Merge branch 'develop'

Merge fixes

.gitignore

@@ -1,5 +1,7 @@
 ## Ignore Visual Studio temporary files, build results, and
 ## files generated by popular Visual Studio add-ons.
+##
+## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore
 
 # User-specific files
 *.suo
@@ -15,12 +17,12 @@
 [Dd]ebugPublic/
 [Rr]elease/
 [Rr]eleases/
-[Xx]64/
-[Xx]86/
-[Bb]uild/
+x64/
+x86/
 bld/
 [Bb]in/
 [Oo]bj/
+[Ll]og/
 
 # Visual Studio 2015 cache/options directory
 .vs/
@@ -40,9 +42,11 @@ TestResult.xml
 [Rr]eleasePS/
 dlldata.c
 
-# DNX
+# .NET Core
 project.lock.json
+project.fragment.lock.json
 artifacts/
+**/Properties/launchSettings.json
 
 *_i.c
 *_p.c
@@ -81,6 +85,7 @@ ipch/
 *.sdf
 *.cachefile
 *.VC.db
+*.VC.VC.opendb
 
 # Visual Studio profiler
 *.psess
@@ -108,6 +113,10 @@ _TeamCity*
 # DotCover is a Code Coverage Tool
 *.dotCover
 
+# Visual Studio code coverage results
+*.coverage
+*.coveragexml
+
 # NCrunch
 _NCrunch_*
 .*crunch*.local.xml
@@ -139,13 +148,16 @@ publish/
 # Publish Web Output
 *.[Pp]ublish.xml
 *.azurePubxml
-
-# TODO: Un-comment the next line if you do not want to checkin 
-# your web deploy settings because they may include unencrypted
-# passwords
-#*.pubxml
+# TODO: Comment the next line if you want to checkin your web deploy settings
+# but database connection strings (with potential passwords) will be unencrypted
+*.pubxml
 *.publishproj
 
+# Microsoft Azure Web App publish settings. Comment the next line if you want to
+# checkin your Azure Web App publish settings, but sensitive information contained
+# in these scripts will be unencrypted
+PublishScripts/
+
 # NuGet Packages
 *.nupkg
 # The packages folder can be ignored because of Package Restore
@@ -154,7 +166,7 @@ publish/
 !**/packages/build/
 # Uncomment if necessary however generally it will be regenerated when needed
 #!**/packages/repositories.config
-# NuGet v3's project.json files produces more ignoreable files
+# NuGet v3's project.json files produces more ignorable files
 *.nuget.props
 *.nuget.targets
 
@@ -166,12 +178,11 @@ csx/
 ecf/
 rcf/
 
-# Microsoft Azure ApplicationInsights config file
-ApplicationInsights.config
-
-# Windows Store app package directory
+# Windows Store app package directories and files
 AppPackages/
 BundleArtifacts/
+Package.StoreAssociation.xml
+_pkginfo.txt
 
 # Visual Studio cache files
 # files ending in .cache can be ignored
@@ -181,16 +192,19 @@ BundleArtifacts/
 
 # Others
 ClientBin/
-[Ss]tyle[Cc]op.*
 ~$*
 *~
 *.dbmdl
 *.dbproj.schemaview
+*.jfm
 *.pfx
 *.publishsettings
-node_modules/
 orleans.codegen.cs
 
+# Since there are multiple workflows, uncomment next line to ignore bower_components
+# (https://github.com/github/gitignore/pull/1529#issuecomment-104372622)
+#bower_components/
+
 # RIA/Silverlight projects
 Generated_Code/
 
@@ -205,6 +219,7 @@ UpgradeLog*.htm
 # SQL Server files
 *.mdf
 *.ldf
+*.ndf
 
 # Business Intelligence projects
 *.rdl.data
@@ -219,6 +234,10 @@ FakesAssemblies/
 
 # Node.js Tools for Visual Studio
 .ntvs_analysis.dat
+node_modules/
+
+# Typescript v1 declaration files
+typings/
 
 # Visual Studio 6 build log
 *.plg
@@ -226,6 +245,9 @@ FakesAssemblies/
 # Visual Studio 6 workspace options file
 *.opt
 
+# Visual Studio 6 auto-generated workspace file (contains which files were open etc.)
+*.vbw
+
 # Visual Studio LightSwitch build output
 **/*.HTMLClient/GeneratedArtifacts
 **/*.DesktopClient/GeneratedArtifacts
@@ -234,12 +256,34 @@ FakesAssemblies/
 **/*.Server/ModelManifest.xml
 _Pvt_Extensions
 
-# LightSwitch generated files
-GeneratedArtifacts/
-ModelManifest.xml
-
 # Paket dependency manager
 .paket/paket.exe
+paket-files/
 
 # FAKE - F# Make
-.fake/
+.fake/
+
+# JetBrains Rider
+.idea/
+*.sln.iml
+
+# CodeRush
+.cr/
+
+# Python Tools for Visual Studio (PTVS)
+__pycache__/
+*.pyc
+
+# Cake - Uncomment if you are using it
+# tools/**
+# !tools/packages.config
+
+# Telerik's JustMock configuration file
+*.jmconfig
+
+# BizTalk build output
+*.btp.cs
+*.btm.cs
+*.odx.cs
+*.xsd.cs
+Build/nuget.exe

Build/MQTTnet.nuspec

@@ -0,0 +1,49 @@
+<?xml version="1.0"?>
+<package >
+  <metadata>
+    <id>MQTTnet</id>
+    <version>2.1.5</version>
+    <authors>Christian Kratky</authors>
+    <owners>Christian Kratky</owners>
+    <licenseUrl>https://github.com/chkr1011/MQTTnet/blob/master/LICENSE</licenseUrl>
+    <projectUrl>https://github.com/chkr1011/MQTTnet</projectUrl>
+    <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
+    <requireLicenseAcceptance>false</requireLicenseAcceptance>
+    <description>MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker).</description>
+    <releaseNotes>* [MqttServer] Added support for publishing application messages
+* [Core] Fixed QoS level 2 handling
+* [Core] Performance optimizations
+* [MqttClient/MqttServer] Errors while handline application messages are now catched and traced
+* [MqttClient/MqttServer] Added interfaces
+    </releaseNotes>
+    <copyright>Copyright Christian Kratky 2016-2017</copyright>
+    <tags>MQTT MQTTClient MQTTServer MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Queue Hardware</tags> 
+    <dependencies>
+
+      <group targetFramework="netstandard1.3">
+        <dependency id="NETStandard.Library" version="1.6.1" />
+        <dependency id="System.Net.Security" version="4.3.1" />
+      </group>
+      
+      <group targetFramework="uap10.0">
+        <dependency id="Microsoft.NETCore.UniversalWindowsPlatform" version="5.3.3" />
+      </group>
+
+    </dependencies>
+  </metadata>
+
+  <files>
+    <!-- .NET Standard 1.3 -->
+    <file src="..\Frameworks\MQTTnet.Netstandard\bin\Release\netstandard1.3\MQTTnet.Core.*" target="lib\netstandard1.3\"/>
+    <file src="..\Frameworks\MQTTnet.Netstandard\bin\Release\netstandard1.3\MQTTnet.*" target="lib\netstandard1.3\"/>
+
+    <!-- Universal Windows -->
+    <file src="..\Frameworks\MQTTnet.UniversalWindows\bin\Release\MQTTnet.Core.*" target="lib\uap10.0\"/>
+    <file src="..\Frameworks\MQTTnet.UniversalWindows\bin\Release\MQTTnet.*" target="lib\uap10.0\"/>
+
+    <!-- .NET Framework -->
+    <file src="..\Frameworks\MQTTnet.NetFramework\bin\Release\MQTTnet.Core.*" target="lib\net45\"/>
+    <file src="..\Frameworks\MQTTnet.NetFramework\bin\Release\MQTTnet.*" target="lib\net45\"/>
+    
+  </files>
+</package>

Build/build.ps1

@@ -0,0 +1,12 @@
+param([string]$version)
+
+if ([string]::IsNullOrEmpty($version)) {$version = "0.0.1"}
+
+$msbuild = "MSBuild.exe"
+&$msbuild ..\Frameworks\MQTTnet.NetFramework\MQTTnet.NetFramework.csproj /t:Build /p:Configuration="Release"
+&$msbuild ..\Frameworks\MQTTnet.Netstandard\MQTTnet.Netstandard.csproj /t:Build /p:Configuration="Release"
+&$msbuild ..\Frameworks\MQTTnet.UniversalWindows\MQTTnet.UniversalWindows.csproj /t:Build /p:Configuration="Release"
+
+Remove-Item .\NuGet -Force -Recurse
+New-Item -ItemType Directory -Force -Path .\NuGet
+.\NuGet.exe pack MQTTnet.nuspec -Verbosity detailed -Symbols -OutputDir "NuGet" -Version $version

Frameworks/MQTTnet.NetCore/MQTTnet.NetCore.csproj

@@ -1,23 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-    <TargetFramework>netcoreapp1.1</TargetFramework>
-    <Authors>Christian Kratky</Authors>
-    <Company>Christian Kratky</Company>
-    <Product>MQTTnet</Product>
-    <Description>MQTTnet for .NET Core</Description>
-    <Copyright>Copyright © Christian Kratky 2016-2017</Copyright>
-    <Version>2.0.4.0</Version>
-    <AssemblyVersion>2.0.4.0</AssemblyVersion>
-    <FileVersion>2.0.4.0</FileVersion>
-    <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
-    <AssemblyName>MQTTnet</AssemblyName>
-    <RootNamespace>MQTTnet</RootNamespace>
-    <PackageId>MQTTnet</PackageId>
-  </PropertyGroup>
-
-  <ItemGroup>
-    <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj" />
-  </ItemGroup>
-
-</Project>

Frameworks/MQTTnet.NetCore/MqttServerAdapter.cs

@@ -1,56 +0,0 @@
-using System;
-using System.Net;
-using System.Net.Sockets;
-using System.Threading;
-using System.Threading.Tasks;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Serializer;
-using MQTTnet.Core.Server;
-
-namespace MQTTnet
-{
-    public sealed class MqttServerAdapter : IMqttServerAdapter, IDisposable
-    {
-        private CancellationTokenSource _cancellationTokenSource;
-        private Socket _socket;
-
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
-
-        public void Start(MqttServerOptions options)
-        {
-            if (_socket != null) throw new InvalidOperationException("Server is already started.");
-
-            _cancellationTokenSource = new CancellationTokenSource();
-
-            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
-            _socket.Bind(new IPEndPoint(IPAddress.Any, options.Port));
-            _socket.Listen(options.ConnectionBacklog);
-            
-            Task.Run(async () => await AcceptConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
-        }
-
-        public void Stop()
-        {
-            _cancellationTokenSource?.Dispose();
-            _cancellationTokenSource = null;
-
-            _socket?.Dispose();
-            _socket = null;
-        }
-
-        public void Dispose()
-        {
-            Stop();
-        }
-
-        private async Task AcceptConnectionsAsync(CancellationToken cancellationToken)
-        {
-            while (!cancellationToken.IsCancellationRequested)
-            {
-                var clientSocket = await _socket.AcceptAsync();
-                var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket), new DefaultMqttV311PacketSerializer());    
-                ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
-            }
-        }
-    }
-}

Frameworks/MQTTnet.NetCore/MqttServerFactory.cs

@@ -1,15 +0,0 @@
-using System;
-using MQTTnet.Core.Server;
-
-namespace MQTTnet
-{
-    public class MqttServerFactory
-    {
-        public MqttServer CreateMqttServer(MqttServerOptions options)
-        {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-
-            return new MqttServer(options, new MqttServerAdapter());
-        }
-    }
-}

Frameworks/MQTTnet.NetCore/MqttTcpChannel.cs

@@ -1,81 +0,0 @@
-using System;
-using System.Net.Sockets;
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
-using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
-
-namespace MQTTnet
-{
-    public class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
-    {
-        private readonly Socket _socket;
-
-        public MqttTcpChannel()
-        {
-            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
-        }
-
-        public MqttTcpChannel(Socket socket)
-        {
-            _socket = socket ?? throw new ArgumentNullException(nameof(socket));
-        }
-
-        public async Task ConnectAsync(MqttClientOptions options)
-        {
-            try
-            {
-                await _socket.ConnectAsync(options.Server, options.Port);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task DisconnectAsync()
-        {
-            try
-            {
-                _socket.Dispose();
-                await Task.FromResult(0);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                await _socket.SendAsync(new ArraySegment<byte>(buffer), SocketFlags.None);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task ReadAsync(byte[] buffer)
-        {
-            try
-            {
-                var buffer2 = new ArraySegment<byte>(buffer);
-                await _socket.ReceiveAsync(buffer2, SocketFlags.None);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public void Dispose()
-        {
-            _socket?.Dispose();
-        }
-    }
-}

Frameworks/MQTTnet.NetFramework/Implementations/MqttServerAdapter.cs

@@ -0,0 +1,120 @@
+using System;
+using System.Net;
+using System.Net.Security;
+using System.Net.Sockets;
+using System.Security.Authentication;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading;
+using System.Threading.Tasks;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Serializer;
+using MQTTnet.Core.Server;
+
+namespace MQTTnet.Implementations
+{
+    public class MqttServerAdapter : IMqttServerAdapter, IDisposable
+    {
+        private CancellationTokenSource _cancellationTokenSource;
+        private Socket _defaultEndpointSocket;
+        private Socket _tlsEndpointSocket;
+        private X509Certificate2 _tlsCertificate;
+
+        private bool _isRunning;
+
+        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+
+        public void Start(MqttServerOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (_isRunning) throw new InvalidOperationException("Server is already started.");
+            _isRunning = true;
+
+            _cancellationTokenSource = new CancellationTokenSource();
+
+            if (options.DefaultEndpointOptions.IsEnabled)
+            {
+                _defaultEndpointSocket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+                _defaultEndpointSocket.Bind(new IPEndPoint(IPAddress.Any, options.GetDefaultEndpointPort()));
+                _defaultEndpointSocket.Listen(options.ConnectionBacklog);
+
+                Task.Run(() => AcceptDefaultEndpointConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+            }
+
+            if (options.TlsEndpointOptions.IsEnabled)
+            {
+                if (options.TlsEndpointOptions.Certificate == null)
+                {
+                    throw new ArgumentException("TLS certificate is not set.");
+                }
+
+                _tlsCertificate = new X509Certificate2(options.TlsEndpointOptions.Certificate);
+
+                _tlsEndpointSocket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+                _tlsEndpointSocket.Bind(new IPEndPoint(IPAddress.Any, options.GetTlsEndpointPort()));
+                _tlsEndpointSocket.Listen(options.ConnectionBacklog);
+
+                Task.Run(() => AcceptTlsEndpointConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+            }
+        }
+
+        public void Stop()
+        {
+            _isRunning = false;
+
+            _cancellationTokenSource?.Cancel(false);
+            _cancellationTokenSource?.Dispose();
+            _cancellationTokenSource = null;
+
+            _defaultEndpointSocket?.Dispose();
+            _defaultEndpointSocket = null;
+
+            _tlsEndpointSocket?.Dispose();
+            _tlsEndpointSocket = null;
+        }
+
+        public void Dispose()
+        {
+            Stop();
+        }
+
+        private async Task AcceptDefaultEndpointConnectionsAsync(CancellationToken cancellationToken)
+        {
+            while (!cancellationToken.IsCancellationRequested)
+            {
+                try
+                {
+                    var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, null), new DefaultMqttV311PacketSerializer());
+                    ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
+                }
+                catch (Exception exception) when (!(exception is ObjectDisposedException))
+                {
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at default endpoint.");
+                }
+            }
+        }
+
+        private async Task AcceptTlsEndpointConnectionsAsync(CancellationToken cancellationToken)
+        {
+            while (!cancellationToken.IsCancellationRequested)
+            {
+                try
+                {
+                    var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null);
+
+                    var sslStream = new SslStream(new NetworkStream(clientSocket));
+                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false);
+                    
+                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, sslStream), new DefaultMqttV311PacketSerializer());
+                    ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
+                }
+                catch (Exception exception)
+                {
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at TLS endpoint.");
+                }
+            }
+        }
+    }
+}

Frameworks/MQTTnet.NetFramework/Implementations/MqttTcpChannel.cs

@@ -0,0 +1,129 @@
+using System;
+using System.Net.Security;
+using System.Net.Sockets;
+using System.Security.Authentication;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading.Tasks;
+using MQTTnet.Core.Channel;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Exceptions;
+
+namespace MQTTnet.Implementations
+{
+    public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private readonly Socket _socket;
+        private SslStream _sslStream;
+
+        public MqttTcpChannel()
+        {
+            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+        }
+
+        public MqttTcpChannel(Socket socket, SslStream sslStream)
+        {
+            _socket = socket ?? throw new ArgumentNullException(nameof(socket));
+            _sslStream = sslStream;
+        }
+
+        public async Task ConnectAsync(MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+            try
+            {
+                await Task.Factory.FromAsync(_socket.BeginConnect, _socket.EndConnect, options.Server, options.GetPort(), null);
+
+                if (options.TlsOptions.UseTls)
+                {
+                    _sslStream = new SslStream(new NetworkStream(_socket, true));
+                    await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation);
+                }
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task DisconnectAsync()
+        {
+            try
+            {
+                _sslStream.Dispose();
+                _socket.Dispose();
+                return Task.FromResult(0);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task WriteAsync(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+
+            try
+            {
+                if (_sslStream != null)
+                {
+                    return _sslStream.WriteAsync(buffer, 0, buffer.Length);
+                }
+
+                return Task.Factory.FromAsync(
+                    // ReSharper disable once AssignNullToNotNullAttribute
+                    _socket.BeginSend(buffer, 0, buffer.Length, SocketFlags.None, null, null),
+                    _socket.EndSend);
+
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task ReadAsync(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+
+            try
+            {
+                if (_sslStream != null)
+                {
+                    return _sslStream.ReadAsync(buffer, 0, buffer.Length);
+                }
+
+                return Task.Factory.FromAsync(
+                    // ReSharper disable once AssignNullToNotNullAttribute
+                    _socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, null, null),
+                    _socket.EndReceive);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public void Dispose()
+        {
+            _socket?.Dispose();
+            _sslStream?.Dispose();
+        }
+
+        private static X509CertificateCollection LoadCertificates(MqttClientOptions options)
+        {
+            var certificates = new X509CertificateCollection();
+            if (options.TlsOptions.Certificates == null)
+            {
+                return certificates;
+            }
+
+            foreach (var certificate in options.TlsOptions.Certificates)
+            {
+                certificates.Add(new X509Certificate(certificate));
+            }
+
+            return certificates;
+        }
+    }
+}

Frameworks/MQTTnet.NetFramework/MQTTnet.NetFramework.csproj

@@ -32,20 +32,83 @@
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|AnyCPU'">
+    <OutputPath>bin\Any CPU\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
+    <DebugSymbols>true</DebugSymbols>
+    <OutputPath>bin\x86\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <DebugType>full</DebugType>
+    <PlatformTarget>x86</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x86'">
+    <OutputPath>bin\x86\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x86</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x86'">
+    <OutputPath>bin\x86\Any CPU\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x86</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
+    <DebugSymbols>true</DebugSymbols>
+    <OutputPath>bin\x64\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <DebugType>full</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
+    <OutputPath>bin\x64\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x64'">
+    <OutputPath>bin\x64\Any CPU\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
     <Reference Include="System.Core" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="MqttClientFactory.cs" />
-    <Compile Include="MqttServerAdapter.cs" />
     <Compile Include="MqttServerFactory.cs" />
+    <Compile Include="Implementations\MqttServerAdapter.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="MqttTcpChannel.cs" />
+    <Compile Include="Implementations\MqttTcpChannel.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj">
-      <Project>{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}</Project>
+      <Project>{2ecb99e4-72d0-4c23-99ba-93d511d3967d}</Project>
       <Name>MQTTnet.Core</Name>
     </ProjectReference>
   </ItemGroup>

Frameworks/MQTTnet.NetFramework/MqttClientFactory.cs

@@ -2,16 +2,17 @@
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Serializer;
+using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
     public class MqttClientFactory
     {
-        public MqttClient CreateMqttClient(MqttClientOptions options)
+        public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
             return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new DefaultMqttV311PacketSerializer()));
         }
     }
-}
+}

