / IPv6 address type is used.
+    /// </summary>
+    public bool ResolveDnsRemotely { get; set; } = true;
+
+    /// <summary>
+    ///     The maximum time allowed for the full SOCKS5 handshake (TCP connect to proxy + greeting
+    ///     + optional auth + CONNECT). The handshake will be cancelled and a
+    ///     <see cref="MQTTnet.Exceptions.MqttProxyException"/> will be thrown when this elapses.
+    ///     Defaults to 30 seconds.
+    /// </summary>
+    public TimeSpan HandshakeTimeout { get; set; } = TimeSpan.FromSeconds(30);
+
+    /// <summary>
+    ///     Address family preference for the socket connecting to the proxy and for local DNS
+    ///     resolution when <see cref="ResolveDnsRemotely"/> is <c>false</c>.
+    /// </summary>
+    public AddressFamily AddressFamily { get; set; } = AddressFamily.Unspecified;
+
+    public override string ToString()
+    {
+        return $"{Host}:{Port}";
+    }
+}

Source/MQTTnet.Extensions.Socks5/Socks5ProxyOptionsBuilder.cs

@@ -0,0 +1,94 @@
+// 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.Net.Sockets;
+using System.Text;
+
+namespace MQTTnet.Extensions.Socks5;
+
+/// <summary>
+///     Fluent builder for <see cref="Socks5ProxyOptions"/>.
+/// </summary>
+public sealed class Socks5ProxyOptionsBuilder
+{
+    readonly Socks5ProxyOptions _options = new();
+
+    public Socks5ProxyOptions Build()
+    {
+        if (string.IsNullOrEmpty(_options.Host))
+        {
+            throw new InvalidOperationException("A SOCKS5 proxy host must be configured via WithHost.");
+        }
+
+        if (_options.Port <= 0 || _options.Port > 65535)
+        {
+            throw new InvalidOperationException("The SOCKS5 proxy port must be in the range 1..65535.");
+        }
+
+        if (_options.HandshakeTimeout <= TimeSpan.Zero)
+        {
+            throw new InvalidOperationException("The SOCKS5 handshake timeout must be greater than zero.");
+        }
+
+        if (string.IsNullOrEmpty(_options.Username) && _options.Password is { Length: > 0 })
+        {
+            throw new InvalidOperationException("A SOCKS5 password cannot be configured without a username.");
+        }
+
+        if (!string.IsNullOrEmpty(_options.Username) && (_options.Password == null || _options.Password.Length == 0))
+        {
+            throw new InvalidOperationException("A SOCKS5 password must be configured when a username is set.");
+        }
+
+        return _options;
+    }
+
+    public Socks5ProxyOptionsBuilder WithHost(string host)
+    {
+        _options.Host = host ?? throw new ArgumentNullException(nameof(host));
+        return this;
+    }
+
+    public Socks5ProxyOptionsBuilder WithPort(int port)
+    {
+        _options.Port = port;
+        return this;
+    }
+
+    public Socks5ProxyOptionsBuilder WithCredentials(string username, string password)
+    {
+        _options.Username = username;
+        _options.Password = password != null ? Encoding.UTF8.GetBytes(password) : null;
+        return this;
+    }
+
+    public Socks5ProxyOptionsBuilder WithCredentials(string username, byte[] password)
+    {
+        _options.Username = username;
+        _options.Password = password;
+        return this;
+    }
+
+    /// <summary>
+    ///     Controls whether the broker hostname is forwarded to the proxy (remote DNS, default) or
+    ///     resolved locally before issuing the CONNECT request.
+    /// </summary>
+    public Socks5ProxyOptionsBuilder WithResolveDnsRemotely(bool resolveDnsRemotely = true)
+    {
+        _options.ResolveDnsRemotely = resolveDnsRemotely;
+        return this;
+    }
+
+    public Socks5ProxyOptionsBuilder WithHandshakeTimeout(TimeSpan timeout)
+    {
+        _options.HandshakeTimeout = timeout;
+        return this;
+    }
+
+    public Socks5ProxyOptionsBuilder WithAddressFamily(AddressFamily addressFamily)
+    {
+        _options.AddressFamily = addressFamily;
+        return this;
+    }
+}