Frameworks/MQTTnet.NetFramework/MqttServerAdapter.cs

@@ -1,56 +0,0 @@
-using System;
-using System.Net;
-using System.Net.Sockets;
-using System.Threading;
-using System.Threading.Tasks;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Serializer;
-using MQTTnet.Core.Server;
-
-namespace MQTTnet
-{
-    public sealed class MqttServerAdapter : IMqttServerAdapter, IDisposable
-    {
-        private CancellationTokenSource _cancellationTokenSource;
-        private Socket _socket;
-
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
-
-        public void Start(MqttServerOptions options)
-        {
-            if (_socket != null) throw new InvalidOperationException("Server is already started.");
-
-            _cancellationTokenSource = new CancellationTokenSource();
-
-            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
-            _socket.Bind(new IPEndPoint(IPAddress.Any, options.Port));
-            _socket.Listen(options.ConnectionBacklog);
-            
-            Task.Run(async () => await AcceptConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
-        }
-
-        public void Stop()
-        {
-            _cancellationTokenSource?.Dispose();
-            _cancellationTokenSource = null;
-
-            _socket?.Dispose();
-            _socket = null;
-        }
-
-        public void Dispose()
-        {
-            Stop();
-        }
-
-        private async Task AcceptConnectionsAsync(CancellationToken cancellationToken)
-        {
-            while (!cancellationToken.IsCancellationRequested)
-            {
-                var clientSocket = await Task.Factory.FromAsync(_socket.BeginAccept, _socket.EndAccept, null);
-                var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket), new DefaultMqttV311PacketSerializer());    
-                ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
-            }
-        }
-    }
-}

Frameworks/MQTTnet.NetFramework/MqttServerFactory.cs

@@ -1,15 +1,18 @@
 using System;
+using System.Collections.Generic;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Server;
+using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
     public class MqttServerFactory
     {
-        public MqttServer CreateMqttServer(MqttServerOptions options)
+        public IMqttServer CreateMqttServer(MqttServerOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
-            return new MqttServer(options, new MqttServerAdapter());
+            return new MqttServer(options, new List<IMqttServerAdapter> { new MqttServerAdapter() });
         }
     }
 }

Frameworks/MQTTnet.NetFramework/MqttTcpChannel.cs

@@ -1,85 +0,0 @@
-using System;
-using System.Net.Sockets;
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
-using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
-
-namespace MQTTnet
-{
-    public class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
-    {
-        private readonly Socket _socket;
-
-        public MqttTcpChannel()
-        {
-            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
-        }
-
-        public MqttTcpChannel(Socket socket)
-        {
-            _socket = socket ?? throw new ArgumentNullException(nameof(socket));
-        }
-
-        public async Task ConnectAsync(MqttClientOptions options)
-        {
-            try
-            {
-                await Task.Factory.FromAsync(_socket.BeginConnect, _socket.EndConnect, options.Server, options.Port, null);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task DisconnectAsync()
-        {
-            try
-            {
-                await Task.Factory.FromAsync(_socket.BeginDisconnect, _socket.EndDisconnect, true, null);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                await Task.Factory.FromAsync(
-                    // ReSharper disable once AssignNullToNotNullAttribute
-                    _socket.BeginSend(buffer, 0, buffer.Length, SocketFlags.None, null, null),
-                    _socket.EndSend);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task ReadAsync(byte[] buffer)
-        {
-            try
-            {
-                await Task.Factory.FromAsync(
-                    // ReSharper disable once AssignNullToNotNullAttribute
-                    _socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, null, null),
-                    _socket.EndReceive);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public void Dispose()
-        {
-            _socket?.Dispose();
-        }
-    }
-}

Frameworks/MQTTnet.NetFramework/Properties/AssemblyInfo.cs

@@ -11,5 +11,5 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyCulture("")]
 [assembly: ComVisible(false)]
 [assembly: Guid("a480ef90-0eaa-4d9a-b271-47a9c47f6f7d")]
-[assembly: AssemblyVersion("2.1.0.4")]
-[assembly: AssemblyFileVersion("2.1.0.4")]
+[assembly: AssemblyVersion("2.1.4.0")]
+[assembly: AssemblyFileVersion("2.1.4.0")]

Frameworks/MQTTnet.NetStandard/Implementations/MqttServerAdapter.cs

@@ -0,0 +1,118 @@
+using System;
+using System.Net;
+using System.Net.Security;
+using System.Net.Sockets;
+using System.Security.Authentication;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading;
+using System.Threading.Tasks;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Serializer;
+using MQTTnet.Core.Server;
+
+namespace MQTTnet.Implementations
+{
+    public class MqttServerAdapter : IMqttServerAdapter, IDisposable
+    {
+        private CancellationTokenSource _cancellationTokenSource;
+        private Socket _defaultEndpointSocket;
+        private Socket _tlsEndpointSocket;
+        private X509Certificate2 _tlsCertificate;
+
+        private bool _isRunning;
+
+        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+
+        public void Start(MqttServerOptions options)
+        {
+            if (_isRunning) throw new InvalidOperationException("Server is already started.");
+            _isRunning = true;
+
+            _cancellationTokenSource = new CancellationTokenSource();
+
+            if (options.DefaultEndpointOptions.IsEnabled)
+            {
+                _defaultEndpointSocket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+                _defaultEndpointSocket.Bind(new IPEndPoint(IPAddress.Any, options.GetDefaultEndpointPort()));
+                _defaultEndpointSocket.Listen(options.ConnectionBacklog);
+
+                Task.Run(() => AcceptDefaultEndpointConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+            }
+
+            if (options.TlsEndpointOptions.IsEnabled)
+            {
+                if (options.TlsEndpointOptions.Certificate == null)
+                {
+                    throw new ArgumentException("TLS certificate is not set.");
+                }
+
+                _tlsCertificate = new X509Certificate2(options.TlsEndpointOptions.Certificate);
+
+                _tlsEndpointSocket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+                _tlsEndpointSocket.Bind(new IPEndPoint(IPAddress.Any, options.GetTlsEndpointPort()));
+                _tlsEndpointSocket.Listen(options.ConnectionBacklog);
+
+                Task.Run(() => AcceptTlsEndpointConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+            }
+        }
+
+        public void Stop()
+        {
+            _isRunning = false;
+
+            _cancellationTokenSource?.Cancel(false);
+            _cancellationTokenSource?.Dispose();
+            _cancellationTokenSource = null;
+
+            _defaultEndpointSocket?.Dispose();
+            _defaultEndpointSocket = null;
+
+            _tlsEndpointSocket?.Dispose();
+            _tlsEndpointSocket = null;
+        }
+
+        public void Dispose()
+        {
+            Stop();
+        }
+
+        private async Task AcceptDefaultEndpointConnectionsAsync(CancellationToken cancellationToken)
+        {
+            while (!cancellationToken.IsCancellationRequested)
+            {
+                try
+                {
+                    var clientSocket = await _defaultEndpointSocket.AcceptAsync();
+                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, null), new DefaultMqttV311PacketSerializer());
+                    ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
+                }
+                catch (Exception exception)
+                {
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at default endpoint.");
+                }
+            }
+        }
+
+        private async Task AcceptTlsEndpointConnectionsAsync(CancellationToken cancellationToken)
+        {
+            while (!cancellationToken.IsCancellationRequested)
+            {
+                try
+                {
+                    var clientSocket = await _defaultEndpointSocket.AcceptAsync();
+
+                    var sslStream = new SslStream(new NetworkStream(clientSocket));
+                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false);
+                    
+                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, sslStream), new DefaultMqttV311PacketSerializer());
+                    ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
+                }
+                catch (Exception exception)
+                {
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at TLS endpoint.");
+                }
+            }
+        }
+    }
+}

Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs

@@ -0,0 +1,122 @@
+using System;
+using System.Net.Security;
+using System.Net.Sockets;
+using System.Security.Authentication;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading.Tasks;
+using MQTTnet.Core.Channel;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Exceptions;
+
+namespace MQTTnet.Implementations
+{
+    public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private readonly Socket _socket;
+        private SslStream _sslStream;
+
+        public MqttTcpChannel()
+        {
+            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+        }
+
+        public MqttTcpChannel(Socket socket, SslStream sslStream)
+        {
+            _socket = socket ?? throw new ArgumentNullException(nameof(socket));
+            _sslStream = sslStream;
+        }
+
+        public async Task ConnectAsync(MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+            try
+            {
+                await _socket.ConnectAsync(options.Server, options.GetPort());
+                
+                if (options.TlsOptions.UseTls)
+                {
+                    _sslStream = new SslStream(new NetworkStream(_socket, true));
+                    await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation);
+                }
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task DisconnectAsync()
+        {
+            try
+            {
+                _sslStream.Dispose();
+                _socket.Dispose();
+                return Task.FromResult(0);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task WriteAsync(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+
+            try
+            {
+                if (_sslStream != null)
+                {
+                    return _sslStream.WriteAsync(buffer, 0, buffer.Length);
+                }
+
+                return _socket.SendAsync(new ArraySegment<byte>(buffer), SocketFlags.None);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task ReadAsync(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+
+            try
+            {
+                if (_sslStream != null)
+                {
+                    return _sslStream.ReadAsync(buffer, 0, buffer.Length);
+                }
+
+                return _socket.ReceiveAsync(new ArraySegment<byte>(buffer), SocketFlags.None);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public void Dispose()
+        {
+            _socket?.Dispose();
+            _sslStream?.Dispose();
+        }
+
+        private static X509CertificateCollection LoadCertificates(MqttClientOptions options)
+        {
+            var certificates = new X509CertificateCollection();
+            if (options.TlsOptions.Certificates == null)
+            {
+                return certificates;
+            }
+
+            foreach (var certificate in options.TlsOptions.Certificates)
+            {
+                certificates.Add(new X509Certificate(certificate));
+            }
+
+            return certificates;
+        }
+    }
+}

Frameworks/MQTTnet.NetStandard/MQTTnet.Netstandard.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard1.3</TargetFramework>
+    <AssemblyName>MQTTnet</AssemblyName>
+    <RootNamespace>MQTTnet</RootNamespace>
+    <AssemblyVersion>2.1.4.0</AssemblyVersion>
+    <FileVersion>2.1.4.0</FileVersion>
+    <Version>0.0.0.0</Version>
+    <Company />
+    <Product />
+    <Description />
+    <Authors />
+    <PackageId />
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x86'" />
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" />
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="System.Net.Security" Version="4.3.1" />
+  </ItemGroup>
+
+</Project>

Frameworks/MQTTnet.NetStandard/MqttClientFactory.cs

@@ -2,12 +2,13 @@
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Serializer;
+using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
     public class MqttClientFactory
     {
-        public MqttClient CreateMqttClient(MqttClientOptions options)
+        public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 

Frameworks/MQTTnet.NetStandard/MqttServerFactory.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Server;
+using MQTTnet.Implementations;
+
+namespace MQTTnet
+{
+    public class MqttServerFactory
+    {
+        public IMqttServer CreateMqttServer(MqttServerOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            return new MqttServer(options, new List<IMqttServerAdapter> { new MqttServerAdapter() });
+        }
+    }
+}

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttServerAdapter.cs

@@ -0,0 +1,64 @@
+using System;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Serializer;
+using MQTTnet.Core.Server;
+using Windows.Networking.Sockets;
+
+namespace MQTTnet.Implementations
+{
+    public class MqttServerAdapter : IMqttServerAdapter, IDisposable
+    {
+        private StreamSocketListener _defaultEndpointSocket;
+        
+        private bool _isRunning;
+
+        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+
+        public void Start(MqttServerOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (_isRunning) throw new InvalidOperationException("Server is already started.");
+            _isRunning = true;
+
+            if (options.DefaultEndpointOptions.IsEnabled)
+            {
+                _defaultEndpointSocket = new StreamSocketListener();
+                _defaultEndpointSocket.BindServiceNameAsync(options.GetDefaultEndpointPort().ToString(), SocketProtectionLevel.PlainSocket).GetAwaiter().GetResult();
+                _defaultEndpointSocket.ConnectionReceived += AcceptDefaultEndpointConnectionsAsync;                
+            }
+
+            if (options.TlsEndpointOptions.IsEnabled)
+            {
+                throw new NotSupportedException("TLS servers are not supported for UWP apps.");
+            }
+        }
+
+        public void Stop()
+        {
+            _isRunning = false;
+
+            _defaultEndpointSocket?.Dispose();
+            _defaultEndpointSocket = null;
+        }
+
+        public void Dispose()
+        {
+            Stop();
+        }
+
+        private void AcceptDefaultEndpointConnectionsAsync(StreamSocketListener sender, StreamSocketListenerConnectionReceivedEventArgs args)
+        {
+            try
+            {
+                var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(args.Socket), new DefaultMqttV311PacketSerializer());
+                ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(args.Socket.Information.RemoteAddress.ToString(), clientAdapter));
+            }
+            catch (Exception exception)
+            {
+                MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at default endpoint.");
+            }
+        }
+    }
+}

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs

@@ -0,0 +1,120 @@
+using System;
+using System.Linq;
+using System.Net.Sockets;
+using System.Runtime.InteropServices.WindowsRuntime;
+using System.Threading.Tasks;
+using Windows.Networking;
+using Windows.Networking.Sockets;
+using Windows.Security.Cryptography.Certificates;
+using Windows.Storage.Streams;
+using MQTTnet.Core.Channel;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Exceptions;
+
+namespace MQTTnet.Implementations
+{
+    public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private readonly StreamSocket _socket;
+
+        public MqttTcpChannel()
+        {
+            _socket = new StreamSocket();
+        }
+
+        public MqttTcpChannel(StreamSocket socket)
+        {
+            _socket = socket ?? throw new ArgumentNullException(nameof(socket));
+        }
+
+        public async Task ConnectAsync(MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+            try
+            {
+                if (!options.TlsOptions.UseTls)
+                {
+                    await _socket.ConnectAsync(new HostName(options.Server), options.GetPort().ToString());
+                }
+                else
+                {
+                    _socket.Control.ClientCertificate = LoadCertificate(options);
+
+                    if (!options.TlsOptions.CheckCertificateRevocation)
+                    {
+                        _socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.IncompleteChain);
+                        _socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.RevocationInformationMissing);
+                    }
+
+                    await _socket.ConnectAsync(new HostName(options.Server), options.GetPort().ToString(), SocketProtectionLevel.Tls12);
+                }
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public Task DisconnectAsync()
+        {
+            try
+            {
+                _socket.Dispose();
+                return Task.FromResult(0);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public async Task WriteAsync(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+
+            try
+            {
+                await _socket.OutputStream.WriteAsync(buffer.AsBuffer());
+                await _socket.OutputStream.FlushAsync();
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public async Task ReadAsync(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+
+            try
+            {
+                await _socket.InputStream.ReadAsync(buffer.AsBuffer(), (uint)buffer.Length, InputStreamOptions.None);
+            }
+            catch (SocketException exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        public void Dispose()
+        {
+            _socket?.Dispose();
+        }
+
+        private static Certificate LoadCertificate(MqttClientOptions options)
+        {
+            if (options.TlsOptions.Certificates == null || !options.TlsOptions.Certificates.Any())
+            {
+                return null;
+            }
+
+            if (options.TlsOptions.Certificates.Count > 1)
+            {
+                throw new NotSupportedException("Only one client certificate is supported for UWP.");
+            }
+
+            return new Certificate(options.TlsOptions.Certificates.First().AsBuffer());
+        }
+    }
+}

Frameworks/MQTTnet.UniversalWindows/MQTTnet.UniversalWindows.csproj

@@ -11,11 +11,12 @@
     <AssemblyName>MQTTnet</AssemblyName>
     <DefaultLanguage>en-US</DefaultLanguage>
     <TargetPlatformIdentifier>UAP</TargetPlatformIdentifier>
-    <TargetPlatformVersion>10.0.14393.0</TargetPlatformVersion>
+    <TargetPlatformVersion>10.0.15063.0</TargetPlatformVersion>
     <TargetPlatformMinVersion>10.0.10240.0</TargetPlatformMinVersion>
     <MinimumVisualStudioVersion>14</MinimumVisualStudioVersion>
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <RuntimeIdentifiers>win10-arm;win10-arm-aot;win10-x86;win10-x86-aot;win10-x64;win10-x64-aot</RuntimeIdentifiers>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -26,6 +27,7 @@
     <DefineConstants>DEBUG;TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <NoWarn>CS1591</NoWarn>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -35,13 +37,14 @@
     <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <NoWarn>CS1591</NoWarn>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
     <PlatformTarget>x86</PlatformTarget>
     <DebugSymbols>true</DebugSymbols>
     <OutputPath>bin\x86\Debug\</OutputPath>
     <DefineConstants>DEBUG;TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
-    <NoWarn>;2008</NoWarn>
+    <NoWarn>;2008,CS1591</NoWarn>
     <DebugType>full</DebugType>
     <PlatformTarget>x86</PlatformTarget>
     <UseVSHostingProcess>false</UseVSHostingProcess>
@@ -52,18 +55,19 @@
     <OutputPath>bin\x86\Release\</OutputPath>
     <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
     <Optimize>true</Optimize>
-    <NoWarn>;2008</NoWarn>
+    <NoWarn>;2008,CS1591</NoWarn>
     <DebugType>pdbonly</DebugType>
     <PlatformTarget>x86</PlatformTarget>
     <UseVSHostingProcess>false</UseVSHostingProcess>
     <ErrorReport>prompt</ErrorReport>
+    <DocumentationFile>bin\x86\Release\MQTTnet.XML</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|ARM'">
     <PlatformTarget>ARM</PlatformTarget>
     <DebugSymbols>true</DebugSymbols>
     <OutputPath>bin\ARM\Debug\</OutputPath>
     <DefineConstants>DEBUG;TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
-    <NoWarn>;2008</NoWarn>
+    <NoWarn>;2008,CS1591</NoWarn>
     <DebugType>full</DebugType>
     <PlatformTarget>ARM</PlatformTarget>
     <UseVSHostingProcess>false</UseVSHostingProcess>
@@ -74,18 +78,19 @@
     <OutputPath>bin\ARM\Release\</OutputPath>
     <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
     <Optimize>true</Optimize>
-    <NoWarn>;2008</NoWarn>
+    <NoWarn>;2008,CS1591</NoWarn>
     <DebugType>pdbonly</DebugType>
     <PlatformTarget>ARM</PlatformTarget>
     <UseVSHostingProcess>false</UseVSHostingProcess>
     <ErrorReport>prompt</ErrorReport>
+    <DocumentationFile>bin\ARM\Release\MQTTnet.XML</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
     <PlatformTarget>x64</PlatformTarget>
     <DebugSymbols>true</DebugSymbols>
     <OutputPath>bin\x64\Debug\</OutputPath>
     <DefineConstants>DEBUG;TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
-    <NoWarn>;2008</NoWarn>
+    <NoWarn>;2008,CS1591</NoWarn>
     <DebugType>full</DebugType>
     <PlatformTarget>x64</PlatformTarget>
     <UseVSHostingProcess>false</UseVSHostingProcess>
@@ -96,33 +101,86 @@
     <OutputPath>bin\x64\Release\</OutputPath>
     <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
     <Optimize>true</Optimize>
-    <NoWarn>;2008</NoWarn>
+    <NoWarn>;2008,CS1591</NoWarn>
     <DebugType>pdbonly</DebugType>
     <PlatformTarget>x64</PlatformTarget>
     <UseVSHostingProcess>false</UseVSHostingProcess>
     <ErrorReport>prompt</ErrorReport>
+    <GenerateLibraryLayout>false</GenerateLibraryLayout>
+    <DocumentationFile>bin\x64\Release\MQTTnet.XML</DocumentationFile>
   </PropertyGroup>
-  <ItemGroup>
-    <!-- A reference to the entire .Net Framework and Windows SDK are automatically included -->
-    <None Include="project.json" />
-  </ItemGroup>
   <ItemGroup>
     <Compile Include="MqttClientFactory.cs" />
-    <Compile Include="MqttServerAdapter.cs" />
+    <Compile Include="Implementations\MqttServerAdapter.cs" />
     <Compile Include="MqttServerFactory.cs" />
-    <Compile Include="MqttTcpChannel.cs" />
+    <Compile Include="Implementations\MqttTcpChannel.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <EmbeddedResource Include="Properties\MQTTnet.Universal.rd.xml" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj">
-      <Project>{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}</Project>
+      <Project>{2ecb99e4-72d0-4c23-99ba-93d511d3967d}</Project>
       <Name>MQTTnet.Core</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
+      <Version>5.3.3</Version>
+    </PackageReference>
+  </ItemGroup>
   <PropertyGroup Condition=" '$(VisualStudioVersion)' == '' or '$(VisualStudioVersion)' &lt; '14.0' ">
     <VisualStudioVersion>14.0</VisualStudioVersion>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|AnyCPU'">
+    <OutputPath>bin\Any CPU\</OutputPath>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <Optimize>true</Optimize>
+    <NoStdLib>true</NoStdLib>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <UseVSHostingProcess>false</UseVSHostingProcess>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x86'">
+    <OutputPath>bin\x86\Any CPU\</OutputPath>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DocumentationFile>bin\x86\Release\MQTTnet.XML</DocumentationFile>
+    <Optimize>true</Optimize>
+    <NoWarn>;2008</NoWarn>
+    <NoStdLib>true</NoStdLib>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x86</PlatformTarget>
+    <UseVSHostingProcess>false</UseVSHostingProcess>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|ARM'">
+    <OutputPath>bin\ARM\Any CPU\</OutputPath>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DocumentationFile>bin\ARM\Release\MQTTnet.XML</DocumentationFile>
+    <Optimize>true</Optimize>
+    <NoWarn>;2008</NoWarn>
+    <NoStdLib>true</NoStdLib>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>ARM</PlatformTarget>
+    <UseVSHostingProcess>false</UseVSHostingProcess>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x64'">
+    <OutputPath>bin\x64\Any CPU\</OutputPath>
+    <DefineConstants>TRACE;NETFX_CORE;WINDOWS_UWP</DefineConstants>
+    <DocumentationFile>bin\x64\Release\MQTTnet.XML</DocumentationFile>
+    <Optimize>true</Optimize>
+    <NoWarn>;2008</NoWarn>
+    <NoStdLib>true</NoStdLib>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <UseVSHostingProcess>false</UseVSHostingProcess>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
   <Import Project="$(MSBuildExtensionsPath)\Microsoft\WindowsXaml\v$(VisualStudioVersion)\Microsoft.Windows.UI.Xaml.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

Frameworks/MQTTnet.UniversalWindows/MqttClientFactory.cs

@@ -2,16 +2,17 @@
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Serializer;
+using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
     public class MqttClientFactory
     {
-        public MqttClient CreateMqttClient(MqttClientOptions options)
+        public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
             return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new DefaultMqttV311PacketSerializer()));
         }
     }
-}
+}

Frameworks/MQTTnet.UniversalWindows/MqttServerAdapter.cs

@@ -1,54 +0,0 @@
-using System;
-using System.Threading;
-using Windows.Networking.Sockets;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Serializer;
-using MQTTnet.Core.Server;
-
-namespace MQTTnet
-{
-    public sealed class MqttServerAdapter : IMqttServerAdapter, IDisposable
-    {
-        private CancellationTokenSource _cancellationTokenSource;
-        private StreamSocketListener _socket;
-
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
-
-        public void Start(MqttServerOptions options)
-        {
-            if (_socket != null) throw new InvalidOperationException("Server is already started.");
-
-            _cancellationTokenSource = new CancellationTokenSource();
-
-            _socket = new StreamSocketListener();
-            _socket.BindServiceNameAsync(options.Port.ToString()).AsTask().Wait();
-            _socket.ConnectionReceived += ConnectionReceived;
-        }
-
-        private void ConnectionReceived(StreamSocketListener sender, StreamSocketListenerConnectionReceivedEventArgs args)
-        {
-            var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(args.Socket), new DefaultMqttV311PacketSerializer());
-
-            var identifier = $"{args.Socket.Information.RemoteAddress}:{args.Socket.Information.RemotePort}";
-            ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(identifier, clientAdapter));
-        }
-
-        public void Stop()
-        {
-            _cancellationTokenSource?.Dispose();
-
-            if (_socket != null)
-            {
-                _socket.ConnectionReceived -= ConnectionReceived;
-            }
-
-            _socket?.Dispose();
-            _socket = null;
-        }
-
-        public void Dispose()
-        {
-            Stop();
-        }
-    }
-}

Frameworks/MQTTnet.UniversalWindows/MqttServerFactory.cs

@@ -1,15 +1,18 @@
 using System;
+using System.Collections.Generic;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Server;
+using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
     public class MqttServerFactory
     {
-        public MqttServer CreateMqttServer(MqttServerOptions options)
+        public IMqttServer CreateMqttServer(MqttServerOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
-            return new MqttServer(options, new MqttServerAdapter());
+            return new MqttServer(options, new List<IMqttServerAdapter> { new MqttServerAdapter() });
         }
     }
 }

Frameworks/MQTTnet.UniversalWindows/MqttTcpChannel.cs

@@ -1,62 +0,0 @@
-using System;
-using System.Runtime.InteropServices.WindowsRuntime;
-using System.Threading.Tasks;
-using Windows.Networking;
-using Windows.Networking.Sockets;
-using Windows.Storage.Streams;
-using MQTTnet.Core.Channel;
-using MQTTnet.Core.Client;
-using Buffer = Windows.Storage.Streams.Buffer;
-
-namespace MQTTnet
-{
-    public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
-    {
-        private readonly StreamSocket _socket;
-
-        public MqttTcpChannel()
-        {
-            _socket = new StreamSocket();
-        }
-
-        public MqttTcpChannel(StreamSocket socket)
-        {
-            _socket = socket ?? throw new ArgumentNullException(nameof(socket));
-        }
-
-        public async Task ConnectAsync(MqttClientOptions options)
-        {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-
-            await _socket.ConnectAsync(new HostName(options.Server), options.Port.ToString());
-        }
-
-        public async Task DisconnectAsync()
-        {
-            await _socket.CancelIOAsync();
-            _socket.Dispose();
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            await _socket.OutputStream.WriteAsync(buffer.AsBuffer());
-            await _socket.OutputStream.FlushAsync();
-        }
-
-        public async Task ReadAsync(byte[] buffer)
-        {
-            var buffer2 = new Buffer((uint)buffer.Length);
-            await _socket.InputStream.ReadAsync(buffer2, (uint)buffer.Length, InputStreamOptions.None);
-
-            var array2 = buffer2.ToArray();
-            Array.Copy(array2, buffer, array2.Length);
-        }
-
-        public void Dispose()
-        {
-            _socket?.Dispose();
-        }
-    }
-}

Frameworks/MQTTnet.UniversalWindows/Properties/AssemblyInfo.cs

@@ -10,5 +10,5 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
 [assembly: ComVisible(false)]
-[assembly: AssemblyVersion("2.1.0.4")]
-[assembly: AssemblyFileVersion("2.1.0.4")]
+[assembly: AssemblyVersion("2.1.4.0")]
+[assembly: AssemblyFileVersion("2.1.4.0")]

Frameworks/MQTTnet.UniversalWindows/Properties/MQTTnet.Universal.rd.xml

@@ -1,33 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!--
-    This file contains Runtime Directives, specifications about types your application accesses
-    through reflection and other dynamic code patterns. Runtime Directives are used to control the
-    .NET Native optimizer and ensure that it does not remove code accessed by your library. If your
-    library does not do any reflection, then you generally do not need to edit this file. However,
-    if your library reflects over types, especially types passed to it or derived from its types,
-    then you should write Runtime Directives.
-
-    The most common use of reflection in libraries is to discover information about types passed
-    to the library. Runtime Directives have three ways to express requirements on types passed to
-    your library.
-
-    1.  Parameter, GenericParameter, TypeParameter, TypeEnumerableParameter
-        Use these directives to reflect over types passed as a parameter.
-
-    2.  SubTypes
-        Use a SubTypes directive to reflect over types derived from another type.
-
-    3.  AttributeImplies
-        Use an AttributeImplies directive to indicate that your library needs to reflect over
-        types or methods decorated with an attribute.
-
-    For more information on writing Runtime Directives for libraries, please visit
-    http://go.microsoft.com/fwlink/?LinkID=391919
--->
 <Directives xmlns="http://schemas.microsoft.com/netfx/2013/01/metadata">
   <Library Name="MQTTnet.Universal">
-
-  	<!-- add directives for your library here -->
-
   </Library>
 </Directives>

Frameworks/MQTTnet.UniversalWindows/project.json

@@ -1,16 +0,0 @@
-{
-  "dependencies": {
-    "Microsoft.NETCore.UniversalWindowsPlatform": "5.1.0"
-  },
-  "frameworks": {
-    "uap10.0": {}
-  },
-  "runtimes": {
-    "win10-arm": {},
-    "win10-arm-aot": {},
-    "win10-x86": {},
-    "win10-x86-aot": {},
-    "win10-x64": {},
-    "win10-x64-aot": {}
-  }
-}

MQTTnet.Core/Client/IMqttClient.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Client
+{
+    public interface IMqttClient
+    {
+        bool IsConnected { get; }
+
+        event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
+        event EventHandler Connected;
+        event EventHandler Disconnected;
+
+        Task ConnectAsync(MqttApplicationMessage willApplicationMessage = null);
+        Task DisconnectAsync();
+        Task PublishAsync(MqttApplicationMessage applicationMessage);
+        Task<IList<MqttSubscribeResult>> SubscribeAsync(IList<TopicFilter> topicFilters);
+        Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters);
+        Task Unsubscribe(IList<string> topicFilters);
+        Task Unsubscribe(params string[] topicFilters);
+    }
+}

MQTTnet.Core/Client/MqttApplicationMessageReceivedEventArgs.cs

@@ -1,8 +1,8 @@
 using System;
 
-namespace MQTTnet.Core
+namespace MQTTnet.Core.Client
 {
-    public class MqttApplicationMessageReceivedEventArgs : EventArgs
+    public sealed class MqttApplicationMessageReceivedEventArgs : EventArgs
     {
         public MqttApplicationMessageReceivedEventArgs(MqttApplicationMessage applicationMessage)
         {

MQTTnet.Core/Client/MqttClient.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -13,10 +12,9 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Client
 {
-    public class MqttClient
+    public class MqttClient : IMqttClient
     {
-        private readonly ConcurrentDictionary<ushort, MqttPublishPacket> _pendingExactlyOncePublishPackets = new ConcurrentDictionary<ushort, MqttPublishPacket>();
-        private readonly HashSet<ushort> _processedPublishPackets = new HashSet<ushort>();
+        private readonly HashSet<ushort> _unacknowledgedPublishPackets = new HashSet<ushort>();
 
         private readonly MqttPacketDispatcher _packetDispatcher = new MqttPacketDispatcher();
         private readonly MqttClientOptions _options;
@@ -53,6 +51,7 @@ namespace MQTTnet.Core.Client
                 ClientId = _options.ClientId,
                 Username = _options.UserName,
                 Password = _options.Password,
+                CleanSession = _options.CleanSession,
                 KeepAlivePeriod = (ushort)_options.KeepAlivePeriod.TotalSeconds,
                 WillMessage = willApplicationMessage
             };
@@ -62,21 +61,25 @@ namespace MQTTnet.Core.Client
 
             _cancellationTokenSource = new CancellationTokenSource();
             _latestPacketIdentifier = 0;
-            _processedPublishPackets.Clear();
             _packetDispatcher.Reset();
             IsConnected = true;
 
-            Task.Run(async () => await ReceivePackets(_cancellationTokenSource.Token), _cancellationTokenSource.Token).Forget();
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            Task.Run(() => ReceivePackets(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
 
             var response = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket);
             if (response.ConnectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
             {
+                await DisconnectAsync();
                 throw new MqttConnectingFailedException(response.ConnectReturnCode);
             }
 
             if (_options.KeepAlivePeriod != TimeSpan.Zero)
             {
-                Task.Run(async () => await SendKeepAliveMessagesAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token).Forget();
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+                Task.Run(() => SendKeepAliveMessagesAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
             }
 
             Connected?.Invoke(this, EventArgs.Empty);
@@ -88,17 +91,18 @@ namespace MQTTnet.Core.Client
             await DisconnectInternalAsync();
         }
 
-        public async Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters)
+        public Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters)
         {
             if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
 
-            return await SubscribeAsync(topicFilters.ToList());
+            return SubscribeAsync(topicFilters.ToList());
         }
 
         public async Task<IList<MqttSubscribeResult>> SubscribeAsync(IList<TopicFilter> topicFilters)
         {
             if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
             if (!topicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.8.3-3].");
+
             ThrowIfNotConnected();
 
             var subscribePacket = new MqttSubscribePacket
@@ -114,20 +118,14 @@ namespace MQTTnet.Core.Client
                 throw new MqttProtocolViolationException("The return codes are not matching the topic filters [MQTT-3.9.3-1].");
             }
 
-            var result = new List<MqttSubscribeResult>();
-            for (var i = 0; i < topicFilters.Count; i++)
-            {
-                result.Add(new MqttSubscribeResult(topicFilters[i], response.SubscribeReturnCodes[i]));
-            }
-
-            return result;
+            return topicFilters.Select((t, i) => new MqttSubscribeResult(t, response.SubscribeReturnCodes[i])).ToList();
         }
 
-        public async Task Unsubscribe(params string[] topicFilters)
+        public Task Unsubscribe(params string[] topicFilters)
         {
             if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
 
-            await Unsubscribe(topicFilters.ToList());
+            return Unsubscribe(topicFilters.ToList());
         }
 
         public async Task Unsubscribe(IList<string> topicFilters)
@@ -154,6 +152,7 @@ namespace MQTTnet.Core.Client
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
             {
+                // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
                 await SendAsync(publishPacket);
             }
             else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
@@ -164,8 +163,8 @@ namespace MQTTnet.Core.Client
             else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
             {
                 publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket);
-                await SendAsync(publishPacket.CreateResponse<MqttPubCompPacket>());
+                var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket);
+                await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>());
             }
         }
 
@@ -185,40 +184,37 @@ namespace MQTTnet.Core.Client
             }
             finally
             {
-                _cancellationTokenSource?.Cancel();
+                _cancellationTokenSource?.Cancel(false);
+                _cancellationTokenSource?.Dispose();
+                _cancellationTokenSource = null;
+
                 IsConnected = false;
                 Disconnected?.Invoke(this, EventArgs.Empty);
             }
         }
 
-        private async void ProcessReceivedPacket(MqttBasePacket mqttPacket)
+        private Task ProcessReceivedPacketAsync(MqttBasePacket mqttPacket)
         {
             try
             {
                 if (mqttPacket is MqttPingReqPacket)
                 {
-                    await SendAsync(new MqttPingRespPacket());
-                    return;
+                    return SendAsync(new MqttPingRespPacket());
                 }
 
                 if (mqttPacket is MqttDisconnectPacket)
                 {
-                    await DisconnectAsync();
-                    return;
+                    return DisconnectAsync();
                 }
 
-                var publishPacket = mqttPacket as MqttPublishPacket;
-                if (publishPacket != null)
+                if (mqttPacket is MqttPublishPacket publishPacket)
                 {
-                    await ProcessReceivedPublishPacket(publishPacket);
-                    return;
+                    return ProcessReceivedPublishPacket(publishPacket);
                 }
 
-                var pubRelPacket = mqttPacket as MqttPubRelPacket;
-                if (pubRelPacket != null)
+                if (mqttPacket is MqttPubRelPacket pubRelPacket)
                 {
-                    await ProcessReceivedPubRelPacket(pubRelPacket);
-                    return;
+                    return ProcessReceivedPubRelPacket(pubRelPacket);
                 }
 
                 _packetDispatcher.Dispatch(mqttPacket);
@@ -227,67 +223,71 @@ namespace MQTTnet.Core.Client
             {
                 MqttTrace.Error(nameof(MqttClient), exception, "Error while processing received packet.");
             }
+
+            return Task.FromResult(0);
         }
 
         private void FireApplicationMessageReceivedEvent(MqttPublishPacket publishPacket)
         {
-            if (publishPacket.QualityOfServiceLevel != MqttQualityOfServiceLevel.AtMostOnce)
+            var applicationMessage = publishPacket.ToApplicationMessage();
+
+            try
             {
-                _processedPublishPackets.Add(publishPacket.PacketIdentifier);
+                ApplicationMessageReceived?.Invoke(this, new MqttApplicationMessageReceivedEventArgs(applicationMessage));
+            }
+            catch (Exception exception)
+            {
+                MqttTrace.Error(nameof(MqttClient), exception, "Unhandled exception while handling application message.");    
             }
-
-            var applicationMessage = new MqttApplicationMessage(
-                publishPacket.Topic,
-                publishPacket.Payload,
-                publishPacket.QualityOfServiceLevel,
-                publishPacket.Retain
-            );
-
-            ApplicationMessageReceived?.Invoke(this, new MqttApplicationMessageReceivedEventArgs(applicationMessage));
         }
 
-        private async Task ProcessReceivedPublishPacket(MqttPublishPacket publishPacket)
+        private Task ProcessReceivedPublishPacket(MqttPublishPacket publishPacket)
         {
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
+                return Task.FromResult(0);
             }
-            else
+
+            if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
-                if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
-                {
-                    FireApplicationMessageReceivedEvent(publishPacket);
-                    await SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
-                }
-                else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
-                {
-                    _pendingExactlyOncePublishPackets[publishPacket.PacketIdentifier] = publishPacket;
-                    await SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
-                }
+                FireApplicationMessageReceivedEvent(publishPacket);
+                return SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
             }
+
+            if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
+            {
+                // QoS 2 is implement as method "B" [4.3.3 QoS 2: Exactly once delivery]
+                lock (_unacknowledgedPublishPackets)
+                {
+                    _unacknowledgedPublishPackets.Add(publishPacket.PacketIdentifier);
+                }
+
+                FireApplicationMessageReceivedEvent(publishPacket);
+                return SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+            }
+
+            throw new InvalidOperationException();
         }
 
         private async Task ProcessReceivedPubRelPacket(MqttPubRelPacket pubRelPacket)
         {
-            MqttPublishPacket originalPublishPacket;
-            if (!_pendingExactlyOncePublishPackets.TryRemove(pubRelPacket.PacketIdentifier, out originalPublishPacket))
+            lock (_unacknowledgedPublishPackets)
             {
-                throw new MqttCommunicationException();
+                _unacknowledgedPublishPackets.Remove(pubRelPacket.PacketIdentifier);
             }
-
-            await SendAsync(originalPublishPacket.CreateResponse<MqttPubCompPacket>());
-
-            FireApplicationMessageReceivedEvent(originalPublishPacket);
+            
+            await SendAsync(pubRelPacket.CreateResponse<MqttPubCompPacket>());
         }
 
-        private async Task SendAsync(MqttBasePacket packet)
+        private Task SendAsync(MqttBasePacket packet)
         {
-            await _adapter.SendPacketAsync(packet, _options.DefaultCommunicationTimeout);
+            return _adapter.SendPacketAsync(packet, _options.DefaultCommunicationTimeout);
         }
 
         private async Task<TResponsePacket> SendAndReceiveAsync<TResponsePacket>(MqttBasePacket requestPacket) where TResponsePacket : MqttBasePacket
         {
-            Func<MqttBasePacket, bool> responsePacketSelector = p =>
+            bool ResponsePacketSelector(MqttBasePacket p)
             {
                 var p1 = p as TResponsePacket;
                 if (p1 == null)
@@ -295,8 +295,8 @@ namespace MQTTnet.Core.Client
                     return false;
                 }
 
-                var pi1 = requestPacket as IPacketWithIdentifier;
-                var pi2 = p as IPacketWithIdentifier;
+                var pi1 = requestPacket as IMqttPacketWithIdentifier;
+                var pi2 = p as IMqttPacketWithIdentifier;
 
                 if (pi1 != null && pi2 != null)
                 {
@@ -307,10 +307,10 @@ namespace MQTTnet.Core.Client
                 }
 
                 return true;
-            };
+            }
 
             await _adapter.SendPacketAsync(requestPacket, _options.DefaultCommunicationTimeout);
-            return (TResponsePacket)await _packetDispatcher.WaitForPacketAsync(responsePacketSelector, _options.DefaultCommunicationTimeout);
+            return (TResponsePacket)await _packetDispatcher.WaitForPacketAsync(ResponsePacketSelector, _options.DefaultCommunicationTimeout);
         }
 
         private ushort GetNewPacketIdentifier()
@@ -330,8 +330,9 @@ namespace MQTTnet.Core.Client
                     await SendAndReceiveAsync<MqttPingRespPacket>(new MqttPingReqPacket());
                 }
             }
-            catch (MqttCommunicationException)
+            catch (MqttCommunicationException exception)
             {
+                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication error while receiving packets.");
             }
             catch (Exception exception)
             {
@@ -354,11 +355,14 @@ namespace MQTTnet.Core.Client
                     var mqttPacket = await _adapter.ReceivePacketAsync(TimeSpan.Zero);
                     MqttTrace.Information(nameof(MqttClient), $"Received <<< {mqttPacket}");
 
-                    Task.Run(() => ProcessReceivedPacket(mqttPacket), cancellationToken).Forget();
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+                    Task.Run(() => ProcessReceivedPacketAsync(mqttPacket), cancellationToken);
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
                 }
             }
-            catch (MqttCommunicationException)
+            catch (MqttCommunicationException exception)
             {
+                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication error while receiving packets.");
             }
             catch (Exception exception)
             {

MQTTnet.Core/Client/MqttClientOptions.cs

@@ -2,11 +2,13 @@
 
 namespace MQTTnet.Core.Client
 {
-    public class MqttClientOptions
+    public sealed class MqttClientOptions
     {
         public string Server { get; set; }
 