Source/MQTTnet.Extensions.Socks5/Socks5StreamProvider.cs

@@ -0,0 +1,507 @@
+// 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.Buffers.Binary;
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using MQTTnet.Channel;
+using MQTTnet.Exceptions;
+
+namespace MQTTnet.Extensions.Socks5;
+
+/// <summary>
+///     <see cref="IMqttClientStreamProvider"/> implementation that tunnels the connection through
+///     a SOCKS5 proxy (RFC 1928) with optional username/password authentication (RFC 1929).
+/// </summary>
+public sealed class Socks5StreamProvider : IMqttClientStreamProvider
+{
+    readonly Socks5ProxyOptions _options;
+
+    public Socks5StreamProvider(Socks5ProxyOptions options)
+    {
+        _options = options ?? throw new ArgumentNullException(nameof(options));
+
+        if (string.IsNullOrEmpty(_options.Host))
+        {
+            throw new ArgumentException("Socks5ProxyOptions.Host must be set.", nameof(options));
+        }
+
+        if (_options.Port <= 0 || _options.Port > 65535)
+        {
+            throw new ArgumentOutOfRangeException(nameof(options), _options.Port, "Socks5ProxyOptions.Port must be in the range 1..65535.");
+        }
+
+        if (_options.HandshakeTimeout <= TimeSpan.Zero)
+        {
+            throw new ArgumentOutOfRangeException(nameof(options), _options.HandshakeTimeout, "Socks5ProxyOptions.HandshakeTimeout must be greater than zero.");
+        }
+
+        if (string.IsNullOrEmpty(_options.Username) && _options.Password is { Length: > 0 })
+        {
+            throw new ArgumentException("Socks5ProxyOptions.Password cannot be set without Socks5ProxyOptions.Username.", nameof(options));
+        }
+
+        if (!string.IsNullOrEmpty(_options.Username) && (_options.Password == null || _options.Password.Length == 0))
+        {
+            throw new ArgumentException("Socks5ProxyOptions.Password must be set when Socks5ProxyOptions.Username is set.", nameof(options));
+        }
+    }
+
+    public async Task<Stream> ConnectAsync(EndPoint brokerEndPoint, CancellationToken cancellationToken)
+    {
+        ArgumentNullException.ThrowIfNull(brokerEndPoint);
+
+        using var timeoutCts = new CancellationTokenSource(_options.HandshakeTimeout);
+        using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, timeoutCts.Token);
+        var handshakeToken = linkedCts.Token;
+
+        var addressFamily = _options.AddressFamily;
+        Socket socket = addressFamily == AddressFamily.Unspecified
+            ? new Socket(SocketType.Stream, ProtocolType.Tcp)
+            : new Socket(addressFamily, SocketType.Stream, ProtocolType.Tcp);
+
+        NetworkStream networkStream = null;
+        try
+        {
+            try
+            {
+                await socket.ConnectAsync(_options.Host, _options.Port, handshakeToken).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException) when (timeoutCts.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
+            {
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyUnreachable,
+                    $"Timed out connecting to SOCKS5 proxy after {_options.HandshakeTimeout}.",
+                    _options.ToString());
+            }
+            catch (Exception ex) when (ex is SocketException or IOException)
+            {
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyUnreachable,
+                    $"Could not connect to SOCKS5 proxy: {ex.Message}",
+                    _options.ToString(),
+                    ex);
+            }
+
+            networkStream = new NetworkStream(socket, ownsSocket: true);
+
+            try
+            {
+                await PerformGreetingAndAuthAsync(networkStream, handshakeToken).ConfigureAwait(false);
+                await PerformConnectAsync(networkStream, brokerEndPoint, handshakeToken).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException) when (timeoutCts.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
+            {
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyProtocolError,
+                    $"Timed out during SOCKS5 handshake after {_options.HandshakeTimeout}.",
+                    _options.ToString());
+            }
+            catch (EndOfStreamException ex)
+            {
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyProtocolError,
+                    "The SOCKS5 proxy closed the connection during the handshake.",
+                    _options.ToString(),
+                    ex);
+            }
+            catch (Exception ex) when (ex is IOException or SocketException)
+            {
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyProtocolError,
+                    $"I/O error during SOCKS5 handshake: {ex.Message}",
+                    _options.ToString(),
+                    ex);
+            }
+
+            // Hand off the stream — ownership transfers to the caller.
+            var result = new Socks5NetworkStream(networkStream, socket.LocalEndPoint, socket.RemoteEndPoint);
+            networkStream = null;
+            socket = null;
+            return result;
+        }
+        finally
+        {
+            networkStream?.Dispose();
+            socket?.Dispose();
+        }
+    }
+
+    async Task PerformGreetingAndAuthAsync(NetworkStream stream, CancellationToken cancellationToken)
+    {
+        var hasCredentials = !string.IsNullOrEmpty(_options.Username);
+
+        // VER NMETHODS METHOD[1..n]
+        // We always offer no-auth; we additionally offer user/pass when credentials are configured.
+        byte[] greeting;
+        if (hasCredentials)
+        {
+            greeting = [Socks5Protocol.Version, 0x02, Socks5Protocol.MethodNoAuth, Socks5Protocol.MethodUsernamePassword];
+        }
+        else
+        {
+            greeting = [Socks5Protocol.Version, 0x01, Socks5Protocol.MethodNoAuth];
+        }
+
+        await stream.WriteAsync(greeting, cancellationToken).ConfigureAwait(false);
+
+        // VER METHOD
+        var greetingResponse = new byte[2];
+        await ReadExactlyAsync(stream, greetingResponse, cancellationToken).ConfigureAwait(false);
+
+        if (greetingResponse[0] != Socks5Protocol.Version)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyProtocolError,
+                $"Unexpected SOCKS version in greeting response: 0x{greetingResponse[0]:X2}.",
+                _options.ToString());
+        }
+
+        var chosenMethod = greetingResponse[1];
+        switch (chosenMethod)
+        {
+            case Socks5Protocol.MethodNoAuth:
+                if (hasCredentials)
+                {
+                    // Server accepted no-auth even though we offered credentials: fine, continue.
+                }
+
+                return;
+
+            case Socks5Protocol.MethodUsernamePassword:
+                if (!hasCredentials)
+                {
+                    throw new MqttProxyException(
+                        MqttProxyErrorCode.ProxyProtocolError,
+                        "The SOCKS5 server selected username/password authentication but no credentials are configured.",
+                        _options.ToString());
+                }
+
+                await PerformUsernamePasswordAuthAsync(stream, cancellationToken).ConfigureAwait(false);
+                return;
+
+            case Socks5Protocol.MethodNoneAcceptable:
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyAuthMethodRejected,
+                    "The SOCKS5 server rejected all offered authentication methods.",
+                    _options.ToString());
+
+            default:
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyProtocolError,
+                    $"The SOCKS5 server selected an unsupported authentication method: 0x{chosenMethod:X2}.",
+                    _options.ToString());
+        }
+    }
+
+    async Task PerformUsernamePasswordAuthAsync(NetworkStream stream, CancellationToken cancellationToken)
+    {
+        var usernameBytes = Encoding.UTF8.GetBytes(_options.Username ?? string.Empty);
+        var passwordBytes = _options.Password ?? [];
+
+        if (usernameBytes.Length > Socks5Protocol.MaxStringLength)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyAuthFailed,
+                $"Username exceeds {Socks5Protocol.MaxStringLength} bytes (RFC 1929).",
+                _options.ToString());
+        }
+
+        if (usernameBytes.Length == 0)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyAuthFailed,
+                "Username must be 1..255 bytes (RFC 1929).",
+                _options.ToString());
+        }
+
+        if (passwordBytes.Length > Socks5Protocol.MaxStringLength)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyAuthFailed,
+                $"Password exceeds {Socks5Protocol.MaxStringLength} bytes (RFC 1929).",
+                _options.ToString());
+        }
+
+        if (passwordBytes.Length == 0)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyAuthFailed,
+                "Password must be 1..255 bytes (RFC 1929).",
+                _options.ToString());
+        }
+
+        var request = new byte[3 + usernameBytes.Length + passwordBytes.Length];
+        var offset = 0;
+        request[offset++] = Socks5Protocol.AuthSubNegotiationVersion;
+        request[offset++] = (byte)usernameBytes.Length;
+        Buffer.BlockCopy(usernameBytes, 0, request, offset, usernameBytes.Length);
+        offset += usernameBytes.Length;
+        request[offset++] = (byte)passwordBytes.Length;
+        Buffer.BlockCopy(passwordBytes, 0, request, offset, passwordBytes.Length);
+
+        await stream.WriteAsync(request, cancellationToken).ConfigureAwait(false);
+
+        var response = new byte[2];
+        await ReadExactlyAsync(stream, response, cancellationToken).ConfigureAwait(false);
+
+        if (response[0] != Socks5Protocol.AuthSubNegotiationVersion)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyProtocolError,
+                $"Unexpected SOCKS5 auth sub-negotiation version: 0x{response[0]:X2}.",
+                _options.ToString());
+        }
+
+        if (response[1] != 0x00)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyAuthFailed,
+                $"The SOCKS5 server rejected the supplied credentials (status 0x{response[1]:X2}).",
+                _options.ToString());
+        }
+    }
+
+    async Task PerformConnectAsync(NetworkStream stream, EndPoint brokerEndPoint, CancellationToken cancellationToken)
+    {
+        var request = BuildConnectRequest(brokerEndPoint, out var targetDescription);
+
+        await stream.WriteAsync(request, cancellationToken).ConfigureAwait(false);
+
+        // Reply: VER REP RSV ATYP BND.ADDR BND.PORT
+        var header = new byte[4];
+        await ReadExactlyAsync(stream, header, cancellationToken).ConfigureAwait(false);
+
+        if (header[0] != Socks5Protocol.Version)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyProtocolError,
+                $"Unexpected SOCKS version in CONNECT response: 0x{header[0]:X2}.",
+                _options.ToString());
+        }
+
+        if (header[2] != Socks5Protocol.Reserved)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyProtocolError,
+                $"Unexpected SOCKS5 reserved byte in CONNECT response: 0x{header[2]:X2}.",
+                _options.ToString());
+        }
+
+        var rep = header[1];
+        if (rep != Socks5Protocol.ReplySucceeded)
+        {
+            var (code, description) = MapReplyCode(rep);
+            throw new MqttProxyException(
+                code,
+                $"SOCKS5 CONNECT to '{targetDescription}' failed: {description}.",
+                _options.ToString());
+        }
+
+        // Discard BND.ADDR / BND.PORT. The length depends on ATYP and we tolerate unexpected lengths.
+        var atyp = header[3];
+        switch (atyp)
+        {
+            case Socks5Protocol.AddressTypeIPv4:
+                await SkipAsync(stream, 4 + 2, cancellationToken).ConfigureAwait(false);
+                break;
+
+            case Socks5Protocol.AddressTypeIPv6:
+                await SkipAsync(stream, 16 + 2, cancellationToken).ConfigureAwait(false);
+                break;
+
+            case Socks5Protocol.AddressTypeDomainName:
+                var lenBuf = new byte[1];
+                await ReadExactlyAsync(stream, lenBuf, cancellationToken).ConfigureAwait(false);
+                await SkipAsync(stream, lenBuf[0] + 2, cancellationToken).ConfigureAwait(false);
+                break;
+
+            default:
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyProtocolError,
+                    $"Unexpected SOCKS5 address type in CONNECT response: 0x{atyp:X2}.",
+                    _options.ToString());
+        }
+    }
+
+    byte[] BuildConnectRequest(EndPoint brokerEndPoint, out string targetDescription)
+    {
+        // Layout: VER CMD RSV ATYP DST.ADDR DST.PORT
+        if (brokerEndPoint is DnsEndPoint dns)
+        {
+            if (_options.ResolveDnsRemotely)
+            {
+                return BuildDomainConnectRequest(dns.Host, dns.Port, out targetDescription);
+            }
+
+            var addresses = ResolveDns(dns.Host, dns.Port);
+            return BuildIpConnectRequest(addresses, dns.Port, out targetDescription);
+        }
+
+        if (brokerEndPoint is IPEndPoint ip)
+        {
+            return BuildIpConnectRequest([ip.Address], ip.Port, out targetDescription);
+        }
+
+        throw new MqttProxyException(
+            MqttProxyErrorCode.ProxyAddressTypeNotSupported,
+            $"Broker endpoint of type '{brokerEndPoint.GetType().Name}' is not supported by the SOCKS5 stream provider.",
+            _options.ToString());
+    }
+
+    IPAddress[] ResolveDns(string host, int port)
+    {
+        try
+        {
+            var addresses = _options.AddressFamily == AddressFamily.Unspecified
+                ? Dns.GetHostAddresses(host)
+                : Dns.GetHostAddresses(host, _options.AddressFamily);
+
+            if (addresses == null || addresses.Length == 0)
+            {
+                throw new MqttProxyException(
+                    MqttProxyErrorCode.ProxyHostUnreachable,
+                    $"DNS resolution for '{host}:{port}' returned no addresses.",
+                    _options.ToString());
+            }
+
+            return addresses;
+        }
+        catch (SocketException ex)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyHostUnreachable,
+                $"Local DNS resolution failed for '{host}:{port}': {ex.Message}",
+                _options.ToString(),
+                ex);
+        }
+    }
+
+    byte[] BuildIpConnectRequest(IPAddress[] addresses, int port, out string targetDescription)
+    {
+        var preferredFamily = _options.AddressFamily == AddressFamily.Unspecified
+            ? AddressFamily.InterNetwork
+            : _options.AddressFamily;
+
+        IPAddress chosen = null;
+        foreach (var address in addresses)
+        {
+            if (address.AddressFamily == preferredFamily)
+            {
+                chosen = address;
+                break;
+            }
+        }
+
+        chosen ??= addresses[0];
+
+        targetDescription = $"{chosen}:{port}";
+
+        if (chosen.AddressFamily == AddressFamily.InterNetwork)
+        {
+            var addr = chosen.GetAddressBytes();
+            var request = new byte[4 + 4 + 2];
+            request[0] = Socks5Protocol.Version;
+            request[1] = Socks5Protocol.CommandConnect;
+            request[2] = Socks5Protocol.Reserved;
+            request[3] = Socks5Protocol.AddressTypeIPv4;
+            Buffer.BlockCopy(addr, 0, request, 4, 4);
+            BinaryPrimitives.WriteUInt16BigEndian(request.AsSpan(8, 2), (ushort)port);
+            return request;
+        }
+
+        if (chosen.AddressFamily == AddressFamily.InterNetworkV6)
+        {
+            var addr = chosen.GetAddressBytes();
+            var request = new byte[4 + 16 + 2];
+            request[0] = Socks5Protocol.Version;
+            request[1] = Socks5Protocol.CommandConnect;
+            request[2] = Socks5Protocol.Reserved;
+            request[3] = Socks5Protocol.AddressTypeIPv6;
+            Buffer.BlockCopy(addr, 0, request, 4, 16);
+            BinaryPrimitives.WriteUInt16BigEndian(request.AsSpan(20, 2), (ushort)port);
+            return request;
+        }
+
+        throw new MqttProxyException(
+            MqttProxyErrorCode.ProxyAddressTypeNotSupported,
+            $"IP address family '{chosen.AddressFamily}' is not supported by SOCKS5.",
+            _options.ToString());
+    }
+
+    byte[] BuildDomainConnectRequest(string host, int port, out string targetDescription)
+    {
+        var hostBytes = Encoding.UTF8.GetBytes(host ?? string.Empty);
+        if (hostBytes.Length == 0)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyHostUnreachable,
+                "Broker host is empty.",
+                _options.ToString());
+        }
+
+        if (hostBytes.Length > Socks5Protocol.MaxStringLength)
+        {
+            throw new MqttProxyException(
+                MqttProxyErrorCode.ProxyAddressTypeNotSupported,
+                $"Broker host exceeds the SOCKS5 DOMAINNAME limit of {Socks5Protocol.MaxStringLength} bytes.",
+                _options.ToString());
+        }
+
+        targetDescription = $"{host}:{port}";
+
+        var request = new byte[4 + 1 + hostBytes.Length + 2];
+        request[0] = Socks5Protocol.Version;
+        request[1] = Socks5Protocol.CommandConnect;
+        request[2] = Socks5Protocol.Reserved;
+        request[3] = Socks5Protocol.AddressTypeDomainName;
+        request[4] = (byte)hostBytes.Length;
+        Buffer.BlockCopy(hostBytes, 0, request, 5, hostBytes.Length);
+        BinaryPrimitives.WriteUInt16BigEndian(request.AsSpan(5 + hostBytes.Length, 2), (ushort)port);
+        return request;
+    }
+
+    static (MqttProxyErrorCode Code, string Description) MapReplyCode(byte rep)
+    {
+        return rep switch
+        {
+            Socks5Protocol.ReplyGeneralFailure => (MqttProxyErrorCode.ProxyGeneralFailure, "general SOCKS server failure"),
+            Socks5Protocol.ReplyConnectionNotAllowed => (MqttProxyErrorCode.ProxyConnectionNotAllowed, "connection not allowed by ruleset"),
+            Socks5Protocol.ReplyNetworkUnreachable => (MqttProxyErrorCode.ProxyNetworkUnreachable, "network unreachable"),
+            Socks5Protocol.ReplyHostUnreachable => (MqttProxyErrorCode.ProxyHostUnreachable, "host unreachable"),
+            Socks5Protocol.ReplyConnectionRefused => (MqttProxyErrorCode.ProxyConnectionRefused, "connection refused"),
+            Socks5Protocol.ReplyTtlExpired => (MqttProxyErrorCode.ProxyTtlExpired, "TTL expired"),
+            Socks5Protocol.ReplyCommandNotSupported => (MqttProxyErrorCode.ProxyCommandNotSupported, "command not supported"),
+            Socks5Protocol.ReplyAddressTypeNotSupported => (MqttProxyErrorCode.ProxyAddressTypeNotSupported, "address type not supported"),
+            _ => (MqttProxyErrorCode.ProxyUnknownError, $"unknown reply code 0x{rep:X2}")
+        };
+    }
+
+    static async Task ReadExactlyAsync(NetworkStream stream, byte[] buffer, CancellationToken cancellationToken)
+    {
+        var offset = 0;
+        while (offset < buffer.Length)
+        {
+            var read = await stream.ReadAsync(buffer.AsMemory(offset, buffer.Length - offset), cancellationToken).ConfigureAwait(false);
+            if (read <= 0)
+            {
+                throw new EndOfStreamException();
+            }
+
+            offset += read;
+        }
+    }
+
+    static async Task SkipAsync(NetworkStream stream, int count, CancellationToken cancellationToken)
+    {
+        if (count <= 0)
+        {
+            return;
+        }
+
+        var buffer = new byte[count];
+        await ReadExactlyAsync(stream, buffer, cancellationToken).ConfigureAwait(false);
+    }
+}