-        public int Port { get; set; } = 1883;
+        public int? Port { get; set; }
+        
+        public MqttClientTlsOptions TlsOptions { get; } = new MqttClientTlsOptions();
 
         public string UserName { get; set; }
 
@@ -14,6 +16,8 @@ namespace MQTTnet.Core.Client
 
         public string ClientId { get; set; } = Guid.NewGuid().ToString().Replace("-", string.Empty);
 
+        public bool CleanSession { get; set; } = true;
+
         public TimeSpan KeepAlivePeriod { get; set; } = TimeSpan.FromSeconds(5);
 
         public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(10);

MQTTnet.Core/Client/MqttClientOptionsExtensions.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace MQTTnet.Core.Client
+{
+    public static class MqttClientOptionsExtensions
+    {
+        public static int GetPort(this MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (options.Port.HasValue)
+            {
+                return options.Port.Value;
+            }
+
+            return !options.TlsOptions.UseTls ? 1883 : 8883;
+        }
+    }
+}

MQTTnet.Core/Client/MqttClientTlsOptions.cs

@@ -0,0 +1,13 @@
+using System.Collections.Generic;
+
+namespace MQTTnet.Core.Client
+{
+    public sealed class MqttClientTlsOptions
+    {
+        public bool UseTls { get; set; }
+
+        public bool CheckCertificateRevocation { get; set; }
+
+        public List<byte[]> Certificates { get; set; }
+    }
+}

MQTTnet.Core/Diagnostics/MqttTraceMessagePublishedEventArgs.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Diagnostics
 {
-    public class MqttTraceMessagePublishedEventArgs : EventArgs
+    public sealed class MqttTraceMessagePublishedEventArgs : EventArgs
     {
         public MqttTraceMessagePublishedEventArgs(int threadId, string source, MqttTraceLevel level, string message, Exception exception)
         {

MQTTnet.Core/Exceptions/MqttCommunicationTimedOutException.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Exceptions
 {
-    public class MqttCommunicationTimedOutException : MqttCommunicationException
+    public sealed class MqttCommunicationTimedOutException : MqttCommunicationException
     {
     }
 }

MQTTnet.Core/Exceptions/MqttProtocolViolationException.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Exceptions
 {
-    public class MqttProtocolViolationException : Exception
+    public sealed class MqttProtocolViolationException : Exception
     {
         public MqttProtocolViolationException(string message) 
             : base(message)

MQTTnet.Core/Internal/AsyncAutoResetEvent.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Core.Internal
+{
+    public sealed class AsyncGate
+    {
+        private readonly Queue<TaskCompletionSource<bool>> _waitingTasks = new Queue<TaskCompletionSource<bool>>();
+
+        public Task WaitOneAsync()
+        {
+            var tcs = new TaskCompletionSource<bool>();
+            lock (_waitingTasks)
+            {
+                _waitingTasks.Enqueue(tcs);
+            }
+
+            return tcs.Task;
+        }
+
+        public void Set()
+        {
+            lock (_waitingTasks)
+            {
+                if (_waitingTasks.Count > 0)
+                {
+                    _waitingTasks.Dequeue().SetResult(true);
+                }
+            }
+        }
+    }
+}

MQTTnet.Core/Internal/MqttApplicationMessageExtensions.cs

@@ -4,6 +4,16 @@ namespace MQTTnet.Core.Internal
 {
     internal static class MqttApplicationMessageExtensions
     {
+        public static MqttApplicationMessage ToApplicationMessage(this MqttPublishPacket publishPacket)
+        {
+            return new MqttApplicationMessage(
+                publishPacket.Topic,
+                publishPacket.Payload,
+                publishPacket.QualityOfServiceLevel,
+                publishPacket.Retain
+            );
+        }
+
         public static MqttPublishPacket ToPublishPacket(this MqttApplicationMessage applicationMessage)
         {
             if (applicationMessage == null)

MQTTnet.Core/Internal/TaskExtensions.cs

@@ -1,11 +0,0 @@
-using System.Threading.Tasks;
-
-namespace MQTTnet.Core.Internal
-{
-    internal static class TaskExtensions
-    {
-        public static void Forget(this Task task)
-        {
-        }
-    }
-}

MQTTnet.Core/MQTTnet.Core.csproj

@@ -1,107 +1,34 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+<Project Sdk="Microsoft.NET.Sdk">
+
   <PropertyGroup>
-    <MinimumVisualStudioVersion>10.0</MinimumVisualStudioVersion>
-    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
-    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
-    <ProjectGuid>{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}</ProjectGuid>
-    <OutputType>Library</OutputType>
-    <AppDesignerFolder>Properties</AppDesignerFolder>
-    <RootNamespace>MQTTnet.Core</RootNamespace>
+    <TargetFramework>netstandard1.1</TargetFramework>
     <AssemblyName>MQTTnet.Core</AssemblyName>
-    <DefaultLanguage>en-US</DefaultLanguage>
-    <FileAlignment>512</FileAlignment>
-    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
-    <TargetFrameworkProfile>Profile111</TargetFrameworkProfile>
-    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <RootNamespace>MQTTnet.Core</RootNamespace>
+    <GeneratePackageOnBuild>False</GeneratePackageOnBuild>
+    <Description></Description>
+    <Product></Product>
+    <Company></Company>
+    <Authors></Authors>
+    <Version>0.0.0.0</Version>
+    <PackageId></PackageId>
+    <Copyright></Copyright>
+    <PackageProjectUrl></PackageProjectUrl>
+    <PackageIconUrl></PackageIconUrl>
+    <RepositoryUrl></RepositoryUrl>
+    <PackageTags></PackageTags>
+    <FileVersion>2.1.4.0</FileVersion>
+    <AssemblyVersion>2.1.4.0</AssemblyVersion>
+    <PackageLicenseUrl></PackageLicenseUrl>
   </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
-    <DebugSymbols>true</DebugSymbols>
-    <DebugType>full</DebugType>
-    <Optimize>false</Optimize>
-    <OutputPath>bin\Debug\</OutputPath>
-    <DefineConstants>DEBUG;TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
-    <DebugType>pdbonly</DebugType>
-    <Optimize>true</Optimize>
-    <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-  </PropertyGroup>
-  <ItemGroup>
-    <!-- A reference to the entire .NET Framework is automatically included -->
-  </ItemGroup>
-  <ItemGroup>
-    <Compile Include="Adapter\IMqttCommunicationAdapter.cs" />
-    <Compile Include="Adapter\IMqttServerAdapter.cs" />
-    <Compile Include="Adapter\MqttClientConnectedEventArgs.cs" />
-    <Compile Include="Adapter\MqttConnectingFailedException.cs" />
-    <Compile Include="Adapter\MqttChannelCommunicationAdapter.cs" />
-    <Compile Include="Channel\IMqttCommunicationChannel.cs" />
-    <Compile Include="Client\MqttPacketDispatcher.cs" />
-    <Compile Include="Client\MqttSubscribeResult.cs" />
-    <Compile Include="Client\MqttPacketAwaiter.cs" />
-    <Compile Include="Diagnostics\MqttTrace.cs" />
-    <Compile Include="Diagnostics\MqttTraceLevel.cs" />
-    <Compile Include="Diagnostics\MqttTraceMessagePublishedEventArgs.cs" />
-    <Compile Include="Exceptions\MqttCommunicationException.cs" />
-    <Compile Include="Exceptions\MqttCommunicationTimedOutException.cs" />
-    <Compile Include="Exceptions\MqttProtocolViolationException.cs" />
-    <Compile Include="Internal\MqttApplicationMessageExtensions.cs" />
-    <Compile Include="MqttApplicationMessageReceivedEventArgs.cs" />
-    <Compile Include="Packets\IPacketWithPacketIdentifier.cs" />
-    <Compile Include="Packets\MqttConnAckPacket.cs" />
-    <Compile Include="Packets\MqttBasePacket.cs" />
-    <Compile Include="Packets\MqttConnectPacket.cs" />
-    <Compile Include="Packets\MqttDisconnectPacket.cs" />
-    <Compile Include="MqttApplicationMessage.cs" />
-    <Compile Include="Client\MqttClient.cs" />
-    <Compile Include="Client\MqttClientOptions.cs" />
-    <Compile Include="Packets\MqttPingReqPacket.cs" />
-    <Compile Include="Packets\MqttPubCompPacket.cs" />
-    <Compile Include="Packets\MqttBasePublishPacket.cs" />
-    <Compile Include="Packets\MqttUnsubAckPacket.cs" />
-    <Compile Include="Packets\MqttSubAckPacket.cs" />
-    <Compile Include="Packets\MqttPubRelPacket.cs" />
-    <Compile Include="Packets\MqttPingRespPacket.cs" />
-    <Compile Include="Packets\MqttPubAckPacket.cs" />
-    <Compile Include="Packets\MqttPublishPacket.cs" />
-    <Compile Include="Packets\MqttPubRecPacket.cs" />
-    <Compile Include="Packets\MqttUnsubscribe.cs" />
-    <Compile Include="Packets\MqttSubscribePacket.cs" />
-    <Compile Include="Packets\TopicFilter.cs" />
-    <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="Protocol\MqttConnectReturnCode.cs" />
-    <Compile Include="Protocol\MqttControlPacketType.cs" />
-    <Compile Include="Protocol\MqttQualityOfServiceLevel.cs" />
-    <Compile Include="Protocol\MqttSubscribeReturnCode.cs" />
-    <Compile Include="Serializer\ByteReader.cs" />
-    <Compile Include="Serializer\ByteWriter.cs" />
-    <Compile Include="Serializer\DefaultMqttV311PacketSerializer.cs" />
-    <Compile Include="Serializer\IMqttPacketSerializer.cs" />
-    <Compile Include="Serializer\MqttPacketReader.cs" />
-    <Compile Include="Serializer\MqttPacketWriter.cs" />
-    <Compile Include="Server\MqttClientSession.cs" />
-    <Compile Include="Server\MqttClientSessionManager.cs" />
-    <Compile Include="Server\MqttOutgoingPublicationsManager.cs" />
-    <Compile Include="Server\MqttServer.cs" />
-    <Compile Include="Server\MqttServerOptions.cs" />
-    <Compile Include="Server\MqttClientPublishPacketContext.cs" />
-    <Compile Include="Server\MqttTopicFilterComparer.cs" />
-    <Compile Include="Server\MqttClientSubscriptionsManager.cs" />
-    <Compile Include="Internal\TaskExtensions.cs" />
-  </ItemGroup>
-  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
-  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
-       Other similar extension points exist, see Microsoft.Common.targets.
-  <Target Name="BeforeBuild">
-  </Target>
-  <Target Name="AfterBuild">
-  </Target>
-  -->
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Any CPU|AnyCPU'" />
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Any CPU|x64'" />
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x86'" />
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x86'" />
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Any CPU|x86'" />
+
 </Project>

MQTTnet.Core/MqttApplicationMessage.cs

@@ -3,7 +3,7 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core
 {
-    public class MqttApplicationMessage
+    public sealed class MqttApplicationMessage
     {
         public MqttApplicationMessage(string topic, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, bool retain)
         {

MQTTnet.Core/Packets/IMqttPacketWithIdentifier.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public interface IPacketWithIdentifier
+    public interface IMqttPacketWithIdentifier
     {
         ushort PacketIdentifier { get; set; }
     }

MQTTnet.Core/Packets/MqttBasePacket.cs

@@ -1,25 +1,6 @@
-using System;
-
-namespace MQTTnet.Core.Packets
+namespace MQTTnet.Core.Packets
 {
     public abstract class MqttBasePacket
     {
-        public TResponsePacket CreateResponse<TResponsePacket>()
-        {
-            var responsePacket = Activator.CreateInstance<TResponsePacket>();
-            var responsePacketWithIdentifier = responsePacket as IPacketWithIdentifier;
-            if (responsePacketWithIdentifier != null)
-            {
-                var requestPacketWithIdentifier = this as IPacketWithIdentifier;
-                if (requestPacketWithIdentifier == null)
-                {
-                    throw new InvalidOperationException("Response packet has PacketIdentifier but request packet does not.");
-                }
-
-                responsePacketWithIdentifier.PacketIdentifier = requestPacketWithIdentifier.PacketIdentifier;
-            }
-
-            return responsePacket;
-        }
     }
 }

MQTTnet.Core/Packets/MqttBasePublishPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttBasePublishPacket : MqttBasePacket, IPacketWithIdentifier
+    public class MqttBasePublishPacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
     }

MQTTnet.Core/Packets/MqttConnAckPacket.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Packets
 {
-    public class MqttConnAckPacket : MqttBasePacket
+    public sealed class MqttConnAckPacket : MqttBasePacket
     {
         public bool IsSessionPresent { get; set; }
 

MQTTnet.Core/Packets/MqttConnectPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttConnectPacket: MqttBasePacket
+    public sealed class MqttConnectPacket: MqttBasePacket
     {
         public string ClientId { get; set; }
 

MQTTnet.Core/Packets/MqttDisconnectPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttDisconnectPacket : MqttBasePacket
+    public sealed class MqttDisconnectPacket : MqttBasePacket
     {
     }
 }

MQTTnet.Core/Packets/MqttPacketExtensions.cs

@@ -0,0 +1,27 @@
+using System;
+
+namespace MQTTnet.Core.Packets
+{
+    public static class MqttPacketExtensions
+    {
+        public static TResponsePacket CreateResponse<TResponsePacket>(this MqttBasePacket packet)
+        {
+            if (packet == null) throw new ArgumentNullException(nameof(packet));
+
+            var responsePacket = Activator.CreateInstance<TResponsePacket>();
+
+            if (responsePacket is IMqttPacketWithIdentifier responsePacketWithIdentifier)
+            {
+                var requestPacketWithIdentifier = packet as IMqttPacketWithIdentifier;
+                if (requestPacketWithIdentifier == null)
+                {
+                    throw new InvalidOperationException("Response packet has PacketIdentifier but request packet does not.");
+                }
+
+                responsePacketWithIdentifier.PacketIdentifier = requestPacketWithIdentifier.PacketIdentifier;
+            }
+
+            return responsePacket;
+        }
+    }
+}

MQTTnet.Core/Packets/MqttPingReqPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPingReqPacket : MqttBasePacket
+    public sealed class MqttPingReqPacket : MqttBasePacket
     {
         public override string ToString()
         {

MQTTnet.Core/Packets/MqttPingRespPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPingRespPacket : MqttBasePacket
+    public sealed class MqttPingRespPacket : MqttBasePacket
     {
         public override string ToString()
         {

MQTTnet.Core/Packets/MqttPubAckPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPubAckPacket : MqttBasePublishPacket
+    public sealed class MqttPubAckPacket : MqttBasePublishPacket
     {
     }
 }

MQTTnet.Core/Packets/MqttPubCompPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPubCompPacket : MqttBasePublishPacket
+    public sealed class MqttPubCompPacket : MqttBasePublishPacket
     {
     }
 }

MQTTnet.Core/Packets/MqttPubRecPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPubRecPacket : MqttBasePublishPacket
+    public sealed class MqttPubRecPacket : MqttBasePublishPacket
     {
     }
 }

MQTTnet.Core/Packets/MqttPubRelPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPubRelPacket : MqttBasePublishPacket
+    public sealed class MqttPubRelPacket : MqttBasePublishPacket
     {
     }
 }

MQTTnet.Core/Packets/MqttPublishPacket.cs

@@ -3,7 +3,7 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Packets
 {
-    public class MqttPublishPacket : MqttBasePublishPacket
+    public sealed class MqttPublishPacket : MqttBasePublishPacket
     {
         public bool Retain { get; set; }
 

MQTTnet.Core/Packets/MqttSubAckPacket.cs

@@ -4,7 +4,7 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Packets
 {
-    public class MqttSubAckPacket : MqttBasePacket, IPacketWithIdentifier
+    public sealed class MqttSubAckPacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
 

MQTTnet.Core/Packets/MqttSubscribePacket.cs

@@ -3,7 +3,7 @@ using System.Linq;
 
 namespace MQTTnet.Core.Packets
 {
-    public class MqttSubscribePacket : MqttBasePacket, IPacketWithIdentifier
+    public sealed class MqttSubscribePacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
         

MQTTnet.Core/Packets/MqttUnsubAckPacket.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Packets
 {
-    public class MqttUnsubAckPacket : MqttBasePacket, IPacketWithIdentifier
+    public sealed class MqttUnsubAckPacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
     }

MQTTnet.Core/Packets/MqttUnsubscribe.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Packets
 {
-    public class MqttUnsubscribePacket : MqttBasePacket, IPacketWithIdentifier
+    public sealed class MqttUnsubscribePacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
         

MQTTnet.Core/Packets/TopicFilter.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Packets
 {
-    public class TopicFilter
+    public sealed class TopicFilter
     {
         public TopicFilter(string topic, MqttQualityOfServiceLevel qualityOfServiceLevel)
         {

MQTTnet.Core/Properties/AssemblyInfo.cs

@@ -1,15 +0,0 @@
-using System.Reflection;
-using System.Runtime.InteropServices;
-
-[assembly: AssemblyTitle("MQTTnet")]
-[assembly: AssemblyDescription("The core library of MQTTnet")]
-[assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("Christian Kratky")]
-[assembly: AssemblyProduct("MQTTnet")]
-[assembly: AssemblyCopyright("Copyright © Christian Kratky 2016-2017")]
-[assembly: AssemblyTrademark("")]
-[assembly: AssemblyCulture("")]
-[assembly: ComVisible(false)]
-[assembly: Guid("0e10d0ea-8e4b-4903-ab9e-93a187d07922")]
-[assembly: AssemblyVersion("2.1.0.4")]
-[assembly: AssemblyFileVersion("2.1.0.4")]

MQTTnet.Core/Serializer/ByteReader.cs

@@ -2,41 +2,47 @@
 
 namespace MQTTnet.Core.Serializer
 {
-    public class ByteReader
+    public sealed class ByteReader
     {
+        private readonly int _source;
         private int _index;
-        private readonly int _byte;
 
-        public ByteReader(byte @byte)
+        public ByteReader(int source)
         {
-            _byte = @byte;
+            _source = source;
         }
 
         public bool Read()
         {
             if (_index >= 8)
             {
-                throw new InvalidOperationException("End of the byte reached.");
+                throw new InvalidOperationException("End of byte reached.");
             }
 
-            var result = ((1 << _index) & _byte) > 0;
+            var result = ((1 << _index) & _source) > 0;
             _index++;
-
             return result;
         }
 
-        public byte Read(int count)
+        public int Read(int count)
         {
+            if (_index + count > 8)
+            {
+                throw new InvalidOperationException("End of byte will be reached.");
+            }
+
             var result = 0;
             for (var i = 0; i < count; i++)
             {
-                if (Read())
+                if (((1 << _index) & _source) > 0)
                 {
                     result |= 1 << i;
                 }
+
+                _index++;
             }
 
-            return (byte)result;
+            return result;
         }
     }
 }

MQTTnet.Core/Serializer/ByteWriter.cs

@@ -2,14 +2,14 @@
 
 namespace MQTTnet.Core.Serializer
 {
-    public class ByteWriter
+    public sealed class ByteWriter
     {
         private int _index;
         private int _byte;
 
         public byte Value => (byte)_byte;
 
-        public void Write(byte @byte, int count)
+        public void Write(int @byte, int count)
         {
             for (var i = 0; i < count; i++)
             {

MQTTnet.Core/Serializer/DefaultMqttV311PacketSerializer.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Linq;
-using System.Net;
 using System.Text;
-using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Exceptions;
@@ -11,109 +9,81 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Serializer
 {
-    public class DefaultMqttV311PacketSerializer : IMqttPacketSerializer
+    public sealed class DefaultMqttV311PacketSerializer : IMqttPacketSerializer
     {
-        public async Task SerializeAsync(MqttBasePacket packet, IMqttCommunicationChannel destination)
+        public Task SerializeAsync(MqttBasePacket packet, IMqttCommunicationChannel destination)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
             if (destination == null) throw new ArgumentNullException(nameof(destination));
 
-            var connectPacket = packet as MqttConnectPacket;
-            if (connectPacket != null)
+            if (packet is MqttConnectPacket connectPacket)
             {
-                await SerializeAsync(connectPacket, destination);
-                return;
+                return SerializeAsync(connectPacket, destination);
             }
 
-            var connAckPacket = packet as MqttConnAckPacket;
-            if (connAckPacket != null)
+            if (packet is MqttConnAckPacket connAckPacket)
             {
-                await SerializeAsync(connAckPacket, destination);
-                return;
+                return SerializeAsync(connAckPacket, destination);
             }
 
-            var disconnectPacket = packet as MqttDisconnectPacket;
-            if (disconnectPacket != null)
+            if (packet is MqttDisconnectPacket disconnectPacket)
             {
-                await SerializeAsync(disconnectPacket, destination);
-                return;
+                return SerializeAsync(disconnectPacket, destination);
             }
 
-            var pingReqPacket = packet as MqttPingReqPacket;
-            if (pingReqPacket != null)
+            if (packet is MqttPingReqPacket pingReqPacket)
             {
-                await SerializeAsync(pingReqPacket, destination);
-                return;
+                return SerializeAsync(pingReqPacket, destination);
             }
 
-            var pingRespPacket = packet as MqttPingRespPacket;
-            if (pingRespPacket != null)
+            if (packet is MqttPingRespPacket pingRespPacket)
             {
-                await SerializeAsync(pingRespPacket, destination);
-                return;
+                return SerializeAsync(pingRespPacket, destination);
             }
 
-            var publishPacket = packet as MqttPublishPacket;
-            if (publishPacket != null)
+            if (packet is MqttPublishPacket publishPacket)
             {
-                await SerializeAsync(publishPacket, destination);
-                return;
+                return SerializeAsync(publishPacket, destination);
             }
 
-            var pubAckPacket = packet as MqttPubAckPacket;
-            if (pubAckPacket != null)
+            if (packet is MqttPubAckPacket pubAckPacket)
             {
-                await SerializeAsync(pubAckPacket, destination);
-                return;
+                return SerializeAsync(pubAckPacket, destination);
             }
 
-            var pubRecPacket = packet as MqttPubRecPacket;
-            if (pubRecPacket != null)
+            if (packet is MqttPubRecPacket pubRecPacket)
             {
-                await SerializeAsync(pubRecPacket, destination);
-                return;
+                return SerializeAsync(pubRecPacket, destination);
             }
 
-            var pubRelPacket = packet as MqttPubRelPacket;
-            if (pubRelPacket != null)
+            if (packet is MqttPubRelPacket pubRelPacket)
             {
-                await SerializeAsync(pubRelPacket, destination);
-                return;
+                return SerializeAsync(pubRelPacket, destination);
             }
 
-            var pubCompPacket = packet as MqttPubCompPacket;
-            if (pubCompPacket != null)
+            if (packet is MqttPubCompPacket pubCompPacket)
             {
-                await SerializeAsync(pubCompPacket, destination);
-                return;
+                return SerializeAsync(pubCompPacket, destination);
             }
 
-            var subscribePacket = packet as MqttSubscribePacket;
-            if (subscribePacket != null)
+            if (packet is MqttSubscribePacket subscribePacket)
             {
-                await SerializeAsync(subscribePacket, destination);
-                return;
+                return SerializeAsync(subscribePacket, destination);
             }
 
-            var subAckPacket = packet as MqttSubAckPacket;
-            if (subAckPacket != null)
+            if (packet is MqttSubAckPacket subAckPacket)
             {
-                await SerializeAsync(subAckPacket, destination);
-                return;
+                return SerializeAsync(subAckPacket, destination);
             }
 
-            var unsubscribePacket = packet as MqttUnsubscribePacket;
-            if (unsubscribePacket != null)
+            if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                await SerializeAsync(unsubscribePacket, destination);
-                return;
+                return SerializeAsync(unsubscribePacket, destination);
             }
 
-            var unsubAckPacket = packet as MqttUnsubAckPacket;
-            if (unsubAckPacket != null)
+            if (packet is MqttUnsubAckPacket unsubAckPacket)
             {
-                await SerializeAsync(unsubAckPacket, destination);
-                return;
+                return SerializeAsync(unsubAckPacket, destination);
             }
 
             throw new MqttProtocolViolationException("Packet type invalid.");
@@ -216,13 +186,13 @@ namespace MQTTnet.Core.Serializer
 
                     default:
                         {
-                            throw new ProtocolViolationException();
+                            throw new MqttProtocolViolationException($"Packet type ({(int)mqttPacketReader.ControlPacketType}) not supported.");
                         }
                 }
             }
         }
 
-        private async Task<MqttBasePacket> DeserializeUnsubscribeAsync(MqttPacketReader reader)
+        private static async Task<MqttBasePacket> DeserializeUnsubscribeAsync(MqttPacketReader reader)
         {
             var packet = new MqttUnsubscribePacket
             {
@@ -237,7 +207,7 @@ namespace MQTTnet.Core.Serializer
             return packet;
         }
 
-        private async Task<MqttBasePacket> DeserializeSubscribeAsync(MqttPacketReader reader)
+        private static async Task<MqttBasePacket> DeserializeSubscribeAsync(MqttPacketReader reader)
         {
             var packet = new MqttSubscribePacket
             {
@@ -254,7 +224,7 @@ namespace MQTTnet.Core.Serializer
             return packet;
         }
 
-        private async Task<MqttBasePacket> DeserializePublishAsync(MqttPacketReader reader)
+        private static async Task<MqttBasePacket> DeserializePublishAsync(MqttPacketReader reader)
         {
             var fixedHeader = new ByteReader(reader.FixedHeader);
             var retain = fixedHeader.Read();
@@ -282,17 +252,15 @@ namespace MQTTnet.Core.Serializer
             return packet;
         }
 
-        private async Task<MqttBasePacket> DeserializeConnectAsync(MqttPacketReader reader)
+        private static async Task<MqttBasePacket> DeserializeConnectAsync(MqttPacketReader reader)
         {
-            var packet = new MqttConnectPacket();
-
-            await reader.ReadRemainingDataByteAsync();
-            await reader.ReadRemainingDataByteAsync();
+            await reader.ReadRemainingDataAsync(2); // Skip 2 bytes
+            
             var protocolName = await reader.ReadRemainingDataAsync(4);
 
             if (Encoding.UTF8.GetString(protocolName, 0, protocolName.Length) != "MQTT")
             {
-                throw new ProtocolViolationException("Protocol name is not 'MQTT'.");
+                throw new MqttProtocolViolationException("Protocol name is not 'MQTT'.");
             }
 
             var protocolLevel = await reader.ReadRemainingDataByteAsync();
@@ -300,7 +268,12 @@ namespace MQTTnet.Core.Serializer
 
             var connectFlagsReader = new ByteReader(connectFlags);
             connectFlagsReader.Read(); // Reserved.
-            packet.CleanSession = connectFlagsReader.Read();
+
+            var packet = new MqttConnectPacket
+            {
+                CleanSession = connectFlagsReader.Read()
+            };
+
             var willFlag = connectFlagsReader.Read();
             var willQoS = connectFlagsReader.Read(2);
             var willRetain = connectFlagsReader.Read();
@@ -333,7 +306,7 @@ namespace MQTTnet.Core.Serializer
             return packet;
         }
 
-        private async Task<MqttBasePacket> DeserializeSubAck(MqttPacketReader reader)
+        private static async Task<MqttBasePacket> DeserializeSubAck(MqttPacketReader reader)
         {
             var packet = new MqttSubAckPacket
             {
@@ -348,7 +321,7 @@ namespace MQTTnet.Core.Serializer
             return packet;
         }
 
-        private async Task<MqttBasePacket> DeserializeConnAck(MqttPacketReader reader)
+        private static async Task<MqttBasePacket> DeserializeConnAck(MqttPacketReader reader)
         {
             var variableHeader1 = await reader.ReadRemainingDataByteAsync();
             var variableHeader2 = await reader.ReadRemainingDataByteAsync();
@@ -362,40 +335,33 @@ namespace MQTTnet.Core.Serializer
             return packet;
         }
 
-        private void ValidateConnectPacket(MqttConnectPacket packet)
+        private static void ValidateConnectPacket(MqttConnectPacket packet)
         {
             if (string.IsNullOrEmpty(packet.ClientId) && !packet.CleanSession)
             {
-                throw new ProtocolViolationException("CleanSession must be set if ClientId is empty [MQTT-3.1.3-7].");
-            }
-
-            if (!string.IsNullOrEmpty(packet.ClientId) && !Regex.IsMatch(packet.ClientId, "^[a-zA-Z0-9]*$"))
-            {
-                throw new ProtocolViolationException("ClientId contains invalid characters [MQTT-3.1.3-5].");
+                throw new MqttProtocolViolationException("CleanSession must be set if ClientId is empty [MQTT-3.1.3-7].");
             }
         }
 
-        private void ValidatePublishPacket(MqttPublishPacket packet)
+        private static void ValidatePublishPacket(MqttPublishPacket packet)
         {
             if (packet.QualityOfServiceLevel == 0 && packet.Dup)
             {
-                throw new ProtocolViolationException("Dup flag must be false for QoS 0 packets [MQTT-3.3.1-2].");
+                throw new MqttProtocolViolationException("Dup flag must be false for QoS 0 packets [MQTT-3.3.1-2].");
             }
         }
 
-        private async Task SerializeAsync(MqttConnectPacket packet, IMqttCommunicationChannel destination)
+        private static readonly byte[] MqttPrefix = Encoding.UTF8.GetBytes("MQTT");
+
+        private static Task SerializeAsync(MqttConnectPacket packet, IMqttCommunicationChannel destination)
         {
             ValidateConnectPacket(packet);
 
             using (var output = new MqttPacketWriter())
             {
                 // Write variable header
-                output.Write(0x00); // 3.1.2.1 Protocol Name
-                output.Write(0x04); // ""
-                output.Write('M');
-                output.Write('Q');
-                output.Write('T');
-                output.Write('T');
+                output.Write(0x00, 0x04); // 3.1.2.1 Protocol Name
+                output.Write(MqttPrefix);
                 output.Write(0x04); // 3.1.2.2 Protocol Level
 
                 var connectFlags = new ByteWriter(); // 3.1.2.3 Connect Flags
@@ -405,7 +371,7 @@ namespace MQTTnet.Core.Serializer
 
                 if (packet.WillMessage != null)
                 {
-                    connectFlags.Write((byte)packet.WillMessage.QualityOfServiceLevel, 2);
+                    connectFlags.Write((int)packet.WillMessage.QualityOfServiceLevel, 2);
                     connectFlags.Write(packet.WillMessage.Retain);
                 }
                 else
@@ -413,7 +379,7 @@ namespace MQTTnet.Core.Serializer
                     connectFlags.Write(0, 2);
                     connectFlags.Write(false);
                 }
-
+                
                 connectFlags.Write(packet.Password != null);
                 connectFlags.Write(packet.Username != null);
 
@@ -438,11 +404,11 @@ namespace MQTTnet.Core.Serializer
                 }
 
                 output.InjectFixedHeader(MqttControlPacketType.Connect);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttConnAckPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttConnAckPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
@@ -453,26 +419,26 @@ namespace MQTTnet.Core.Serializer
                 output.Write((byte)packet.ConnectReturnCode);
 
                 output.InjectFixedHeader(MqttControlPacketType.ConnAck);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttDisconnectPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttDisconnectPacket packet, IMqttCommunicationChannel destination)
         {
-            await SerializeEmptyPacketAsync(MqttControlPacketType.Disconnect, destination);
+            return SerializeEmptyPacketAsync(MqttControlPacketType.Disconnect, destination);
         }
 
-        private async Task SerializeAsync(MqttPingReqPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttPingReqPacket packet, IMqttCommunicationChannel destination)
         {
-            await SerializeEmptyPacketAsync(MqttControlPacketType.PingReq, destination);
+            return SerializeEmptyPacketAsync(MqttControlPacketType.PingReq, destination);
         }
 
-        private async Task SerializeAsync(MqttPingRespPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttPingRespPacket packet, IMqttCommunicationChannel destination)
         {
-            await SerializeEmptyPacketAsync(MqttControlPacketType.PingResp, destination);
+            return SerializeEmptyPacketAsync(MqttControlPacketType.PingResp, destination);
         }
 
-        private async Task SerializeAsync(MqttPublishPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttPublishPacket packet, IMqttCommunicationChannel destination)
         {
             ValidatePublishPacket(packet);
 
@@ -503,33 +469,33 @@ namespace MQTTnet.Core.Serializer
                 fixedHeader.Write(packet.Dup);
 
                 output.InjectFixedHeader(MqttControlPacketType.Publish, fixedHeader.Value);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttPubAckPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttPubAckPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
                 output.Write(packet.PacketIdentifier);
 
                 output.InjectFixedHeader(MqttControlPacketType.PubAck);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttPubRecPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttPubRecPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
                 output.Write(packet.PacketIdentifier);
 
                 output.InjectFixedHeader(MqttControlPacketType.PubRec);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttPubRelPacket packet, IMqttCommunicationChannel destination)
+        private static async Task SerializeAsync(MqttPubRelPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
@@ -540,24 +506,24 @@ namespace MQTTnet.Core.Serializer
             }
         }
 
-        private async Task SerializeAsync(MqttPubCompPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttPubCompPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
                 output.Write(packet.PacketIdentifier);
 
                 output.InjectFixedHeader(MqttControlPacketType.PubComp);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttSubscribePacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttSubscribePacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
                 output.Write(packet.PacketIdentifier);
 
-                if (packet.TopicFilters?.Any() == true)
+                if (packet.TopicFilters?.Count > 0)
                 {
                     foreach (var topicFilter in packet.TopicFilters)
                     {
@@ -567,11 +533,11 @@ namespace MQTTnet.Core.Serializer
                 }
 
                 output.InjectFixedHeader(MqttControlPacketType.Subscribe, 0x02);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttSubAckPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttSubAckPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
@@ -586,11 +552,11 @@ namespace MQTTnet.Core.Serializer
                 }
 
                 output.InjectFixedHeader(MqttControlPacketType.SubAck);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttUnsubscribePacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttUnsubscribePacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
@@ -605,27 +571,27 @@ namespace MQTTnet.Core.Serializer
                 }
 
                 output.InjectFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeAsync(MqttUnsubAckPacket packet, IMqttCommunicationChannel destination)
+        private static Task SerializeAsync(MqttUnsubAckPacket packet, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
                 output.Write(packet.PacketIdentifier);
 
                 output.InjectFixedHeader(MqttControlPacketType.UnsubAck);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
 
-        private async Task SerializeEmptyPacketAsync(MqttControlPacketType type, IMqttCommunicationChannel destination)
+        private static Task SerializeEmptyPacketAsync(MqttControlPacketType type, IMqttCommunicationChannel destination)
         {
             using (var output = new MqttPacketWriter())
             {
                 output.InjectFixedHeader(type);
-                await output.WriteToAsync(destination);
+                return output.WriteToAsync(destination);
             }
         }
     }

MQTTnet.Core/Serializer/MqttPacketReader.cs

@@ -13,6 +13,8 @@ namespace MQTTnet.Core.Serializer
         private readonly MemoryStream _remainingData = new MemoryStream();
         private readonly IMqttCommunicationChannel _source;
 
+        private int _remainingLength;
+
         public MqttPacketReader(IMqttCommunicationChannel source)
         {
             _source = source ?? throw new ArgumentNullException(nameof(source));
@@ -22,8 +24,6 @@ namespace MQTTnet.Core.Serializer
 
         public byte FixedHeader { get; private set; }
 
-        public int RemainingLength { get; private set; }
-
         public bool EndOfRemainingData => _remainingData.Position == _remainingData.Length;
 
         public async Task ReadToEndAsync()
@@ -31,54 +31,18 @@ namespace MQTTnet.Core.Serializer
             await ReadFixedHeaderAsync();
             await ReadRemainingLengthAsync();
 
-            if (RemainingLength == 0)
+            if (_remainingLength == 0)
             {
                 return;
             }
 
-            var buffer = new byte[RemainingLength];
-            await _source.ReadAsync(buffer);
-
+            var buffer = new byte[_remainingLength];
+            await ReadFromSourceAsync(buffer);
+            
             _remainingData.Write(buffer, 0, buffer.Length);
             _remainingData.Position = 0;
         }
 
-        private async Task ReadFixedHeaderAsync()
-        {
-            FixedHeader = await ReadStreamByteAsync();
-
-            var byteReader = new ByteReader(FixedHeader);
-            byteReader.Read(4);
-            ControlPacketType = (MqttControlPacketType)byteReader.Read(4);
-        }
-
-        private async Task<byte> ReadStreamByteAsync()
-        {
-            var buffer = new byte[1];
-            await _source.ReadAsync(buffer);
-            return buffer[0];
-        }
-
-        private async Task ReadRemainingLengthAsync()
-        {
-            // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
-            var multiplier = 1;
-            var value = 0;
-            byte encodedByte;
-            do
-            {
-                encodedByte = await ReadStreamByteAsync();
-                value += (encodedByte & 127) * multiplier;
-                multiplier *= 128;
-                if (multiplier > 128 * 128 * 128)
-                {
-                    throw new MqttProtocolViolationException("Remaining length is ivalid.");
-                }
-            } while ((encodedByte & 128) != 0);
-
-            RemainingLength = value;
-        }
-
         public async Task<byte> ReadRemainingDataByteAsync()
         {
             return (await ReadRemainingDataAsync(1))[0];
@@ -107,18 +71,67 @@ namespace MQTTnet.Core.Serializer
             return await ReadRemainingDataAsync(length);
         }
 
-        public async Task<byte[]> ReadRemainingDataAsync()
+        public Task<byte[]> ReadRemainingDataAsync()
         {
-            return await ReadRemainingDataAsync(RemainingLength - (int)_remainingData.Position);
+            return ReadRemainingDataAsync(_remainingLength - (int)_remainingData.Position);
         }
 
         public async Task<byte[]> ReadRemainingDataAsync(int length)
         {
             var buffer = new byte[length];
             await _remainingData.ReadAsync(buffer, 0, buffer.Length);
+
             return buffer;
         }
 
+        private async Task ReadRemainingLengthAsync()
+        {
+            // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
+            var multiplier = 1;
+            var value = 0;
+            byte encodedByte;
+            do
+            {
+                encodedByte = await ReadStreamByteAsync();
+                value += (encodedByte & 127) * multiplier;
+                multiplier *= 128;
+                if (multiplier > 128 * 128 * 128)
+                {
+                    throw new MqttProtocolViolationException("Remaining length is ivalid.");
+                }
+            } while ((encodedByte & 128) != 0);
+
+            _remainingLength = value;
+        }
+
+        private Task ReadFromSourceAsync(byte[] buffer)
+        {
+            try
+            {
+                return _source.ReadAsync(buffer);
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        private async Task<byte> ReadStreamByteAsync()
+        {
+            var buffer = new byte[1];
+            await ReadFromSourceAsync(buffer);
+            return buffer[0];
+        }
+
+        private async Task ReadFixedHeaderAsync()
+        {
+            FixedHeader = await ReadStreamByteAsync();
+
+            var byteReader = new ByteReader(FixedHeader);
+            byteReader.Read(4);
+            ControlPacketType = (MqttControlPacketType)byteReader.Read(4);
+        }
+
         public void Dispose()
         {
             _remainingData?.Dispose();

MQTTnet.Core/Serializer/MqttPacketWriter.cs

@@ -9,43 +9,7 @@ namespace MQTTnet.Core.Serializer
 {
     public sealed class MqttPacketWriter : IDisposable
     {
-        private readonly MemoryStream _buffer = new MemoryStream();
-
-        public void InjectFixedHeader(byte fixedHeader)
-        {
-            if (_buffer.Length == 0)
-            {
-                Write(fixedHeader);
-                Write(0);
-                return;
-            }
-
-            var remainingLength = (int)_buffer.Length;
-            using (var buffer = new MemoryStream())
-            {
-                _buffer.WriteTo(buffer);
-                _buffer.SetLength(0);
-
-                _buffer.WriteByte(fixedHeader);
-
-                // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
-                var x = remainingLength;
-                do
-                {
-                    var encodedByte = (byte)(x % 128);
-                    x = x / 128;
-                    if (x > 0)
-                    {
-                        encodedByte = (byte)(encodedByte | 128);
-                    }
-
-                    _buffer.WriteByte(encodedByte);
-                } while (x > 0);
-
-                buffer.Position = 0;
-                buffer.WriteTo(_buffer);
-            }
-        }
+        private readonly MemoryStream _buffer = new MemoryStream(512);
 
         public void InjectFixedHeader(MqttControlPacketType packetType, byte flags = 0)
         {
@@ -59,11 +23,6 @@ namespace MQTTnet.Core.Serializer
             _buffer.WriteByte(value);
         }
 
-        public void Write(char value)
-        {
-            _buffer.WriteByte((byte)value);
-        }
-
         public void Write(ushort value)
         {
             var buffer = BitConverter.GetBytes(value);
@@ -73,11 +32,15 @@ namespace MQTTnet.Core.Serializer
 
         public void Write(ByteWriter value)
         {
+            if (value == null) throw new ArgumentNullException(nameof(value));
+
             _buffer.WriteByte(value.Value);
         }
 
-        public void Write(byte[] value)
+        public void Write(params byte[] value)
         {
+            if (value == null) throw new ArgumentNullException(nameof(value));
+
             _buffer.Write(value, 0, value.Length);
         }
 
@@ -94,14 +57,49 @@ namespace MQTTnet.Core.Serializer
             Write(value);
         }
 