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

@@ -1,56 +1,24 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
         <AssemblyName>MQTTnet.Extensions.TopicTemplate</AssemblyName>
         <RootNamespace>MQTTnet.Extensions.TopicTemplate</RootNamespace>
+        <IsAotCompatible>true</IsAotCompatible>
+
         <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
-        <Company>The contributors of MQTTnet</Company>
-        <Product>MQTTnet</Product>
         <Description>
            Provides mqtt topic templating logic to support dispatch,
            routing and similar functionality based on the well known moustache syntax (AsyncAPI compatible).
         </Description>
 		<PackageReadmeFile>README.md</PackageReadmeFile>
-        <Authors>The contributors of MQTTnet</Authors>
         <PackageId>MQTTnet.Extensions.TopicTemplate</PackageId>
-        <SignAssembly>false</SignAssembly>
-        <DelaySign>false</DelaySign>
-        <PublishRepositoryUrl>true</PublishRepositoryUrl>
-        <IncludeSymbols>true</IncludeSymbols>
-        <SymbolPackageFormat>snupkg</SymbolPackageFormat>
-        <Copyright>Copyright (c) .NET Foundation and Contributors</Copyright>
-        <PackageProjectUrl>https://github.com/dotnet/MQTTnet</PackageProjectUrl>
-        <RepositoryUrl>https://github.com/dotnet/MQTTnet.git</RepositoryUrl>
-        <RepositoryType>git</RepositoryType>
         <PackageTags>MQTT Message Queue Telemetry MQTTClient Messaging Routing AsyncAPI Template</PackageTags>
-        <NeutralLanguage>en-US</NeutralLanguage>
-        <PackageIcon>nuget.png</PackageIcon>
-        <EmbedUntrackedSources>true</EmbedUntrackedSources>
-        <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <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>
-        <None Include="README.md">
-            <Pack>True</Pack>
-            <PackagePath>\</PackagePath>
-        </None>
-    </ItemGroup>
-
-    <ItemGroup>
-        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
-    </ItemGroup>
-
-    <ItemGroup>
-        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" />
         <PackageReference Include="System.ValueTuple" Version="4.6.1" />
     </ItemGroup>
 