+        public Task WriteToAsync(IMqttCommunicationChannel destination)
+        {
+            if (destination == null) throw new ArgumentNullException(nameof(destination));
+
+            return destination.WriteAsync(_buffer.ToArray());
+        }
+
         public void Dispose()
         {
             _buffer?.Dispose();
         }
 
-        public async Task WriteToAsync(IMqttCommunicationChannel destination)
+        private void InjectFixedHeader(byte fixedHeader)
         {
-            await destination.WriteAsync(_buffer.ToArray());
+            if (_buffer.Length == 0)
+            {
+                Write(fixedHeader);
+                Write(0);
+                return;
+            }
+
+            var backupBuffer = _buffer.ToArray();
+            var remainingLength = (int)_buffer.Length;
+
+            _buffer.SetLength(0);
+
+            _buffer.WriteByte(fixedHeader);
+
+            // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
+            var x = remainingLength;
+            do
+            {
+                var encodedByte = x % 128;
+                x = x / 128;
+                if (x > 0)
+                {
+                    encodedByte = encodedByte | 128;
+                }
+
+                _buffer.WriteByte((byte)encodedByte);
+            } while (x > 0);
+
+            _buffer.Write(backupBuffer, 0, backupBuffer.Length);
         }
     }
 }

MQTTnet.Core/Server/GetOrCreateClientSessionResult.cs

@@ -0,0 +1,9 @@
+namespace MQTTnet.Core.Server
+{
+    public sealed class GetOrCreateClientSessionResult
+    {
+        public bool IsExistingSession { get; set; }
+
+        public MqttClientSession Session { get; set; }
+    }
+}

MQTTnet.Core/Server/IMqttServer.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using MQTTnet.Core.Adapter;
+
+namespace MQTTnet.Core.Server
+{
+    public interface IMqttServer
+    {
+        event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
+        event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+
+        IList<string> GetConnectedClients();
+        void InjectClient(string identifier, IMqttCommunicationAdapter adapter);
+        void Publish(MqttApplicationMessage applicationMessage);
+        void Start();
+        void Stop();
+    }
+}

MQTTnet.Core/Server/MqttApplicationMessageReceivedEventArgs.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace MQTTnet.Core.Server
+{
+    public sealed class MqttApplicationMessageReceivedEventArgs : EventArgs
+    {
+        public MqttApplicationMessageReceivedEventArgs(string clientId, MqttApplicationMessage applicationMessage)
+        {
+            ClientId = clientId;
+            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+        }
+
+        public string ClientId { get; }
+
+        public MqttApplicationMessage ApplicationMessage { get; }
+    }
+}

MQTTnet.Core/Server/MqttClientMessageQueue.cs

@@ -11,16 +11,16 @@ using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Server
 {
-    public class MqttOutgoingPublicationsManager
+    public sealed class MqttClientMessageQueue
     {
-        private readonly AutoResetEvent _resetEvent = new AutoResetEvent(false);
         private readonly List<MqttClientPublishPacketContext> _pendingPublishPackets = new List<MqttClientPublishPacketContext>();
+        private readonly AsyncGate _gate = new AsyncGate();
 
         private readonly MqttServerOptions _options;
         private CancellationTokenSource _cancellationTokenSource;
         private IMqttCommunicationAdapter _adapter;
 
-        public MqttOutgoingPublicationsManager(MqttServerOptions options)
+        public MqttClientMessageQueue(MqttServerOptions options)
         {
             _options = options ?? throw new ArgumentNullException(nameof(options));
         }
@@ -29,30 +29,30 @@ namespace MQTTnet.Core.Server
         {
             if (_cancellationTokenSource != null)
             {
-                throw new InvalidOperationException($"{nameof(MqttOutgoingPublicationsManager)} already started.");
+                throw new InvalidOperationException($"{nameof(MqttClientMessageQueue)} already started.");
             }
 
             _adapter = adapter ?? throw new ArgumentNullException(nameof(adapter));
             _cancellationTokenSource = new CancellationTokenSource();
 
-            Task.Run(async () => await SendPendingPublishPacketsAsync(_cancellationTokenSource.Token)).Forget();
+            Task.Run(() => SendPendingPublishPacketsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
         }
 
         public void Stop()
         {
+            _adapter = null;
             _cancellationTokenSource?.Cancel();
             _cancellationTokenSource = null;
         }
 
-        public void Enqueue(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
+        public void Enqueue(MqttPublishPacket publishPacket)
         {
-            if (senderClientSession == null) throw new ArgumentNullException(nameof(senderClientSession));
             if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
 
             lock (_pendingPublishPackets)
             {
-                _pendingPublishPackets.Add(new MqttClientPublishPacketContext(senderClientSession, publishPacket));
-                _resetEvent.Set();
+                _pendingPublishPackets.Add(new MqttClientPublishPacketContext(publishPacket));
+                _gate.Set();
             }
         }
 
@@ -62,12 +62,17 @@ namespace MQTTnet.Core.Server
             {
                 try
                 {
-                    _resetEvent.WaitOne();
+                    await _gate.WaitOneAsync();
                     if (cancellationToken.IsCancellationRequested)
                     {
                         return;
                     }
 
+                    if (_adapter == null)
+                    {
+                        continue;
+                    }
+
                     List<MqttClientPublishPacketContext> pendingPublishPackets;
                     lock (_pendingPublishPackets)
                     {
@@ -81,7 +86,7 @@ namespace MQTTnet.Core.Server
                 }
                 catch (Exception e)
                 {
-                    MqttTrace.Error(nameof(MqttOutgoingPublicationsManager), e, "Error while sending pending publish packets.");
+                    MqttTrace.Error(nameof(MqttClientMessageQueue), e, "Error while sending pending publish packets.");
                 }
                 finally
                 {
@@ -106,11 +111,11 @@ namespace MQTTnet.Core.Server
             }
             catch (MqttCommunicationException exception)
             {
-                MqttTrace.Warning(nameof(MqttOutgoingPublicationsManager), exception, "Sending publish packet failed.");
+                MqttTrace.Warning(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttOutgoingPublicationsManager), exception, "Sending publish packet failed.");
+                MqttTrace.Error(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
             }
             finally
             {

MQTTnet.Core/Server/MqttClientPublishPacketContext.cs

@@ -3,16 +3,13 @@ using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Server
 {
-    public class MqttClientPublishPacketContext
+    public sealed class MqttClientPublishPacketContext
     {
-        public MqttClientPublishPacketContext(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
+        public MqttClientPublishPacketContext(MqttPublishPacket publishPacket)
         {
-            SenderClientSession = senderClientSession ?? throw new ArgumentNullException(nameof(senderClientSession));
             PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
         }
 
-        public MqttClientSession SenderClientSession { get; }
-
         public MqttPublishPacket PublishPacket { get; }
 
         public int SendTries { get; set; }

MQTTnet.Core/Server/MqttClientSession.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
@@ -11,12 +11,12 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Server
 {
-    public class MqttClientSession
+    public sealed class MqttClientSession : IDisposable
     {
-        private readonly ConcurrentDictionary<ushort, MqttPublishPacket> _pendingIncomingPublications = new ConcurrentDictionary<ushort, MqttPublishPacket>();
+        private readonly HashSet<ushort> _unacknowledgedPublishPackets = new HashSet<ushort>();
 
         private readonly MqttClientSubscriptionsManager _subscriptionsManager = new MqttClientSubscriptionsManager();
-        private readonly MqttOutgoingPublicationsManager _outgoingPublicationsManager;
+        private readonly MqttClientMessageQueue _messageQueue;
         private readonly Action<MqttClientSession, MqttPublishPacket> _publishPacketReceivedCallback;
         private readonly MqttServerOptions _options;
 
@@ -24,15 +24,20 @@ namespace MQTTnet.Core.Server
         private IMqttCommunicationAdapter _adapter;
         private string _identifier;
         private MqttApplicationMessage _willApplicationMessage;
-        
-        public MqttClientSession(MqttServerOptions options, Action<MqttClientSession, MqttPublishPacket> publishPacketReceivedCallback)
+
+        public MqttClientSession(string clientId, MqttServerOptions options, Action<MqttClientSession, MqttPublishPacket> publishPacketReceivedCallback)
         {
+            ClientId = clientId;
             _options = options ?? throw new ArgumentNullException(nameof(options));
             _publishPacketReceivedCallback = publishPacketReceivedCallback ?? throw new ArgumentNullException(nameof(publishPacketReceivedCallback));
-            
-            _outgoingPublicationsManager = new MqttOutgoingPublicationsManager(options);
+
+            _messageQueue = new MqttClientMessageQueue(options);
         }
 
+        public string ClientId { get; }
+
+        public bool IsConnected => _adapter != null;
+
         public async Task RunAsync(string identifier, MqttApplicationMessage willApplicationMessage, IMqttCommunicationAdapter adapter)
         {
             if (adapter == null) throw new ArgumentNullException(nameof(adapter));
@@ -45,7 +50,7 @@ namespace MQTTnet.Core.Server
                 _adapter = adapter;
                 _cancellationTokenSource = new CancellationTokenSource();
 
-                _outgoingPublicationsManager.Start(adapter);
+                _messageQueue.Start(adapter);
                 while (!_cancellationTokenSource.IsCancellationRequested)
                 {
                     var packet = await adapter.ReceivePacketAsync(TimeSpan.Zero);
@@ -65,8 +70,8 @@ namespace MQTTnet.Core.Server
                 {
                     _publishPacketReceivedCallback(this, _willApplicationMessage.ToPublishPacket());
                 }
-                
-                _outgoingPublicationsManager.Stop();
+
+                _messageQueue.Stop();
                 _cancellationTokenSource.Cancel();
                 _adapter = null;
 
@@ -74,79 +79,76 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        public void DispatchPublishPacket(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
+        public void EnqueuePublishPacket(MqttPublishPacket publishPacket)
         {
-            if (senderClientSession == null) throw new ArgumentNullException(nameof(senderClientSession));
             if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
 
-            if (!_subscriptionsManager.IsTopicSubscribed(publishPacket))
+            if (!_subscriptionsManager.IsSubscribed(publishPacket))
             {
                 return;
             }
 
-            _outgoingPublicationsManager.Enqueue(senderClientSession, publishPacket);
+            _messageQueue.Enqueue(publishPacket);
             MqttTrace.Verbose(nameof(MqttClientSession), $"Client '{_identifier}: Enqueued pending publish packet.");
         }
 
-        private async Task HandleIncomingPacketAsync(MqttBasePacket packet)
+        public void Dispose()
         {
-            var subscribePacket = packet as MqttSubscribePacket;
-            if (subscribePacket != null)
+            _cancellationTokenSource?.Cancel();
+            _cancellationTokenSource?.Dispose();
+        }
+
+        private Task HandleIncomingPacketAsync(MqttBasePacket packet)
+        {
+            if (packet is MqttSubscribePacket subscribePacket)
             {
-                await _adapter.SendPacketAsync(_subscriptionsManager.Subscribe(subscribePacket), _options.DefaultCommunicationTimeout);
-                return;
+                return _adapter.SendPacketAsync(_subscriptionsManager.Subscribe(subscribePacket), _options.DefaultCommunicationTimeout);
             }
 
-            var unsubscribePacket = packet as MqttUnsubscribePacket;
-            if (unsubscribePacket != null)
+            if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                await _adapter.SendPacketAsync(_subscriptionsManager.Unsubscribe(unsubscribePacket), _options.DefaultCommunicationTimeout);
-                return;
+                return _adapter.SendPacketAsync(_subscriptionsManager.Unsubscribe(unsubscribePacket), _options.DefaultCommunicationTimeout);
             }
 
-            var publishPacket = packet as MqttPublishPacket;
-            if (publishPacket != null)
+            if (packet is MqttPublishPacket publishPacket)
             {
-                await HandleIncomingPublishPacketAsync(publishPacket);
-                return;
+                return HandleIncomingPublishPacketAsync(publishPacket);
             }
 
-            var pubRelPacket = packet as MqttPubRelPacket;
-            if (pubRelPacket != null)
+            if (packet is MqttPubRelPacket pubRelPacket)
             {
-                await HandleIncomingPubRelPacketAsync(pubRelPacket);
-                return;
+                return HandleIncomingPubRelPacketAsync(pubRelPacket);
             }
 
-            var pubAckPacket = packet as MqttPubAckPacket;
-            if (pubAckPacket != null)
+            if (packet is MqttPubRecPacket pubRecPacket)
             {
-                await HandleIncomingPubAckPacketAsync(pubAckPacket);
-                return;
+                return _adapter.SendPacketAsync(pubRecPacket.CreateResponse<MqttPubRelPacket>(), _options.DefaultCommunicationTimeout);
+            }
+
+            if (packet is MqttPubAckPacket || packet is MqttPubCompPacket)
+            {
+                // Discard message.
+                return Task.FromResult((object)null);
             }
 
             if (packet is MqttPingReqPacket)
             {
-                await _adapter.SendPacketAsync(new MqttPingRespPacket(), _options.DefaultCommunicationTimeout);
-                return;
+                return _adapter.SendPacketAsync(new MqttPingRespPacket(), _options.DefaultCommunicationTimeout);
             }
 
             if (packet is MqttDisconnectPacket || packet is MqttConnectPacket)
             {
                 _cancellationTokenSource.Cancel();
-                return;
+                return Task.FromResult((object)null);
             }
 
             MqttTrace.Warning(nameof(MqttClientSession), $"Client '{_identifier}': Received not supported packet ({packet}). Closing connection.");
             _cancellationTokenSource.Cancel();
+
+            return Task.FromResult((object)null);
         }
 
-        private async Task HandleIncomingPubAckPacketAsync(MqttPubAckPacket pubAckPacket)
-        {
-            await Task.FromResult(0);
-        }
-
-        private async Task HandleIncomingPublishPacketAsync(MqttPublishPacket publishPacket)
+        private Task HandleIncomingPublishPacketAsync(MqttPublishPacket publishPacket)
         {
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
             {
@@ -154,26 +156,33 @@ namespace MQTTnet.Core.Server
             }
             else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
-                await _adapter.SendPacketAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
                 _publishPacketReceivedCallback(this, publishPacket);
+                return _adapter.SendPacketAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
             }
             else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
             {
-                _pendingIncomingPublications[publishPacket.PacketIdentifier] = publishPacket;
-                await _adapter.SendPacketAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                // QoS 2 is implement as method "B" [4.3.3 QoS 2: Exactly once delivery]
+                lock (_unacknowledgedPublishPackets)
+                {
+                    _unacknowledgedPublishPackets.Add(publishPacket.PacketIdentifier);
+                }
+
+                _publishPacketReceivedCallback(this, publishPacket);
+
+                return _adapter.SendPacketAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
             }
+
+            throw new MqttCommunicationException("Received not supported QoS level.");
         }
 
-        private async Task HandleIncomingPubRelPacketAsync(MqttPubRelPacket pubRelPacket)
+        private Task HandleIncomingPubRelPacketAsync(MqttPubRelPacket pubRelPacket)
         {
-            MqttPublishPacket publishPacket;
-            if (!_pendingIncomingPublications.TryRemove(pubRelPacket.PacketIdentifier, out publishPacket))
+            lock (_unacknowledgedPublishPackets)
             {
-                return;
+                _unacknowledgedPublishPackets.Remove(pubRelPacket.PacketIdentifier);
             }
 
-            await _adapter.SendPacketAsync(new MqttPubCompPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
-            _publishPacketReceivedCallback(this, publishPacket);
+            return _adapter.SendPacketAsync(new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
         }
     }
 }

MQTTnet.Core/Server/MqttClientSessionManager.cs

@@ -1,93 +0,0 @@
-using System;
-using System.Collections.Concurrent;
-using System.Linq;
-using System.Threading.Tasks;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Diagnostics;
-using MQTTnet.Core.Exceptions;
-using MQTTnet.Core.Packets;
-using MQTTnet.Core.Protocol;
-
-namespace MQTTnet.Core.Server
-{
-    public class MqttClientSessionManager
-    {
-        private readonly ConcurrentDictionary<string, MqttClientSession> _clientSessions = new ConcurrentDictionary<string, MqttClientSession>();
-        private readonly MqttServerOptions _options;
-
-        public MqttClientSessionManager(MqttServerOptions options)
-        {
-            _options = options ?? throw new ArgumentNullException(nameof(options));
-        }
-
-        public async Task RunClientSessionAsync(MqttClientConnectedEventArgs eventArgs)
-        {
-            try
-            {
-                var connectPacket = await eventArgs.ClientAdapter.ReceivePacketAsync(_options.DefaultCommunicationTimeout) as MqttConnectPacket;
-                if (connectPacket == null)
-                {
-                    throw new MqttProtocolViolationException("The first packet from a client must be a 'Connect' packet [MQTT-3.1.0-1].");
-                }
-
-                var connectReturnCode = MqttConnectReturnCode.ConnectionAccepted;
-                if (_options.ConnectionValidator != null)
-                {
-                    connectReturnCode = _options.ConnectionValidator(connectPacket);
-                }
-
-                MqttClientSession clientSession = null;
-                var isSessionPresent = _clientSessions.ContainsKey(connectPacket.ClientId);
-                if (isSessionPresent && connectPacket.CleanSession)
-                {
-                    MqttClientSession _;
-                    _clientSessions.TryRemove(connectPacket.ClientId, out _);
-                }
-                else if (!connectPacket.CleanSession)
-                {
-                    _clientSessions.TryGetValue(connectPacket.ClientId, out clientSession);
-                }
-
-                await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
-                {
-                    ConnectReturnCode = connectReturnCode,
-                    IsSessionPresent = clientSession != null
-                }, _options.DefaultCommunicationTimeout);
-
-                if (connectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
-                {
-                    return;
-                }
-
-                if (clientSession == null)
-                {
-                    clientSession = new MqttClientSession(_options, DispatchPublishPacket);
-                    _clientSessions.TryAdd(connectPacket.ClientId, clientSession);
-                }
-
-                await clientSession.RunAsync(eventArgs.Identifier, connectPacket.WillMessage, eventArgs.ClientAdapter);
-            }
-            catch (Exception exception)
-            {
-                MqttTrace.Error(nameof(MqttServer), exception, exception.Message);
-            }
-            finally
-            {
-                await eventArgs.ClientAdapter.DisconnectAsync();
-            }
-        }
-
-        public void Clear()
-        {
-            _clientSessions.Clear();
-        }
-
-        private void DispatchPublishPacket(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
-        {
-            foreach (var clientSession in _clientSessions.Values.ToList())
-            {
-                clientSession.DispatchPublishPacket(senderClientSession, publishPacket);
-            }
-        }
-    }
-}