Source/MQTTnet.Extensions.TopicTemplate/MqttTopicTemplate.cs

@@ -2,11 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
-using System.Linq;
 using System.Text.RegularExpressions;
-using System.Threading;
 using MQTTnet.Protocol;
 
 namespace MQTTnet.Extensions.TopicTemplate;
@@ -84,13 +80,13 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
         {
             var filter = TopicFilter;
             // append slash if neccessary
-            if (filter.Length > 0 && !filter.EndsWith(MqttTopicFilterComparer.LevelSeparator.ToString()) && !filter.EndsWith(MqttTopicFilterComparer.MultiLevelWildcard.ToString()))
+            if (filter.Length > 0 && !filter.EndsWith(MqttTopicFilterComparer.LevelSeparator) && !filter.EndsWith(MqttTopicFilterComparer.MultiLevelWildcard))
             {
                 filter += MqttTopicFilterComparer.LevelSeparator;
             }
 
             // append hash if neccessary
-            if (!filter.EndsWith(MqttTopicFilterComparer.MultiLevelWildcard.ToString()))
+            if (!filter.EndsWith(MqttTopicFilterComparer.MultiLevelWildcard))
             {
                 filter += MqttTopicFilterComparer.MultiLevelWildcard;
             }
@@ -161,12 +157,12 @@ public sealed class MqttTopicTemplate : IEquatable<MqttTopicTemplate>
             return new MqttTopicTemplate(MqttTopicFilterComparer.MultiLevelWildcard.ToString());
         }
 
-        if (root.Contains(MqttTopicFilterComparer.LevelSeparator) && !root.EndsWith(MqttTopicFilterComparer.LevelSeparator.ToString()) && !root.EndsWith("}"))
+        if (root.Contains(MqttTopicFilterComparer.LevelSeparator) && !root.EndsWith(MqttTopicFilterComparer.LevelSeparator.ToString(), StringComparison.InvariantCulture) && !root.EndsWith('}'))
         {
             root = root.Substring(0, root.LastIndexOf(MqttTopicFilterComparer.LevelSeparator) + 1);
         }
 
-        if (root.EndsWith(MqttTopicFilterComparer.LevelSeparator.ToString()))
+        if (root.EndsWith(MqttTopicFilterComparer.LevelSeparator.ToString(), StringComparison.InvariantCulture))
         {
             root += MqttTopicFilterComparer.SingleLevelWildcard;
         }

Source/MQTTnet.Extensions.TopicTemplate/TopicTemplateExtensions.cs

@@ -2,8 +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.Linq;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 

Source/MQTTnet.Server/Disconnecting/MqttServerClientDisconnectOptionsBuilder.cs

@@ -40,6 +40,7 @@ public sealed class MqttServerClientDisconnectOptionsBuilder
         return this;
     }
 
+    [Obsolete("Please use more performance `WithUserProperty` with ArraySegment<byte> or ReadOnlyMemory<byte> for the value.")]
     public MqttServerClientDisconnectOptionsBuilder WithUserProperty(string name, string value)
     {
         if (_options.UserProperties == null)
@@ -50,4 +51,26 @@ public sealed class MqttServerClientDisconnectOptionsBuilder
         _options.UserProperties.Add(new MqttUserProperty(name, value));
         return this;
     }
+
+    public MqttServerClientDisconnectOptionsBuilder WithUserProperty(string name, ReadOnlyMemory<byte> value)
+    {
+        if (_options.UserProperties == null)
+        {
+            _options.UserProperties = new List<MqttUserProperty>();
+        }
+
+        _options.UserProperties.Add(new MqttUserProperty(name, value));
+        return this;
+    }
+
+    public MqttServerClientDisconnectOptionsBuilder WithUserProperty(string name, ArraySegment<byte> value)
+    {
+        if (_options.UserProperties == null)
+        {
+            _options.UserProperties = new List<MqttUserProperty>();
+        }
+
+        _options.UserProperties.Add(new MqttUserProperty(name, value));
+        return this;
+    }
 }

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationOptions.cs

@@ -8,9 +8,9 @@ namespace MQTTnet.Server.EnhancedAuthentication;
 
 public sealed class ExchangeEnhancedAuthenticationOptions
 {
-    public byte[]? AuthenticationData { get; set; }
+    public byte[] AuthenticationData { get; set; }
 
-    public string? ReasonString { get; set; }
+    public string ReasonString { get; set; }
 
-    public List<MqttUserProperty>? UserProperties { get; set; }
+    public List<MqttUserProperty> UserProperties { get; set; }
 }

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationOptionsFactory.cs

@@ -51,13 +51,39 @@ public sealed class ExchangeEnhancedAuthenticationOptionsFactory
         return this;
     }
 
+    [Obsolete("Please use more performance `WithUserProperty` with ArraySegment<byte> or ReadOnlyMemory<byte> for the value.")]
     public ExchangeEnhancedAuthenticationOptionsFactory WithUserProperty(string name, string value)
     {
-        if (name == null)
+        ArgumentNullException.ThrowIfNull(name);
+
+        if (_options.UserProperties == null)
         {
-            throw new ArgumentNullException(nameof(name));
+            _options.UserProperties = new List<MqttUserProperty>();
         }
 
+        _options.UserProperties.Add(new MqttUserProperty(name, value));
+
+        return this;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithUserProperty(string name, ReadOnlyMemory<byte> value)
+    {
+        ArgumentNullException.ThrowIfNull(name);
+
+        if (_options.UserProperties == null)
+        {
+            _options.UserProperties = new List<MqttUserProperty>();
+        }
+
+        _options.UserProperties.Add(new MqttUserProperty(name, value));
+
+        return this;
+    }
+
+    public ExchangeEnhancedAuthenticationOptionsFactory WithUserProperty(string name, ArraySegment<byte> value)
+    {
+        ArgumentNullException.ThrowIfNull(name);
+
         if (_options.UserProperties == null)
         {
             _options.UserProperties = new List<MqttUserProperty>();

Source/MQTTnet.Server/EnhancedAuthentication/ExchangeEnhancedAuthenticationResult.cs

@@ -4,9 +4,9 @@ namespace MQTTnet.Server.EnhancedAuthentication;
 
 public sealed class ExchangeEnhancedAuthenticationResult
 {
-    public string? ReasonString { get; init; }
+    public string ReasonString { get; set; }
 
-    public List<MqttUserProperty>? UserProperties { get; init; }
+    public List<MqttUserProperty> UserProperties { get; set; }
 
-    public byte[]? AuthenticationData { get; init; }
+    public byte[] AuthenticationData { get; set; }
 }

Source/MQTTnet.Server/Events/ClientConnectedEventArgs.cs

@@ -22,15 +22,15 @@ public sealed class ClientConnectedEventArgs : EventArgs
         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.
@@ -38,7 +38,7 @@ public sealed class ClientConnectedEventArgs : EventArgs
     public EndPoint RemoteEndPoint { get; }
 
     [Obsolete("Use RemoteEndPoint instead.")]
-    public string? Endpoint => RemoteEndPoint?.ToString();
+    public string Endpoint => RemoteEndPoint?.ToString();
 
     /// <summary>
     ///     Gets the protocol version which is used by the connected client.
@@ -53,16 +53,16 @@ public sealed class ClientConnectedEventArgs : EventArgs
     /// <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());
+    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