MQTTnet.Core/Server/MqttClientSessionsManager.cs

@@ -0,0 +1,151 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Exceptions;
+using MQTTnet.Core.Internal;
+using MQTTnet.Core.Packets;
+using MQTTnet.Core.Protocol;
+
+namespace MQTTnet.Core.Server
+{
+    public sealed class MqttClientSessionsManager
+    {
+        private readonly object _syncRoot = new object();
+        private readonly Dictionary<string, MqttClientSession> _clientSessions = new Dictionary<string, MqttClientSession>();
+        private readonly MqttServerOptions _options;
+
+        public MqttClientSessionsManager(MqttServerOptions options)
+        {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
+
+        public async Task RunClientSessionAsync(MqttClientConnectedEventArgs eventArgs)
+        {
+            try
+            {
+                var connectPacket = await eventArgs.ClientAdapter.ReceivePacketAsync(_options.DefaultCommunicationTimeout) as MqttConnectPacket;
+                if (connectPacket == null)
+                {
+                    throw new MqttProtocolViolationException("The first packet from a client must be a 'CONNECT' packet [MQTT-3.1.0-1].");
+                }
+
+                var connectReturnCode = ValidateConnection(connectPacket);
+                if (connectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
+                {
+                    await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                    {
+                        ConnectReturnCode = connectReturnCode
+                    }, _options.DefaultCommunicationTimeout);
+
+                    return;
+                }
+
+                var clientSession = GetOrCreateClientSession(connectPacket);
+
+                await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                {
+                    ConnectReturnCode = connectReturnCode,
+                    IsSessionPresent = clientSession.IsExistingSession
+                }, _options.DefaultCommunicationTimeout);
+
+                await clientSession.Session.RunAsync(eventArgs.Identifier, connectPacket.WillMessage, eventArgs.ClientAdapter);
+            }
+            catch (Exception exception)
+            {
+                MqttTrace.Error(nameof(MqttServer), exception, exception.Message);
+            }
+            finally
+            {
+                await eventArgs.ClientAdapter.DisconnectAsync();
+            }
+        }
+
+        public void Clear()
+        {
+            lock (_syncRoot)
+            {
+                _clientSessions.Clear();
+            }
+        }
+
+        public IList<string> GetConnectedClients()
+        {
+            lock (_syncRoot)
+            {
+                return _clientSessions.Where(s => s.Value.IsConnected).Select(s => s.Key).ToList();
+            }
+        }
+
+        private MqttConnectReturnCode ValidateConnection(MqttConnectPacket connectPacket)
+        {
+            if (_options.ConnectionValidator != null)
+            {
+                return _options.ConnectionValidator(connectPacket);
+            }
+
+            return MqttConnectReturnCode.ConnectionAccepted;
+        }
+
+        private GetOrCreateClientSessionResult GetOrCreateClientSession(MqttConnectPacket connectPacket)
+        {
+            lock (_syncRoot)
+            {
+                MqttClientSession clientSession;
+                var isSessionPresent = _clientSessions.TryGetValue(connectPacket.ClientId, out clientSession);
+                if (isSessionPresent)
+                {
+                    if (connectPacket.CleanSession)
+                    {
+                        _clientSessions.Remove(connectPacket.ClientId);
+                        clientSession.Dispose();
+                        clientSession = null;
+                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Disposed existing session of client '{connectPacket.ClientId}'.");
+                    }
+                    else
+                    {
+                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Reusing existing session of client '{connectPacket.ClientId}'.");
+                    }
+                }
+
+                var isExistingSession = true;
+                if (clientSession == null)
+                {
+                    isExistingSession = false;
+
+                    clientSession = new MqttClientSession(connectPacket.ClientId, _options, DispatchPublishPacket);
+                    _clientSessions[connectPacket.ClientId] = clientSession;
+
+                    MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Created a new session for client '{connectPacket.ClientId}'.");
+                }
+
+                return new GetOrCreateClientSessionResult { IsExistingSession = isExistingSession, Session = clientSession };
+            }
+        }
+
+        public void DispatchPublishPacket(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
+        {
+            try
+            {
+                var eventArgs = new MqttApplicationMessageReceivedEventArgs(senderClientSession?.ClientId, publishPacket.ToApplicationMessage());
+                ApplicationMessageReceived?.Invoke(this, eventArgs);
+            }
+            catch (Exception exception)
+            {
+                MqttTrace.Error(nameof(MqttClientSessionsManager), exception, "Error while processing application message");
+            }
+
+            lock (_syncRoot)
+            {
+                foreach (var clientSession in _clientSessions.Values.ToList())
+                {
+                    clientSession.EnqueuePublishPacket(publishPacket);
+                }
+            }
+        }
+    }
+}

MQTTnet.Core/Server/MqttClientSubscriptionsManager.cs

@@ -1,23 +1,27 @@
 using System;
-using System.Collections.Concurrent;
+using System.Collections.Generic;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Server
 {
-    public class MqttClientSubscriptionsManager
+    public sealed class MqttClientSubscriptionsManager
     {
-        private readonly ConcurrentDictionary<string, MqttQualityOfServiceLevel> _subscribedTopics = new ConcurrentDictionary<string, MqttQualityOfServiceLevel>();
+        private readonly Dictionary<string, MqttQualityOfServiceLevel> _subscribedTopics = new Dictionary<string, MqttQualityOfServiceLevel>();
 
         public MqttSubAckPacket Subscribe(MqttSubscribePacket subscribePacket)
         {
             if (subscribePacket == null) throw new ArgumentNullException(nameof(subscribePacket));
 
             var responsePacket = subscribePacket.CreateResponse<MqttSubAckPacket>();
-            foreach (var topicFilter in subscribePacket.TopicFilters)
+
+            lock (_subscribedTopics)
             {
-                _subscribedTopics[topicFilter.Topic] = topicFilter.QualityOfServiceLevel;
-                responsePacket.SubscribeReturnCodes.Add(MqttSubscribeReturnCode.SuccessMaximumQoS1); // TODO: Add support for QoS 2.
+                foreach (var topicFilter in subscribePacket.TopicFilters)
+                {
+                    _subscribedTopics[topicFilter.Topic] = topicFilter.QualityOfServiceLevel;
+                    responsePacket.SubscribeReturnCodes.Add(MqttSubscribeReturnCode.SuccessMaximumQoS1); // TODO: Add support for QoS 2.
+                }
             }
 
             return responsePacket;
@@ -27,32 +31,37 @@ namespace MQTTnet.Core.Server
         {
             if (unsubscribePacket == null) throw new ArgumentNullException(nameof(unsubscribePacket));
 
-            foreach (var topicFilter in unsubscribePacket.TopicFilters)
+            lock (_subscribedTopics)
             {
-                MqttQualityOfServiceLevel _;
-                _subscribedTopics.TryRemove(topicFilter, out _);
+                foreach (var topicFilter in unsubscribePacket.TopicFilters)
+                {
+                    _subscribedTopics.Remove(topicFilter);
+                }
             }
 
             return unsubscribePacket.CreateResponse<MqttUnsubAckPacket>();
         }
 
-        public bool IsTopicSubscribed(MqttPublishPacket publishPacket)
+        public bool IsSubscribed(MqttPublishPacket publishPacket)
         {
             if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
 
-            foreach (var subscribedTopic in _subscribedTopics)
+            lock (_subscribedTopics)
             {
-                if (!MqttTopicFilterComparer.IsMatch(publishPacket.Topic, subscribedTopic.Key))
+                foreach (var subscribedTopic in _subscribedTopics)
                 {
-                    continue;
-                }
+                    if (publishPacket.QualityOfServiceLevel > subscribedTopic.Value)
+                    {
+                        continue;
+                    }
 
-                if (subscribedTopic.Value < publishPacket.QualityOfServiceLevel)
-                {
-                    continue;
-                }
+                    if (!MqttTopicFilterComparer.IsMatch(publishPacket.Topic, subscribedTopic.Key))
+                    {
+                        continue;
+                    }
 
-                return true;
+                    return true;
+                }
             }
 
             return false;

MQTTnet.Core/Server/MqttServer.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
@@ -7,53 +8,76 @@ using MQTTnet.Core.Internal;
 
 namespace MQTTnet.Core.Server
 {
-    public class MqttServer
+    public sealed class MqttServer : IMqttServer
     {
-        private readonly MqttClientSessionManager _clientSessionManager;
-        private readonly IMqttServerAdapter _adapter;
+        private readonly MqttClientSessionsManager _clientSessionsManager;
+        private readonly ICollection<IMqttServerAdapter> _adapters;
         private readonly MqttServerOptions _options;
 
         private CancellationTokenSource _cancellationTokenSource;
 
-        public MqttServer(MqttServerOptions options, IMqttServerAdapter adapter)
+        public MqttServer(MqttServerOptions options, ICollection<IMqttServerAdapter> adapters)
         {
             _options = options ?? throw new ArgumentNullException(nameof(options));
-            _adapter = adapter ?? throw new ArgumentNullException(nameof(adapter));
+            _adapters = adapters ?? throw new ArgumentNullException(nameof(adapters));
             
-            _clientSessionManager = new MqttClientSessionManager(options);
+            _clientSessionsManager = new MqttClientSessionsManager(options);
+            _clientSessionsManager.ApplicationMessageReceived += (s, e) => ApplicationMessageReceived?.Invoke(s, e);
+        }
+
+        public IList<string> GetConnectedClients()
+        {
+            return _clientSessionsManager.GetConnectedClients();
+        }
+
+        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+
+        public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
+
+        public void Publish(MqttApplicationMessage applicationMessage)
+        {
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
+
+            _clientSessionsManager.DispatchPublishPacket(null, applicationMessage.ToPublishPacket());
         }
 
         public void InjectClient(string identifier, IMqttCommunicationAdapter adapter)
         {
             if (adapter == null) throw new ArgumentNullException(nameof(adapter));
 
+            if (_cancellationTokenSource == null) throw new InvalidOperationException("The MQTT server is not started.");
+
             OnClientConnected(this, new MqttClientConnectedEventArgs(identifier, adapter));
         }
 
         public void Start()
         {
-            if (_cancellationTokenSource != null)
-            {
-                throw new InvalidOperationException("The server is already started.");
-            }
+            if (_cancellationTokenSource != null) throw new InvalidOperationException("The MQTT server is already started.");
 
             _cancellationTokenSource = new CancellationTokenSource();
 
-            _adapter.ClientConnected += OnClientConnected;
-            _adapter.Start(_options);
-
+            foreach (var adapter in _adapters)
+            {
+                adapter.ClientConnected += OnClientConnected;
+                adapter.Start(_options);
+            }
+            
             MqttTrace.Information(nameof(MqttServer), "Started.");
         }
 
         public void Stop()
         {
-            _cancellationTokenSource?.Cancel();
+            _cancellationTokenSource?.Cancel(false);
+            _cancellationTokenSource?.Dispose();
             _cancellationTokenSource = null;
 
-            _adapter.ClientConnected -= OnClientConnected;
-            _adapter.Stop();
+            foreach (var adapter in _adapters)
+            {
+                adapter.ClientConnected -= OnClientConnected;
+                adapter.Stop();
+            }
 
-            _clientSessionManager.Clear();
+            _clientSessionsManager.Clear();
 
             MqttTrace.Information(nameof(MqttServer), "Stopped.");
         }
@@ -61,7 +85,9 @@ namespace MQTTnet.Core.Server
         private void OnClientConnected(object sender, MqttClientConnectedEventArgs eventArgs)
         {
             MqttTrace.Information(nameof(MqttServer), $"Client '{eventArgs.Identifier}': Connected.");
-            Task.Run(async () => await _clientSessionManager.RunClientSessionAsync(eventArgs), _cancellationTokenSource.Token).Forget();
+            ClientConnected?.Invoke(this, eventArgs);
+
+            Task.Run(() => _clientSessionsManager.RunClientSessionAsync(eventArgs), _cancellationTokenSource.Token);
         }
     }
 }

MQTTnet.Core/Server/MqttServerDefaultEndpointOptions.cs

@@ -0,0 +1,9 @@
+namespace MQTTnet.Core.Server
+{
+    public sealed class MqttServerDefaultEndpointOptions
+    {
+        public bool IsEnabled { get; set; } = true;
+
+        public int? Port { get; set; }
+    }
+}

MQTTnet.Core/Server/MqttServerOptions.cs

@@ -4,13 +4,15 @@ using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Server
 {
-    public class MqttServerOptions
+    public sealed class MqttServerOptions
     {
-        public int Port { get; set; } = 1883;
+        public MqttServerDefaultEndpointOptions DefaultEndpointOptions { get; } = new MqttServerDefaultEndpointOptions();
 
+        public MqttServerTlsEndpointOptions TlsEndpointOptions { get; } = new MqttServerTlsEndpointOptions();
+        
         public int ConnectionBacklog { get; set; } = 10;
 
-        public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(10);
+        public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(15);
 
         public Func<MqttConnectPacket, MqttConnectReturnCode> ConnectionValidator { get; set; }
     }

MQTTnet.Core/Server/MqttServerOptionsExtensions.cs

@@ -0,0 +1,31 @@
+using System;
+
+namespace MQTTnet.Core.Server
+{
+    public static class MqttServerOptionsExtensions
+    {
+        public static int GetTlsEndpointPort(this MqttServerOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (!options.TlsEndpointOptions.Port.HasValue)
+            {
+                return 8883;
+            }
+
+            return options.TlsEndpointOptions.Port.Value;
+        }
+
+        public static int GetDefaultEndpointPort(this MqttServerOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (!options.DefaultEndpointOptions.Port.HasValue)
+            {
+                return 1883;
+            }
+
+            return options.DefaultEndpointOptions.Port.Value;
+        }
+    }
+}

MQTTnet.Core/Server/MqttServerTlsEndpointOptions.cs

@@ -0,0 +1,11 @@
+namespace MQTTnet.Core.Server
+{
+    public sealed class MqttServerTlsEndpointOptions
+    {
+        public bool IsEnabled { get; set; }
+
+        public int? Port { get; set; }
+
+        public byte[] Certificate { get; set; }
+    }
+}

MQTTnet.sln

@@ -1,12 +1,8 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26228.4
+VisualStudioVersion = 15.0.26430.15
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.Core", "MQTTnet.Core\MQTTnet.Core.csproj", "{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.TestMqttClient", "Tests\MQTTnet.TestMqttClient\MQTTnet.TestMqttClient.csproj", "{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}"
-EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.Core.Tests", "Tests\MQTTnet.Core.Tests\MQTTnet.Core.Tests.csproj", "{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.NetFramework", "Frameworks\MQTTnet.NetFramework\MQTTnet.NetFramework.csproj", "{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}"
@@ -15,11 +11,21 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.UniversalWindows",
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Tests", "Tests", "{9248C2E1-B9D6-40BF-81EC-86004D7765B4}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.NetCore", "Frameworks\MQTTnet.NetCore\MQTTnet.NetCore.csproj", "{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}"
-EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Frameworks", "Frameworks", "{32A630A7-2598-41D7-B625-204CD906F5FB}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.TestMqttServer", "Tests\MQTTnet.TestMqttServer\MQTTnet.TestMqttServer.csproj", "{6F8C0C0C-59EC-4921-9267-370AE113C34F}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Core", "MQTTnet.Core\MQTTnet.Core.csproj", "{2ECB99E4-72D0-4C23-99BA-93D511D3967D}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.TestApp.NetFramework", "Tests\MQTTnet.TestApp.NetFramework\MQTTnet.TestApp.NetFramework.csproj", "{D9D74F33-6943-49B2-B765-7BD589082098}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.TestApp.UniversalWindows", "Tests\MQTTnet.TestApp.UniversalWindows\MQTTnet.TestApp.UniversalWindows.csproj", "{FF1F72D6-9524-4422-9497-3CC0002216ED}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.NetStandard", "Frameworks\MQTTnet.Netstandard\MQTTnet.NetStandard.csproj", "{3587E506-55A2-4EB3-99C7-DC01E42D25D2}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Build", "Build", "{67C28AC1-BC3A-420A-BE9C-FA2401431CF9}"
+	ProjectSection(SolutionItems) = preProject
+		Build\build.ps1 = Build\build.ps1
+		Build\MQTTnet.nuspec = Build\MQTTnet.nuspec
+	EndProjectSection
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -33,70 +39,38 @@ Global
 		Release|x86 = Release|x86
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|ARM.ActiveCfg = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|ARM.Build.0 = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|x64.Build.0 = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Debug|x86.Build.0 = Debug|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|Any CPU.Build.0 = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|ARM.ActiveCfg = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|ARM.Build.0 = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|x64.ActiveCfg = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|x64.Build.0 = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|x86.ActiveCfg = Release|Any CPU
-		{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}.Release|x86.Build.0 = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|ARM.ActiveCfg = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|ARM.Build.0 = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|x64.Build.0 = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Debug|x86.Build.0 = Debug|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|Any CPU.Build.0 = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|ARM.ActiveCfg = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|ARM.Build.0 = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|x64.ActiveCfg = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|x64.Build.0 = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|x86.ActiveCfg = Release|Any CPU
-		{7B19B139-2E9D-4F1D-88B4-6180B4CF872A}.Release|x86.Build.0 = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|ARM.ActiveCfg = Debug|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|ARM.Build.0 = Debug|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.Build.0 = Debug|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.Build.0 = Debug|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.ActiveCfg = Debug|x64
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.Build.0 = Debug|x64
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.ActiveCfg = Debug|x86
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.Build.0 = Debug|x86
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|Any CPU.Build.0 = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|ARM.ActiveCfg = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|ARM.Build.0 = Release|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.ActiveCfg = Release|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.Build.0 = Release|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.ActiveCfg = Release|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.Build.0 = Release|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.ActiveCfg = Release|x64
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.Build.0 = Release|x64
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.ActiveCfg = Release|x86
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.Build.0 = Release|x86
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|ARM.ActiveCfg = Debug|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|ARM.Build.0 = Debug|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x64.Build.0 = Debug|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x86.Build.0 = Debug|Any CPU
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x64.ActiveCfg = Debug|x64
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x64.Build.0 = Debug|x64
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x86.ActiveCfg = Debug|x86
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|x86.Build.0 = Debug|x86
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|Any CPU.Build.0 = Release|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|ARM.ActiveCfg = Release|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|ARM.Build.0 = Release|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x64.ActiveCfg = Release|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x64.Build.0 = Release|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x86.ActiveCfg = Release|Any CPU
-		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x86.Build.0 = Release|Any CPU
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x64.ActiveCfg = Release|x64
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x64.Build.0 = Release|x64
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x86.ActiveCfg = Release|x86
+		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Release|x86.Build.0 = Release|x86
 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611}.Debug|ARM.ActiveCfg = Debug|ARM
@@ -113,48 +87,86 @@ Global
 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611}.Release|x64.Build.0 = Release|x64
 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611}.Release|x86.ActiveCfg = Release|x86
 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611}.Release|x86.Build.0 = Release|x86
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|ARM.ActiveCfg = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|ARM.Build.0 = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|x64.Build.0 = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Debug|x86.Build.0 = Debug|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|Any CPU.Build.0 = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|ARM.ActiveCfg = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|ARM.Build.0 = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|x64.ActiveCfg = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|x64.Build.0 = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|x86.ActiveCfg = Release|Any CPU
-		{88BE3FC9-79DC-4440-AC6B-C21BD97C6A3C}.Release|x86.Build.0 = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|ARM.ActiveCfg = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|ARM.Build.0 = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|x64.Build.0 = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Debug|x86.Build.0 = Debug|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|Any CPU.Build.0 = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|ARM.ActiveCfg = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|ARM.Build.0 = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|x64.ActiveCfg = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|x64.Build.0 = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|x86.ActiveCfg = Release|Any CPU
-		{6F8C0C0C-59EC-4921-9267-370AE113C34F}.Release|x86.Build.0 = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|ARM.ActiveCfg = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|ARM.Build.0 = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x64.ActiveCfg = Debug|x64
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x64.Build.0 = Debug|x64
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x86.ActiveCfg = Debug|x86
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x86.Build.0 = Debug|x86
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|ARM.ActiveCfg = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|ARM.Build.0 = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x64.ActiveCfg = Release|x64
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x64.Build.0 = Release|x64
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x86.ActiveCfg = Release|x86
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x86.Build.0 = Release|x86
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|ARM.ActiveCfg = Debug|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|ARM.Build.0 = Debug|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|x64.ActiveCfg = Debug|x64
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|x64.Build.0 = Debug|x64
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|x86.ActiveCfg = Debug|x86
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|x86.Build.0 = Debug|x86
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|ARM.ActiveCfg = Release|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|ARM.Build.0 = Release|Any CPU
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|x64.ActiveCfg = Release|x64
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|x64.Build.0 = Release|x64
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|x86.ActiveCfg = Release|x86
+		{D9D74F33-6943-49B2-B765-7BD589082098}.Release|x86.Build.0 = Release|x86
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|ARM.ActiveCfg = Debug|ARM
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|ARM.Build.0 = Debug|ARM
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|ARM.Deploy.0 = Debug|ARM
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|x64.ActiveCfg = Debug|x64
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+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Debug|x86.Deploy.0 = Debug|x86
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|Any CPU.ActiveCfg = Release|Any CPU
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+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|ARM.ActiveCfg = Release|ARM
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|ARM.Build.0 = Release|ARM
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|ARM.Deploy.0 = Release|ARM
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|x64.ActiveCfg = Release|x64
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+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|x86.Build.0 = Release|x86
+		{FF1F72D6-9524-4422-9497-3CC0002216ED}.Release|x86.Deploy.0 = Release|x86
+		{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}.Debug|ARM.ActiveCfg = Debug|Any CPU
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|ARM.Build.0 = Debug|Any CPU
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+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x64.Build.0 = Debug|x64
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x86.ActiveCfg = Debug|x86
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x86.Build.0 = Debug|x86
+		{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
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+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|ARM.Build.0 = Release|Any CPU
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+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|x64.Build.0 = Release|Any CPU
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|x86.ActiveCfg = Release|Any CPU
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
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 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
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 		{BD60C727-D8E8-40C3-B8E3-C95A864AE611} = {32A630A7-2598-41D7-B625-204CD906F5FB}
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-		{6F8C0C0C-59EC-4921-9267-370AE113C34F} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
+		{D9D74F33-6943-49B2-B765-7BD589082098} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
+		{FF1F72D6-9524-4422-9497-3CC0002216ED} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2} = {32A630A7-2598-41D7-B625-204CD906F5FB}
 	EndGlobalSection
 EndGlobal

README.md

@@ -2,19 +2,54 @@
 <img src="https://github.com/chkr1011/MQTTnet/blob/master/Images/Logo_128x128.png?raw=true" width="128">
 </p>
 
+[![NuGet Badge](https://buildstats.info/nuget/MQTTnet)](https://www.nuget.org/packages/MQTTnet)
+
 # MQTTnet
-MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server.
+MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server. The implementation is based on the documentation from http://mqtt.org/.
+
+## Features
+* MQTT client included
+* MQTT server (broker) included
+* TLS 1.2 support for client and server (but not UWP servers)
+* Async support
+* Rx support (via another project)
+* List of connected clients available (server only)
+* Extensible communication channels (i.e. In-Memory, TCP, TCP+SSL, WebSockets (not included in this project))
+* Server is able to publish its own messages (no loopback client required)
+* Access to internal trace messages
+* Extensible client credential validation (server only)
+* Unit tested (50+ tests)
+* Lightweight (only the low level implementation of MQTT, no overhead)
+* Interfaces included for mocking and testing
 
 ## Supported frameworks
+* .NET Standard 1.3+
+* .NET Core 1.1+
+* .NET Core App 1.1+
+* .NET Framework 4.5.2+ (x86, x64, AnyCPU)
+* Universal Windows (UWP) 10.0.10240+ (x86, x64, ARM, AnyCPU)
 
-* .NET Framework 4.5.2+
-* .NET Core 1.0+
-* Universal Windows (UWP) 10.0.10240+
+## Supported MQTT versions
+* 3.1.1
+
+## Nuget
+This library is available as a nuget package: https://www.nuget.org/packages/MQTTnet/
+
+## Contributions
+If you want to contribute to this project just create a pull request.
+
+## References
+This library is used in the following projects:
+
+* MQTT Client Rx (Wrapper for Reactive Extensions, https://github.com/1iveowl/MQTTClient.rx)
+* HA4IoT (Open Source Home Automation system for .NET, https://github.com/chkr1011/HA4IoT)
+
+If you use this library and want to see your project here please let me know.
 
 # MqttClient
 ## Example
 
-```c#
+```csharp
 var options = new MqttClientOptions
 {
     Server = "localhost"
@@ -88,7 +123,7 @@ while (true)
 
 ## Example 
 
-```c#
+```csharp
 var options = new MqttServerOptions
 {
     ConnectionValidator = p =>

Tests/MQTTnet.Core.Tests/MQTTnet.Core.Tests.csproj

@@ -9,7 +9,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>MQTTnet.Core.Tests</RootNamespace>
     <AssemblyName>MQTTnet.Core.Tests</AssemblyName>
-    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <TargetFrameworkProfile />
   </PropertyGroup>
@@ -30,6 +30,54 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|AnyCPU'">
+    <OutputPath>bin\Any CPU\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
+    <DebugSymbols>true</DebugSymbols>
+    <OutputPath>bin\x64\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <DebugType>full</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
+    <OutputPath>bin\x64\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x64'">
+    <OutputPath>bin\x64\Any CPU\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
+    <PlatformTarget>x86</PlatformTarget>
+    <OutputPath>bin\x86\Debug\</OutputPath>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x86'">
+    <PlatformTarget>x86</PlatformTarget>
+    <OutputPath>bin\x86\Release\</OutputPath>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x86'">
+    <PlatformTarget>x86</PlatformTarget>
+    <OutputPath>bin\x86\Any CPU\</OutputPath>
+  </PropertyGroup>
   <ItemGroup>
     <Reference Include="Microsoft.VisualStudio.QualityTools.UnitTestFramework, Version=10.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL" />
     <Reference Include="System" />
@@ -42,6 +90,7 @@
     <Compile Include="MqttServerTests.cs" />
     <Compile Include="MqttSubscriptionsManagerTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="TestMqttCommunicationAdapter.cs" />
     <Compile Include="TestMqttServerAdapter.cs" />
     <Compile Include="TopicFilterComparerTests.cs" />
   </ItemGroup>
@@ -50,7 +99,7 @@
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj">
-      <Project>{99C884F3-B4B9-417D-AA92-DC7DD1C4CFEE}</Project>
+      <Project>{2ecb99e4-72d0-4c23-99ba-93d511d3967d}</Project>
       <Name>MQTTnet.Core</Name>
     </ProjectReference>
   </ItemGroup>

Tests/MQTTnet.Core.Tests/MqttServerTests.cs

@@ -1,5 +1,4 @@
-using System;
-using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Core.Adapter;
@@ -49,11 +48,11 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public async Task MqttServer_WillMessage()
         {
-            var s = new MqttServer(new MqttServerOptions(), new TestMqttServerAdapter());
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
             s.Start();
 
             var willMessage = new MqttApplicationMessage("My/last/will", new byte[0], MqttQualityOfServiceLevel.AtMostOnce, false);
-            var c1 = ConnectTestClient("c1", null,  s);
+            var c1 = ConnectTestClient("c1", null, s);
             var c2 = ConnectTestClient("c2", willMessage, s);
 
             var receivedMessagesCount = 0;
@@ -69,10 +68,67 @@ namespace MQTTnet.Core.Tests
             Assert.AreEqual(1, receivedMessagesCount);
         }
 
-        private MqttClient ConnectTestClient(string clientId, MqttApplicationMessage willMessage, MqttServer server)
+        [TestMethod]
+        public async Task MqttServer_Unsubscribe()
         {
-            var adapterA = new TestMqttClientAdapter();
-            var adapterB = new TestMqttClientAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
+            s.Start();
+
+            var c1 = ConnectTestClient("c1", null, s);
+            var c2 = ConnectTestClient("c2", null, s);
+
+            var receivedMessagesCount = 0;
+            c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
+            
+            var message = new MqttApplicationMessage("a", new byte[0], MqttQualityOfServiceLevel.AtLeastOnce, false);
+
+            await c2.PublishAsync(message);
+            Assert.AreEqual(0, receivedMessagesCount);
+
+            await c1.SubscribeAsync(new TopicFilter("a", MqttQualityOfServiceLevel.AtLeastOnce));
+            await c2.PublishAsync(message);
+
+            await Task.Delay(500);
+            Assert.AreEqual(1, receivedMessagesCount);
+
+            await c1.Unsubscribe("a");
+            await c2.PublishAsync(message);
+
+            await Task.Delay(500);
+            Assert.AreEqual(1, receivedMessagesCount);
+
+            s.Stop();
+            await Task.Delay(500);
+
+            Assert.AreEqual(1, receivedMessagesCount);
+        }
+
+        [TestMethod]
+        public async Task MqttServer_Publish()
+        {
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
+            s.Start();
+
+            var c1 = ConnectTestClient("c1", null, s);
+
+            var receivedMessagesCount = 0;
+            c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
+
+            var message = new MqttApplicationMessage("a", new byte[0], MqttQualityOfServiceLevel.AtLeastOnce, false);
+            await c1.SubscribeAsync(new TopicFilter("a", MqttQualityOfServiceLevel.AtLeastOnce));
+
+            s.Publish(message);
+            await Task.Delay(500);
+
+            s.Stop();
+
+            Assert.AreEqual(1, receivedMessagesCount);
+        }
+
+        private static MqttClient ConnectTestClient(string clientId, MqttApplicationMessage willMessage, MqttServer server)
+        {
+            var adapterA = new TestMqttCommunicationAdapter();
+            var adapterB = new TestMqttCommunicationAdapter();
             adapterA.Partner = adapterB;
             adapterB.Partner = adapterA;
 
@@ -89,7 +145,7 @@ namespace MQTTnet.Core.Tests
             MqttQualityOfServiceLevel filterQualityOfServiceLevel,
             int expectedReceivedMessagesCount)
         {
-            var s = new MqttServer(new MqttServerOptions(), new TestMqttServerAdapter());
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
             s.Start();
 
             var c1 = ConnectTestClient("c1", null, s);
@@ -111,51 +167,4 @@ namespace MQTTnet.Core.Tests
             Assert.AreEqual(expectedReceivedMessagesCount, receivedMessagesCount);
         }
     }
-
-    public class TestMqttClientAdapter : IMqttCommunicationAdapter
-    {
-        private readonly BlockingCollection<MqttBasePacket> _incomingPackets = new BlockingCollection<MqttBasePacket>();
-
-        public TestMqttClientAdapter Partner { get; set; }
-
-        public async Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
-        {
-            await Task.FromResult(0);
-        }
-
-        public async Task DisconnectAsync()
-        {
-            await Task.FromResult(0);
-        }
-
-        public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
-        {
-            ThrowIfPartnerIsNull();
-
-            Partner.SendPacketInternal(packet);
-            await Task.FromResult(0);
-        }
-
-        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout)
-        {
-            ThrowIfPartnerIsNull();
-
-            return await Task.Run(() => _incomingPackets.Take());
-        }
-
-        private void SendPacketInternal(MqttBasePacket packet)
-        {
-            if (packet == null) throw new ArgumentNullException(nameof(packet));
-
-            _incomingPackets.Add(packet);
-        }
-
-        private void ThrowIfPartnerIsNull()
-        {
-            if (Partner == null)
-            {
-                throw new InvalidOperationException("Partner is not set.");
-            }
-        }
-    }
 }

Tests/MQTTnet.Core.Tests/MqttSubscriptionsManagerTests.cs

@@ -24,7 +24,7 @@ namespace MQTTnet.Core.Tests
                 QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce
             };
 
-            Assert.IsTrue(sm.IsTopicSubscribed(pp));
+            Assert.IsTrue(sm.IsSubscribed(pp));
         }
 
         [TestMethod]
@@ -43,7 +43,7 @@ namespace MQTTnet.Core.Tests
                 QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce
             };
 
-            Assert.IsFalse(sm.IsTopicSubscribed(pp));
+            Assert.IsFalse(sm.IsSubscribed(pp));
         }
 
         [TestMethod]
@@ -62,13 +62,13 @@ namespace MQTTnet.Core.Tests
                 QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce
             };
 
-            Assert.IsTrue(sm.IsTopicSubscribed(pp));
+            Assert.IsTrue(sm.IsSubscribed(pp));
 
             var up = new MqttUnsubscribePacket();
             up.TopicFilters.Add("A/B/C");
             sm.Unsubscribe(up);
 
-            Assert.IsFalse(sm.IsTopicSubscribed(pp));
+            Assert.IsFalse(sm.IsSubscribed(pp));
         }
     }
 }

Tests/MQTTnet.Core.Tests/Properties/AssemblyInfo.cs

@@ -11,5 +11,5 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyCulture("")]
 [assembly: ComVisible(false)]
 [assembly: Guid("a7ff0c91-25de-4ba6-b39e-f54e8dadf1cc")]
-[assembly: AssemblyVersion("2.1.0.4")]
-[assembly: AssemblyFileVersion("2.1.0.4")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]

Tests/MQTTnet.Core.Tests/TestMqttCommunicationAdapter.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Collections.Concurrent;
+using System.Threading.Tasks;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Tests
+{
+    public class TestMqttCommunicationAdapter : IMqttCommunicationAdapter
+    {
+        private readonly BlockingCollection<MqttBasePacket> _incomingPackets = new BlockingCollection<MqttBasePacket>();
+
+        public TestMqttCommunicationAdapter Partner { get; set; }
+
+        public async Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
+        {
+            await Task.FromResult(0);
+        }
+
+        public async Task DisconnectAsync()
+        {
+            await Task.FromResult(0);
+        }
+
+        public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
+        {
+            ThrowIfPartnerIsNull();
+
+            Partner.SendPacketInternal(packet);
+            await Task.FromResult(0);
+        }
+
+        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout)
+        {
+            ThrowIfPartnerIsNull();
+
+            return await Task.Run(() => _incomingPackets.Take());
+        }
+
+        private void SendPacketInternal(MqttBasePacket packet)
+        {
+            if (packet == null) throw new ArgumentNullException(nameof(packet));
+
+            _incomingPackets.Add(packet);
+        }
+
+        private void ThrowIfPartnerIsNull()
+        {
+            if (Partner == null)
+            {
+                throw new InvalidOperationException("Partner is not set.");
+            }
+        }
+    }
+}

Tests/MQTTnet.Core.Tests/TestMqttServerAdapter.cs

@@ -8,6 +8,11 @@ namespace MQTTnet.Core.Tests
     {
         public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
 
+        public void FireClientConnectedEvent(MqttClientConnectedEventArgs eventArgs)
+        {
+            ClientConnected?.Invoke(this, eventArgs);
+        }
+
         public void Start(MqttServerOptions options)
         {
         }

Tests/MQTTnet.TestApp.NetFramework/MQTTnet.TestApp.NetFramework.csproj

@@ -0,0 +1,102 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{D9D74F33-6943-49B2-B765-7BD589082098}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <RootNamespace>MQTTnet.TestApp.NetFramework</RootNamespace>
+    <AssemblyName>MQTTnet.TestApp.NetFramework</AssemblyName>
+    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
+    <DebugSymbols>true</DebugSymbols>
+    <OutputPath>bin\x86\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <DebugType>full</DebugType>
+    <PlatformTarget>x86</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+    <Prefer32Bit>true</Prefer32Bit>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x86'">
+    <OutputPath>bin\x86\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x86</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+    <Prefer32Bit>true</Prefer32Bit>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
+    <DebugSymbols>true</DebugSymbols>
+    <OutputPath>bin\x64\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <DebugType>full</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+    <Prefer32Bit>true</Prefer32Bit>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
+    <OutputPath>bin\x64\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+    <PlatformTarget>x64</PlatformTarget>
+    <ErrorReport>prompt</ErrorReport>
+    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+    <Prefer32Bit>true</Prefer32Bit>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Xml.Linq" />
+    <Reference Include="System.Data.DataSetExtensions" />
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System.Data" />
+    <Reference Include="System.Net.Http" />
+    <Reference Include="System.Xml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="App.config" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Frameworks\MQTTnet.NetFramework\MQTTnet.NetFramework.csproj">
+      <Project>{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}</Project>
+      <Name>MQTTnet.NetFramework</Name>
+    </ProjectReference>
+    <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj">
+      <Project>{2ecb99e4-72d0-4c23-99ba-93d511d3967d}</Project>
+      <Name>MQTTnet.Core</Name>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>

Tests/MQTTnet.TestApp.NetFramework/Program.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core;
 using MQTTnet.Core.Client;
@@ -9,16 +10,29 @@ using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
 using MQTTnet.Core.Server;
 
-namespace MQTTnet.TestMqttClient
+namespace MQTTnet.TestApp.NetFramework
 {
     public static class Program
     {
-        public static void Main(string[] arguments)
+        public static void Main(string[] args)
         {
-            Task.Run(() => Run(arguments)).Wait();
+            Console.WriteLine("MQTTnet - TestApp.NetFramework");
+            Console.WriteLine("1 = Start client");
+            Console.WriteLine("2 = Start server");
+            var pressedKey = Console.ReadKey(true);
+            if (pressedKey.Key == ConsoleKey.D1)
+            {
+                Task.Run(() => RunClientAsync(args));
+                Thread.Sleep(Timeout.Infinite);
+            }
+            else if (pressedKey.Key == ConsoleKey.D2)
+            {
+                Task.Run(() => RunServerAsync(args));
+                Thread.Sleep(Timeout.Infinite);
+            }
         }
 
-        private static async Task Run(string[] arguments)
+        private static async Task RunClientAsync(string[] arguments)
         {
             MqttTrace.TraceMessagePublished += (s, e) =>
             {
@@ -28,12 +42,14 @@ namespace MQTTnet.TestMqttClient
                     Console.WriteLine(e.Exception);
                 }
             };
-                       
+
             try
             {
                 var options = new MqttClientOptions
                 {
-                    Server = "localhost"
+                    Server = "localhost",
+                    ClientId = "XYZ",
+                    CleanSession = true
                 };
 
                 var client = new MqttClientFactory().CreateMqttClient(options);
@@ -59,7 +75,7 @@ namespace MQTTnet.TestMqttClient
                     Console.WriteLine("### SUBSCRIBED ###");
                 };
 
-                client.Disconnected += async (s, e) => 
+                client.Disconnected += async (s, e) =>
                 {
                     Console.WriteLine("### DISCONNECTED FROM SERVER ###");
                     await Task.Delay(TimeSpan.FromSeconds(5));
@@ -78,9 +94,9 @@ namespace MQTTnet.TestMqttClient
                 {
                     await client.ConnectAsync();
                 }
-                catch
+                catch (Exception exception)
                 {
-                    Console.WriteLine("### CONNECTING FAILED ###");
+                    Console.WriteLine("### CONNECTING FAILED ###" + Environment.NewLine + exception);
                 }
 
                 Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
@@ -104,5 +120,50 @@ namespace MQTTnet.TestMqttClient
                 Console.WriteLine(exception);
             }
         }
+
+        private static void RunServerAsync(string[] arguments)
+        {
+            MqttTrace.TraceMessagePublished += (s, e) =>
+            {
+                Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
+                if (e.Exception != null)
+                {
+                    Console.WriteLine(e.Exception);
+                }
+            };
+
+            try
+            {
+                var options = new MqttServerOptions
+                {
+                    ConnectionValidator = p =>
+                    {
+                        if (p.ClientId == "SpecialClient")
+                        {
+                            if (p.Username != "USER" || p.Password != "PASS")
+                            {
+                                return MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;
+                            }
+                        }
+
+                        return MqttConnectReturnCode.ConnectionAccepted;
+                    }
+                };
+
+                var mqttServer = new MqttServerFactory().CreateMqttServer(options);
+                mqttServer.Start();
+
+                Console.WriteLine("Press any key to exit.");
+                Console.ReadLine();
+
+                mqttServer.Stop();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+
+            Console.ReadLine();
+        }
     }
 }

Tests/MQTTnet.TestApp.NetFramework/Properties/AssemblyInfo.cs

@@ -1,7 +1,7 @@
 using System.Reflection;
 using System.Runtime.InteropServices;
 
-[assembly: AssemblyTitle("MQTTnet.TestMqttClient")]
+[assembly: AssemblyTitle("MQTTnet.TestApp.NetFramework")]
 [assembly: AssemblyDescription("")]
 [assembly: AssemblyConfiguration("")]
 [assembly: AssemblyCompany("Christian Kratky")]

Tests/MQTTnet.TestApp.UniversalWindows/App.xaml

@@ -0,0 +1,8 @@
+<Application
+    x:Class="MQTTnet.TestApp.UniversalWindows.App"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:MQTTnet.TestApp.UniversalWindows"
+    RequestedTheme="Light">
+
+</Application>

Tests/MQTTnet.TestApp.UniversalWindows/App.xaml.cs

@@ -0,0 +1,100 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.ApplicationModel;
+using Windows.ApplicationModel.Activation;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+
+namespace MQTTnet.TestApp.UniversalWindows
+{
+    /// <summary>
+    /// Provides application-specific behavior to supplement the default Application class.
+    /// </summary>
+    sealed partial class App : Application
+    {
+        /// <summary>
+        /// Initializes the singleton application object.  This is the first line of authored code
+        /// executed, and as such is the logical equivalent of main() or WinMain().
+        /// </summary>
+        public App()
+        {
+            this.InitializeComponent();
+            this.Suspending += OnSuspending;
+        }
+
+        /// <summary>
+        /// Invoked when the application is launched normally by the end user.  Other entry points
+        /// will be used such as when the application is launched to open a specific file.
+        /// </summary>
+        /// <param name="e">Details about the launch request and process.</param>
+        protected override void OnLaunched(LaunchActivatedEventArgs e)
+        {
+            Frame rootFrame = Window.Current.Content as Frame;
+
+            // Do not repeat app initialization when the Window already has content,
+            // just ensure that the window is active
+            if (rootFrame == null)
+            {
+                // Create a Frame to act as the navigation context and navigate to the first page
+                rootFrame = new Frame();
+
+                rootFrame.NavigationFailed += OnNavigationFailed;
+
+                if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
+                {
+                    //TODO: Load state from previously suspended application
+                }
+
+                // Place the frame in the current Window
+                Window.Current.Content = rootFrame;
+            }
+
+            if (e.PrelaunchActivated == false)
+            {
+                if (rootFrame.Content == null)
+                {
+                    // When the navigation stack isn't restored navigate to the first page,
+                    // configuring the new page by passing required information as a navigation
+                    // parameter
+                    rootFrame.Navigate(typeof(MainPage), e.Arguments);
+                }
+                // Ensure the current window is active
+                Window.Current.Activate();
+            }
+        }
+
+        /// <summary>
+        /// Invoked when Navigation to a certain page fails
+        /// </summary>
+        /// <param name="sender">The Frame which failed navigation</param>
+        /// <param name="e">Details about the navigation failure</param>
+        void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
+        {
+            throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
+        }
+
+        /// <summary>
+        /// Invoked when application execution is being suspended.  Application state is saved
+        /// without knowing whether the application will be terminated or resumed with the contents
+        /// of memory still intact.
+        /// </summary>
+        /// <param name="sender">The source of the suspend request.</param>
+        /// <param name="e">Details about the suspend request.</param>
+        private void OnSuspending(object sender, SuspendingEventArgs e)
+        {
+            var deferral = e.SuspendingOperation.GetDeferral();
+            //TODO: Save application state and stop any background activity
+            deferral.Complete();
+        }
+    }
+}