@@ -35,24 +35,24 @@ public sealed class ClientDisconnectedEventArgs : EventArgs
     ///     Gets the client identifier.
     ///     Hint: This identifier needs to be unique over all used clients / devices on the broker to avoid connection issues.
     /// </summary>
-    public string ClientId => _connectPacket.ClientId!;
+    public string ClientId => _connectPacket.ClientId;
 
     /// <summary>
     ///     Gets the user name of the client.
     /// </summary>
-    public string? UserName => _connectPacket.Username;
+    public string UserName => _connectPacket.Username;
 
     /// <summary>
     ///     Gets the password of the client.
     /// </summary>
-    public string? Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
+    public string Password => Encoding.UTF8.GetString(_connectPacket.Password.AsSpan());
 
     public MqttClientDisconnectType DisconnectType { get; }
 
     public EndPoint RemoteEndPoint { get; }
 
     [Obsolete("Use RemoteEndPoint instead.")]
-    public string? Endpoint => RemoteEndPoint?.ToString();
+    public string Endpoint => RemoteEndPoint?.ToString();
 
     /// <summary>
     ///     Gets the reason code sent by the client.
@@ -66,7 +66,7 @@ public sealed class ClientDisconnectedEventArgs : EventArgs
     ///     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.
@@ -85,5 +85,5 @@ public sealed class ClientDisconnectedEventArgs : EventArgs
     ///     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/InterceptingPacketEventArgs.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.Server;
 
 public sealed class InterceptingPacketEventArgs : EventArgs
 {
-    public InterceptingPacketEventArgs(CancellationToken cancellationToken, string clientId, string userName, EndPoint remoteEndPoint, MqttPacket packet, IDictionary sessionItems)
+    public InterceptingPacketEventArgs(string clientId, string userName, EndPoint remoteEndPoint, MqttPacket packet, IDictionary sessionItems, CancellationToken cancellationToken)
     {
         CancellationToken = cancellationToken;
         ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));

Source/MQTTnet.Server/Events/InterceptingPublishEventArgs.cs

@@ -8,7 +8,7 @@ namespace MQTTnet.Server;
 
 public sealed class InterceptingPublishEventArgs : EventArgs
 {
-    public InterceptingPublishEventArgs(MqttApplicationMessage applicationMessage, CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems)
+    public InterceptingPublishEventArgs(MqttApplicationMessage applicationMessage, string clientId, string userName, IDictionary sessionItems, CancellationToken cancellationToken)
     {
         ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
         CancellationToken = cancellationToken;
@@ -30,11 +30,6 @@ public sealed class InterceptingPublishEventArgs : EventArgs
     /// </summary>
     public string ClientId { get; }
 
-    /// <summary>
-    /// Gets the user name of the client.
-    /// </summary>
-    public string UserName { get; }
-
     public bool CloseConnection { get; set; }
 
     /// <summary>
@@ -45,10 +40,15 @@ public sealed class InterceptingPublishEventArgs : EventArgs
     /// <summary>
     ///     Gets the response which will be sent to the client via the PUBACK etc. packets.
     /// </summary>
-    public PublishResponse Response { get; } = new PublishResponse();
+    public PublishResponse Response { get; } = new();
 
     /// <summary>
     ///     Gets or sets a key/value collection that can be used to share data within the scope of this session.
     /// </summary>
     public IDictionary SessionItems { get; }
+
+    /// <summary>
+    ///     Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
 }

Source/MQTTnet.Server/Events/InterceptingSubscriptionEventArgs.cs

@@ -10,12 +10,12 @@ namespace MQTTnet.Server;
 public sealed class InterceptingSubscriptionEventArgs : EventArgs
 {
     public InterceptingSubscriptionEventArgs(
-        CancellationToken cancellationToken,
         string clientId,
         string userName,
         MqttSessionStatus session,
         MqttTopicFilter topicFilter,
-        List<MqttUserProperty> userProperties)
+        List<MqttUserProperty> userProperties,
+        CancellationToken cancellationToken)
     {
         CancellationToken = cancellationToken;
         ClientId = clientId;
@@ -36,11 +36,6 @@ public sealed class InterceptingSubscriptionEventArgs : EventArgs
     /// </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>
@@ -61,7 +56,7 @@ public sealed class InterceptingSubscriptionEventArgs : EventArgs
     /// <summary>
     ///     Gets the response which will be sent to the client via the SUBACK packet.
     /// </summary>
-    public SubscribeResponse Response { get; } = new SubscribeResponse();
+    public SubscribeResponse Response { get; } = new();
 
     /// <summary>
     ///     Gets the current client session.
@@ -79,6 +74,11 @@ public sealed class InterceptingSubscriptionEventArgs : EventArgs
     /// </summary>
     public MqttTopicFilter TopicFilter { get; set; }
 
+    /// <summary>
+    ///     Gets the user name of the client.
+    /// </summary>
+    public string UserName { get; }
+
     /// <summary>
     ///     Gets or sets the user properties.
     ///     <remarks>MQTT 5.0.0+ feature.</remarks>

Source/MQTTnet.Server/Events/InterceptingUnsubscriptionEventArgs.cs

@@ -9,7 +9,7 @@ namespace MQTTnet.Server;
 
 public sealed class InterceptingUnsubscriptionEventArgs : EventArgs
 {
-    public InterceptingUnsubscriptionEventArgs(CancellationToken cancellationToken, string clientId, string userName, IDictionary sessionItems, string topic, List<MqttUserProperty> userProperties)
+    public InterceptingUnsubscriptionEventArgs(string clientId, string userName, IDictionary sessionItems, string topic, List<MqttUserProperty> userProperties, CancellationToken cancellationToken)
     {
         CancellationToken = cancellationToken;
         ClientId = clientId;

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

@@ -12,7 +12,7 @@ namespace MQTTnet.Server.Internal.Adapter;
 
 public sealed class MqttTcpServerAdapter : IMqttServerAdapter
 {
-    readonly List<MqttTcpServerListener> _listeners = new();
+    readonly List<MqttTcpServerListener> _listeners = new List<MqttTcpServerListener>();
 
     CancellationTokenSource _cancellationTokenSource;
 

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

@@ -165,8 +165,8 @@ public sealed class MqttTcpServerListener : IDisposable
 
     async Task TryHandleClientConnectionAsync(CrossPlatformSocket clientSocket)
     {
-        Stream? stream = null;
-        EndPoint? remoteEndPoint = null;
+        Stream stream = null;
+        EndPoint remoteEndPoint = null;
 
         try
         {
@@ -202,16 +202,21 @@ public sealed class MqttTcpServerListener : IDisposable
 
                 clientCertificate = sslStream.RemoteCertificate as X509Certificate2;
 
+                // TODO: Check why this export is needed. Is there something else in the RemoteCertificate as a X509Certificate2???
                 if (clientCertificate == null && sslStream.RemoteCertificate != null)
                 {
+                    #if NET10_0_OR_GREATER
+                    clientCertificate = X509CertificateLoader.LoadCertificate(sslStream.RemoteCertificate.Export(X509ContentType.Cert));
+                    #else
                     clientCertificate = new X509Certificate2(sslStream.RemoteCertificate.Export(X509ContentType.Cert));
+                    #endif
                 }
             }
 
             var clientHandler = ClientHandler;
             if (clientHandler != null)
             {
-                var tcpChannel = new MqttTcpChannel(stream, remoteEndPoint, clientCertificate);
+                var tcpChannel = new MqttTcpChannel(stream, _localEndPoint, remoteEndPoint, clientCertificate);
                 var bufferWriter = new MqttBufferWriter(_serverOptions.WriterBufferSize, _serverOptions.WriterBufferSizeMax);
                 var packetFormatterAdapter = new MqttPacketFormatterAdapter(bufferWriter);
 

Source/MQTTnet.Server/Internal/MqttClientSessionsManager.cs

@@ -131,7 +131,7 @@ public sealed class MqttClientSessionsManager : ISubscriptionChangedNotification
         // Allow the user to intercept application message...
         if (_eventContainer.InterceptingPublishEvent.HasHandlers)
         {
-            var interceptingPublishEventArgs = new InterceptingPublishEventArgs(applicationMessage, cancellationToken, senderId, senderUserName, senderSessionItems);
+            var interceptingPublishEventArgs = new InterceptingPublishEventArgs(applicationMessage, senderId, senderUserName, senderSessionItems, cancellationToken);
             if (string.IsNullOrEmpty(interceptingPublishEventArgs.ApplicationMessage.Topic))
             {
                 // This can happen if a topic alias us used but the topic is
@@ -437,7 +437,7 @@ public sealed class MqttClientSessionsManager : ISubscriptionChangedNotification
         }
     }
 
-    public void OnSubscriptionsAdded(MqttSession clientSession, List<string> topics)
+    public void OnSubscriptionsAdded(MqttSession clientSession, List<string> subscriptionsTopics)
     {
         _sessionsManagementLock.EnterWriteLock();
         try
@@ -448,7 +448,7 @@ public sealed class MqttClientSessionsManager : ISubscriptionChangedNotification
                 _subscriberSessions.Add(clientSession);
             }
 
-            foreach (var topic in topics)
+            foreach (var topic in subscriptionsTopics)
             {
                 clientSession.AddSubscribedTopic(topic);
             }
@@ -667,7 +667,7 @@ public sealed class MqttClientSessionsManager : ISubscriptionChangedNotification
         }
     }
 
-    async Task<MqttConnectPacket?> ReceiveConnectPacket(IMqttChannelAdapter channelAdapter, CancellationToken cancellationToken)
+    async Task<MqttConnectPacket> ReceiveConnectPacket(IMqttChannelAdapter channelAdapter, CancellationToken cancellationToken)
     {
         try
         {

Source/MQTTnet.Server/Internal/MqttClientSubscriptionsManager.cs

@@ -81,7 +81,7 @@ public sealed class MqttClientSubscriptionsManager : IDisposable
             return CheckSubscriptionsResult.NotSubscribed;
         }
 
-        var senderIsReceiver = string.Equals(senderId, _session.Id);
+        var senderIsReceiver = string.Equals(senderId, _session.Id, StringComparison.Ordinal);
         var maxQoSLevel = -1; // Not subscribed.
 
         HashSet<uint> subscriptionIdentifiers = null;
@@ -460,7 +460,7 @@ public sealed class MqttClientSubscriptionsManager : IDisposable
         List<MqttUserProperty> userProperties,
         CancellationToken cancellationToken)
     {
-        var eventArgs = new InterceptingSubscriptionEventArgs(cancellationToken, _session.Id, _session.UserName, new MqttSessionStatus(_session), topicFilter, userProperties);
+        var eventArgs = new InterceptingSubscriptionEventArgs(_session.Id, _session.UserName, new MqttSessionStatus(_session), topicFilter, userProperties, cancellationToken);
 
         if (topicFilter.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
         {
@@ -475,7 +475,7 @@ public sealed class MqttClientSubscriptionsManager : IDisposable
             eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.GrantedQoS2;
         }
 
-        if (topicFilter.Topic.StartsWith("$share/"))
+        if (topicFilter.Topic.StartsWith("$share/", StringComparison.InvariantCulture))
         {
             eventArgs.Response.ReasonCode = MqttSubscribeReasonCode.SharedSubscriptionsNotSupported;
         }
@@ -493,7 +493,7 @@ public sealed class MqttClientSubscriptionsManager : IDisposable
         List<MqttUserProperty> userProperties,
         CancellationToken cancellationToken)
     {
-        var clientUnsubscribingTopicEventArgs = new InterceptingUnsubscriptionEventArgs(cancellationToken, _session.Id, _session.UserName, _session.Items, topicFilter, userProperties)
+        var clientUnsubscribingTopicEventArgs = new InterceptingUnsubscriptionEventArgs(_session.Id, _session.UserName, _session.Items, topicFilter, userProperties, cancellationToken)
         {
             Response =
             {

Source/MQTTnet.Server/Internal/MqttConnectedClient.cs

@@ -156,7 +156,7 @@ public sealed class MqttConnectedClient : IDisposable
                 // TODO: Maybe adding a configuration option is requested in the future.
                 if (disconnectOptions != null)
                 {
-                    if (disconnectOptions.ReasonCode != MqttDisconnectReasonCode.NormalDisconnection || disconnectOptions.UserProperties?.Any() == true ||
+                    if (disconnectOptions.ReasonCode != MqttDisconnectReasonCode.NormalDisconnection || disconnectOptions.UserProperties?.Count > 0 ||
                         !string.IsNullOrEmpty(disconnectOptions.ReasonString) || !string.IsNullOrEmpty(disconnectOptions.ServerReference))
                     {
                         // It is very important to send the DISCONNECT packet here BEFORE cancelling the
@@ -218,6 +218,8 @@ public sealed class MqttConnectedClient : IDisposable
         HandleTopicAlias(publishPacket);
 
         var applicationMessage = MqttApplicationMessageFactory.Create(publishPacket);
+        // Topic aliases are scoped to this network connection and must not be forwarded to other clients.
+        applicationMessage.TopicAlias = 0;
 
         var dispatchApplicationMessageResult =
             await _sessionsManager.DispatchApplicationMessage(Id, UserName, Session.Items, applicationMessage, cancellationToken).ConfigureAwait(false);
@@ -349,7 +351,7 @@ public sealed class MqttConnectedClient : IDisposable
             return packet;
         }
 
-        var interceptingPacketEventArgs = new InterceptingPacketEventArgs(cancellationToken, Id, UserName, RemoteEndPoint, packet, Session.Items);
+        var interceptingPacketEventArgs = new InterceptingPacketEventArgs(Id, UserName, RemoteEndPoint, packet, Session.Items, cancellationToken);
         await _eventContainer.InterceptingOutboundPacketEvent.InvokeAsync(interceptingPacketEventArgs).ConfigureAwait(false);
 
         if (!interceptingPacketEventArgs.ProcessPacket || packet == null)
@@ -395,7 +397,7 @@ public sealed class MqttConnectedClient : IDisposable
 
                 if (_eventContainer.InterceptingInboundPacketEvent.HasHandlers)
                 {
-                    var interceptingPacketEventArgs = new InterceptingPacketEventArgs(cancellationToken, Id, UserName, RemoteEndPoint, currentPacket, Session.Items);
+                    var interceptingPacketEventArgs = new InterceptingPacketEventArgs(Id, UserName, RemoteEndPoint, currentPacket, Session.Items, cancellationToken);
                     await _eventContainer.InterceptingInboundPacketEvent.InvokeAsync(interceptingPacketEventArgs).ConfigureAwait(false);
                     currentPacket = interceptingPacketEventArgs.Packet;
                     processPacket = interceptingPacketEventArgs.ProcessPacket;
@@ -579,4 +581,4 @@ public sealed class MqttConnectedClient : IDisposable
             _logger.Warning(exception, "Client '{0}': Error while sending DISCONNECT packet (ReasonCode = {1})", Id, options.ReasonCode);
         }
     }
-}
+}

Source/MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs

@@ -7,13 +7,12 @@ using MQTTnet.Internal;
 
 namespace MQTTnet.Server.Internal;
 
-public sealed class MqttRetainedMessagesManager
+public sealed class MqttRetainedMessagesManager : IDisposable
 {
-    readonly Dictionary<string, MqttApplicationMessage> _messages = new(4096);
-    readonly AsyncLock _storageAccessLock = new();
-
     readonly MqttServerEventContainer _eventContainer;
     readonly MqttNetSourceLogger _logger;
+    readonly Dictionary<string, MqttApplicationMessage> _messages = new(4096);
+    readonly AsyncLock _storageAccessLock = new();
 
     public MqttRetainedMessagesManager(MqttServerEventContainer eventContainer, IMqttNetLogger logger)
     {
@@ -24,6 +23,46 @@ public sealed class MqttRetainedMessagesManager
         _logger = logger.WithSource(nameof(MqttRetainedMessagesManager));
     }
 
+    public async Task ClearMessages()
+    {
+        lock (_messages)
+        {
+            _messages.Clear();
+        }
+
+        using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
+        {
+            await _eventContainer.RetainedMessagesClearedEvent.InvokeAsync(EventArgs.Empty).ConfigureAwait(false);
+        }
+    }
+
+    public void Dispose()
+    {
+        _storageAccessLock.Dispose();
+    }
+
+    public Task<MqttApplicationMessage> GetMessage(string topic)
+    {
+        lock (_messages)
+        {
+            if (_messages.TryGetValue(topic, out var message))
+            {
+                return Task.FromResult(message);
+            }
+        }
+
+        return Task.FromResult<MqttApplicationMessage>(null);
+    }
+
+    public Task<IList<MqttApplicationMessage>> GetMessages()
+    {
+        lock (_messages)
+        {
+            var result = new List<MqttApplicationMessage>(_messages.Values);
+            return Task.FromResult((IList<MqttApplicationMessage>)result);
+        }
+    }
+
     public async Task Start()
     {
         try
@@ -79,8 +118,7 @@ public sealed class MqttRetainedMessagesManager
                     }
                     else
                     {
-                        if (existingMessage.QualityOfServiceLevel != applicationMessage.QualityOfServiceLevel ||
-                            !MqttMemoryHelper.SequenceEqual(existingMessage.Payload, payload))
+                        if (existingMessage.QualityOfServiceLevel != applicationMessage.QualityOfServiceLevel || !MqttMemoryHelper.SequenceEqual(existingMessage.Payload, payload))
                         {
                             _messages[applicationMessage.Topic] = applicationMessage;
                             saveIsRequired = true;
@@ -113,39 +151,4 @@ public sealed class MqttRetainedMessagesManager
             _logger.Error(exception, "Unhandled exception while handling retained messages.");
         }
     }
-
-    public Task<IList<MqttApplicationMessage>> GetMessages()
-    {
-        lock (_messages)
-        {
-            var result = new List<MqttApplicationMessage>(_messages.Values);
-            return Task.FromResult((IList<MqttApplicationMessage>)result);
-        }
-    }
-
-    public Task<MqttApplicationMessage> GetMessage(string topic)
-    {
-        lock (_messages)
-        {
-            if (_messages.TryGetValue(topic, out var message))
-            {
-                return Task.FromResult(message);
-            }
-        }
-
-        return Task.FromResult<MqttApplicationMessage>(null);
-    }
-
-    public async Task ClearMessages()
-    {
-        lock (_messages)
-        {
-            _messages.Clear();
-        }
-
-        using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
-        {
-            await _eventContainer.RetainedMessagesClearedEvent.InvokeAsync(EventArgs.Empty).ConfigureAwait(false);
-        }
-    }
 }

Source/MQTTnet.Server/MQTTnet.Server.csproj

@@ -1,57 +1,19 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
         <AssemblyName>MQTTnet.Server</AssemblyName>
         <RootNamespace>MQTTnet.Server</RootNamespace>
+        <IsAotCompatible>true</IsAotCompatible>
+
         <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
-        <Company>The contributors of MQTTnet</Company>
-        <Product>MQTTnet</Product>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
         <Description>This is the server implementation of MQTTnet.</Description>
-        <Authors>The contributors of MQTTnet</Authors>
         <PackageId>MQTTnet.Server</PackageId>
-        <DelaySign>false</DelaySign>
-        <SignAssembly>false</SignAssembly>
-        <PublishRepositoryUrl>true</PublishRepositoryUrl>
-        <IncludeSymbols>true</IncludeSymbols>
-        <SymbolPackageFormat>snupkg</SymbolPackageFormat>
-        <Copyright>Copyright (c) .NET Foundation and Contributors</Copyright>
-        <PackageProjectUrl>https://github.com/dotnet/MQTTnet</PackageProjectUrl>
-        <RepositoryUrl>https://github.com/dotnet/MQTTnet.git</RepositoryUrl>
-        <RepositoryType>git</RepositoryType>
         <PackageTags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin Blazor</PackageTags>
-        <NeutralLanguage>en-US</NeutralLanguage>
-        <EnableNETAnalyzers>false</EnableNETAnalyzers>
-        <EnforceCodeStyleInBuild>false</EnforceCodeStyleInBuild>
-        <PackageIcon>nuget.png</PackageIcon>
-        <EmbedUntrackedSources>true</EmbedUntrackedSources>
-        <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
-        <PackageLicenseFile>LICENSE</PackageLicenseFile>
-        <DisableImplicitAspNetCoreAnalyzers>true</DisableImplicitAspNetCoreAnalyzers>
-        <NoWarn>1591;NETSDK1138;NU1803;NU1901;NU1902</NoWarn>
-        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-        <NuGetAuditMode>all</NuGetAuditMode>
-        <NuGetAudit>true</NuGetAudit>
-        <NuGetAuditLevel>low</NuGetAuditLevel>
-        <ImplicitUsings>enable</ImplicitUsings>
-        <Nullable>enable</Nullable>
-        <AnalysisLevel>latest-Recommended</AnalysisLevel>
-        <IsAotCompatible>true</IsAotCompatible>
-        <LangVersion>default</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>
         <ProjectReference Include="..\MQTTnet\MQTTnet.csproj"/>
     </ItemGroup>
 
-    <ItemGroup>
-        <None Include="..\..\Images\nuget.png" Pack="true" PackagePath="" />
-        <None Include="..\..\LICENSE" Pack="true" PackagePath="" />
-    </ItemGroup>
-
-    <ItemGroup>
-        <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All"/>
-    </ItemGroup>
-
 </Project>

Source/MQTTnet.Server/MqttServerExtensions.cs

@@ -21,7 +21,7 @@ public static class MqttServerExtensions
     public static Task InjectApplicationMessage(
         this MqttServer server,
         string topic,
-        string? payload = null,
+        string payload = null,
         MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce,
         bool retain = false)
     {

Source/MQTTnet.Server/MqttServerFactory.cs

@@ -2,12 +2,14 @@
 // 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.CodeAnalysis;
 using MQTTnet.Diagnostics.Logger;
 using MQTTnet.Server.EnhancedAuthentication;
 using MQTTnet.Server.Internal.Adapter;
 
 namespace MQTTnet.Server;
 
+[SuppressMessage("Performance", "CA1822:Mark members as static")]
 public sealed class MqttServerFactory
 {
     public MqttServerFactory() : this(new MqttNetNullLogger())

Source/MQTTnet.Server/Options/MqttServerOptionsBuilder.cs

@@ -5,8 +5,8 @@
 using System.Net;
 using System.Net.Security;
 using System.Security.Authentication;
-using MQTTnet.Certificates;
 using System.Security.Cryptography.X509Certificates;
+using MQTTnet.Certificates;
 
 // ReSharper disable UnusedMember.Global
 namespace MQTTnet.Server;
@@ -20,7 +20,7 @@ public class MqttServerOptionsBuilder
         return _options;
     }
 
-    public MqttServerOptionsBuilder WithClientCertificate(RemoteCertificateValidationCallback? validationCallback = null, bool checkCertificateRevocation = false)
+    public MqttServerOptionsBuilder WithClientCertificate(RemoteCertificateValidationCallback validationCallback = null, bool checkCertificateRevocation = false)
     {
         _options.TlsEndpointOptions.ClientCertificateRequired = true;
         _options.TlsEndpointOptions.CheckCertificateRevocation = checkCertificateRevocation;
@@ -47,12 +47,22 @@ public class MqttServerOptionsBuilder
         return this;
     }
 
+    /// <summary>
+    ///     Sets the IPv4 network address to bind.
+    ///     Defaults to any available IPv4 address of the machine.
+    ///     Set this to `IPAddress.None` to disable the IPv4 support entirely.
+    /// </summary>
     public MqttServerOptionsBuilder WithDefaultEndpointBoundIPAddress(IPAddress value)
     {
         _options.DefaultEndpointOptions.BoundInterNetworkAddress = value ?? IPAddress.Any;
         return this;
     }
 
+    /// <summary>
+    ///     Sets the IPv6 network address to bind.
+    ///     Defaults to any available IPv6 address of the machine.
+    ///     Set this to `IPAddress.None` to disable the IPv6 support entirely.
+    /// </summary>
     public MqttServerOptionsBuilder WithDefaultEndpointBoundIPV6Address(IPAddress value)
     {
         _options.DefaultEndpointOptions.BoundInterNetworkV6Address = value ?? IPAddress.Any;
@@ -77,12 +87,22 @@ public class MqttServerOptionsBuilder
         return this;
     }
 
+    /// <summary>
+    ///     Sets the IPv4 network address to bind.
+    ///     Defaults to any available IPv4 address of the machine.
+    ///     Set this to `IPAddress.None` to disable the IPv4 support entirely.
+    /// </summary>
     public MqttServerOptionsBuilder WithEncryptedEndpointBoundIPAddress(IPAddress value)
     {
         _options.TlsEndpointOptions.BoundInterNetworkAddress = value;
         return this;
     }
 
+    /// <summary>
+    ///     Sets the IPv6 network address to bind.
+    ///     Defaults to any available IPv6 address of the machine.
+    ///     Set this to `IPAddress.None` to disable the IPv6 support entirely.
+    /// </summary>
     public MqttServerOptionsBuilder WithEncryptedEndpointBoundIPV6Address(IPAddress value)
     {
         _options.TlsEndpointOptions.BoundInterNetworkV6Address = value;
@@ -95,6 +115,35 @@ public class MqttServerOptionsBuilder
         return this;
     }
 
+    public MqttServerOptionsBuilder WithEncryptionCertificate(byte[] value, IMqttServerCertificateCredentials credentials = null)
+    {
+        ArgumentNullException.ThrowIfNull(value);
+
+        _options.TlsEndpointOptions.CertificateProvider = new BlobCertificateProvider(value)
+        {
+            Password = credentials?.Password
+        };
+
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptionCertificate(X509Certificate2 certificate)
+    {
+        ArgumentNullException.ThrowIfNull(certificate);
+
+        _options.TlsEndpointOptions.CertificateProvider = new X509CertificateProvider(certificate);
+        return this;
+    }
+
+    public MqttServerOptionsBuilder WithEncryptionCertificate(ICertificateProvider certificateProvider)
+    {
+        ArgumentNullException.ThrowIfNull(certificateProvider);
+
+        _options.TlsEndpointOptions.CertificateProvider = certificateProvider;
+
+        return this;
+    }
+
     public MqttServerOptionsBuilder WithEncryptionSslProtocol(SslProtocols value)
     {
         _options.TlsEndpointOptions.SslProtocol = value;
@@ -114,12 +163,6 @@ public class MqttServerOptionsBuilder
         return this;
     }
 
-    public MqttServerOptionsBuilder WithPendingMessagesOverflowStrategy(MqttPendingMessagesOverflowStrategy value)
-    {
-        _options.PendingMessagesOverflowStrategy = value;
-        return this;
-    }
-
     public MqttServerOptionsBuilder WithoutDefaultEndpoint()
     {
         _options.DefaultEndpointOptions.IsEnabled = false;
@@ -144,6 +187,12 @@ public class MqttServerOptionsBuilder
         return this;
     }
 
+    public MqttServerOptionsBuilder WithPendingMessagesOverflowStrategy(MqttPendingMessagesOverflowStrategy value)
+    {
+        _options.PendingMessagesOverflowStrategy = value;
+        return this;
+    }
+
     public MqttServerOptionsBuilder WithPersistentSessions(bool value = true)
     {
         _options.EnablePersistentSessions = value;
@@ -182,33 +231,4 @@ public class MqttServerOptionsBuilder
         _options.TlsEndpointOptions.ReuseAddress = true;
         return this;
     }
-
-    public MqttServerOptionsBuilder WithEncryptionCertificate(byte[] value, IMqttServerCertificateCredentials? credentials = null)
-    {
-        ArgumentNullException.ThrowIfNull(value);
-
-        _options.TlsEndpointOptions.CertificateProvider = new BlobCertificateProvider(value)
-        {
-            Password = credentials?.Password
-        };
-
-        return this;
-    }
-
-    public MqttServerOptionsBuilder WithEncryptionCertificate(X509Certificate2 certificate)
-    {
-        ArgumentNullException.ThrowIfNull(certificate);
-
-        _options.TlsEndpointOptions.CertificateProvider = new X509CertificateProvider(certificate);
-        return this;
-    }
-
-    public MqttServerOptionsBuilder WithEncryptionCertificate(ICertificateProvider certificateProvider)
-    {
-        ArgumentNullException.ThrowIfNull(certificateProvider);
-
-        _options.TlsEndpointOptions.CertificateProvider = certificateProvider;
-
-        return this;
-    }
 }

Source/MQTTnet.Server/Options/MqttServerTcpEndpointBaseOptions.cs

@@ -9,13 +9,30 @@ namespace MQTTnet.Server;
 
 public abstract class MqttServerTcpEndpointBaseOptions
 {
-    public bool IsEnabled { get; set; }
+    /// <summary>
+    ///     Usually the MQTT packets can be sent partially. This is done by using multiple TCP packets
+    ///     or WebSocket frames etc. Unfortunately not all clients do support this feature and
+    ///     will close the connection when receiving such packets. If such clients are connecting to this
+    ///     server the flag must be set to _false_.
+    /// </summary>
+    public bool AllowPacketFragmentation { get; set; } = true;
 
-    public int Port { get; set; }
+    /// <summary>
+    ///     Gets or sets the IPv4 network address to bind.
+    ///     Defaults to any available IPv4 address of the machine.
+    ///     Set this to `IPAddress.None` to disable the IPv4 support entirely.
+    /// </summary>
+    public IPAddress BoundInterNetworkAddress { get; set; } = IPAddress.Any;
+
+    /// <summary>
+    ///     Gets or sets the IPv6 network address to bind.
+    ///     Defaults to any available IPv6 address of the machine.
+    ///     Set this to `IPAddress.None` to disable the IPv6 support entirely.
+    /// </summary>
+    public IPAddress BoundInterNetworkV6Address { get; set; } = IPAddress.IPv6Any;
 
     public int ConnectionBacklog { get; set; } = 100;
-
-    public bool NoDelay { get; set; } = true;
+    public bool IsEnabled { get; set; }
 
     /// <summary>
     ///     Gets or sets whether the sockets keep alive feature should be used.
@@ -23,13 +40,16 @@ public abstract class MqttServerTcpEndpointBaseOptions
     /// </summary>
     public bool? KeepAlive { get; set; }
 
+    public LingerOption LingerState { get; set; } = new(true, 0);
+
+    public bool NoDelay { get; set; } = true;
+
+    public int Port { get; set; }
+
     /// <summary>
-    ///     Usually the MQTT packets can be send partially. This is done by using multiple TCP packets
-    ///     or WebSocket frames etc. Unfortunately not all clients do support this feature and
-    ///     will close the connection when receiving such packets. If such clients are connecting to this
-    ///     server the flag must be set to _false_.
+    ///     This requires admin permissions on Linux.
     /// </summary>
-    public bool AllowPacketFragmentation { get; set; } = true;
+    public bool ReuseAddress { get; set; }
 
     /// <summary>
     ///     Gets or sets the TCP keep alive interval.
@@ -48,15 +68,4 @@ public abstract class MqttServerTcpEndpointBaseOptions
     ///     The value _null_ indicates that the OS and framework defaults should be used.
     /// </summary>
     public int? TcpKeepAliveTime { get; set; }
-
-    public LingerOption LingerState { get; set; } = new LingerOption(true, 0);
-
-    public IPAddress BoundInterNetworkAddress { get; set; } = IPAddress.Any;
-
-    public IPAddress BoundInterNetworkV6Address { get; set; } = IPAddress.IPv6Any;
-
-    /// <summary>
-    ///     This requires admin permissions on Linux.
-    /// </summary>
-    public bool ReuseAddress { get; set; }
 }

Source/MQTTnet.Server/SubscribeResponse.cs

@@ -16,7 +16,7 @@ public sealed class SubscribeResponse
     /// </summary>
     public MqttSubscribeReasonCode ReasonCode { get; set; }
 
-    public string? ReasonString { get; set; }
+    public string ReasonString { get; set; }
 
-    public List<MqttUserProperty>? UserProperties { get; set; } = [];
+    public List<MqttUserProperty> UserProperties { get; } = [];
 }

Source/MQTTnet.Server/UnsubscribeResponse.cs

@@ -15,7 +15,7 @@ public sealed class UnsubscribeResponse
     /// </summary>
     public MqttUnsubscribeReasonCode ReasonCode { get; set; }
 
-    public string? ReasonString { get; set; }
+    public string ReasonString { get; set; }
 
-    public List<MqttUserProperty>? UserProperties { get; } = [];
+    public List<MqttUserProperty> UserProperties { get; } = [];
 }