Merge from develop.

2026-10-15 00:15:15 +08:00 · 2018-11-16 22:16:21 +01:00
parent 5a59cd278c fcff3a2c8d
commit fed16d7710
50 changed files with 845 additions and 168 deletions
@@ -10,15 +10,14 @@
    <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>This is a support library to integrate MQTTnet into AspNetCore.</description>
-    <releaseNotes>* For more release notes please check the MQTTnet release notes.
-    </releaseNotes>
+    <releaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</releaseNotes>
    <copyright>Copyright Christian Kratky 2016-2018</copyright>
    <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags>
    <dependencies>
-      <dependency id="MQTTnet" version="2.8.2" />
-      <dependency id="Microsoft.AspNetCore.Connections.Abstractions" version="2.1.0" />
-      <dependency id="Microsoft.AspNetCore.WebSockets" version="2.0.1" />
-      <dependency id="Microsoft.Extensions.Hosting.Abstractions" version="2.0.1" />
+      <dependency id="MQTTnet" version="2.8.5-rc3" />
+      <dependency id="Microsoft.AspNetCore.Connections.Abstractions" version="2.1.3" />
+      <dependency id="Microsoft.AspNetCore.WebSockets" version="2.1.1" />
+      <dependency id="Microsoft.Extensions.Hosting.Abstractions" version="2.1.1" />
    </dependencies>
  </metadata>

@@ -10,12 +10,11 @@
    <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>This is an extension library which provides a managed MQTT client with additional features using MQTTnet.</description>
-    <releaseNotes>* For more release notes please check the MQTTnet release notes.
-    </releaseNotes>
+    <releaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</releaseNotes>
    <copyright>Copyright Christian Kratky 2016-2018</copyright>
    <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 
    <dependencies>
-      <dependency id="MQTTnet" version="2.8.2" />
+      <dependency id="MQTTnet" version="2.8.5-rc3" />
    </dependencies>
  </metadata>

@@ -10,12 +10,11 @@
    <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>This is an extension library which allows executing synchronous device calls including a response using MQTTnet.</description>
-    <releaseNotes>* For more release notes please check the MQTTnet release notes.
-    </releaseNotes>
+    <releaseNotes>For release notes please go to MQTTnet release notes (https://www.nuget.org/packages/MQTTnet/).</releaseNotes>
    <copyright>Copyright Christian Kratky 2016-2018</copyright>
    <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 
    <dependencies>
-      <dependency id="MQTTnet" version="2.8.2" />
+      <dependency id="MQTTnet" version="2.8.5-rc3" />
    </dependencies>
  </metadata>

@@ -10,15 +10,14 @@
    <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker).</description>
-    <releaseNotes>* [Core] Performance optimizations.
-* [Client] Added support for proxies when using web socket connections (thanks to PitySOFT).
-* [Client] Refactored TLS parameter usage and added more parameters (thanks to PitySOFT).
-* [Client] Fixed a deadlock when clients are disconnecting (thanks to @JanEggers).
-* [ManagedClient] Unsubscriptions are now pushed before subscriptions to support re-subscribing (thanks to @cstichlberger). 
-* [Server] Fixed an issue in client keep alive checks (thanks to @jenscski).
-* [Server] Changed the order of _ClientConnected_ and _ClientDisconnected_ events so that _ClientConnected_ is fired at first (thanks to @jenscski).
-* [Server] Fixed an iussue which lets the server stop processing messages when using the application message interceptor (thanks to @alamsor).
-* [Server] Fixed a deadlock when clients are disconnecting (thanks to @JanEggers).
+    <releaseNotes> * [Core] Updated nuget packages due to security issues.
+* [Client] Fixed wrong behavior of publish method when client is disconnecting (thanks to @PaulFake).
+* [ManagedClient] Added max pending messages count option.
+* [ManagedClient] Add pending messages overflow strategy option.
+* [Server] Added new method which exposes all retained messages.
+* [Server] Removed (wrong) setter from the server options interface.
+* [Server] fixed cpu spike in case a client disconnectes (issue 421).
+* [Server] fixed concurrent sends with Aspnetcore.Connections.Abstractions based transport.
    </releaseNotes>
    <copyright>Copyright Christian Kratky 2016-2018</copyright>
    <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 
@@ -27,7 +26,7 @@
        <dependency id="NETStandard.Library" version="1.3.0" />
        <dependency id="System.Net.Security" version="4.3.2" />
        <dependency id="System.Net.WebSockets" version="4.3.0" />
-        <dependency id="System.Net.WebSockets.Client" version="4.3.1" />      
+        <dependency id="System.Net.WebSockets.Client" version="4.3.2" />      
      </group>
      <group targetFramework="netstandard2.0">
        <dependency id="NETStandard.Library" version="2.0.0" />
@@ -36,7 +35,7 @@
        <dependency id="System.Net.WebSockets.Client" version="4.3.2" />
      </group>
      <group targetFramework="uap10.0">
-        <dependency id="Microsoft.NETCore.UniversalWindowsPlatform" version="6.1.4" />
+        <dependency id="Microsoft.NETCore.UniversalWindowsPlatform" version="6.1.9" />
      </group>
      <group targetFramework="net452">
      </group>
@@ -1,9 +1,11 @@
 <p align="center">
 <img src="https://github.com/chkr1011/MQTTnet/blob/master/Images/Logo_128x128.png?raw=true" width="128">
+<br/>
+<br/>
 </p>

 [![NuGet Badge](https://buildstats.info/nuget/MQTTnet)](https://www.nuget.org/packages/MQTTnet)
-[![Build status](https://ci.appveyor.com/api/projects/status/ycit86voxfevm2aa/branch/master?svg=true)](https://ci.appveyor.com/project/chkr1011/mqttnet/branch/develop)
+[![Build status](https://ci.appveyor.com/api/projects/status/ycit86voxfevm2aa/branch/master?svg=true)](https://ci.appveyor.com/project/chkr1011/mqttnet)
 [![BCH compliance](https://bettercodehub.com/edge/badge/chkr1011/MQTTnet?branch=master)](https://bettercodehub.com/)
 [![OpenCollective](https://opencollective.com/mqttnet/backers/badge.svg)](https://opencollective.com/mqttnet) 
 [![OpenCollective](https://opencollective.com/mqttnet/sponsors/badge.svg)](https://opencollective.com/mqttnet)
@@ -23,7 +25,7 @@ MQTTnet is a high performance .NET library for MQTT based communication. It prov
 * Performance optimized (processing ~70.000 messages / second)*
 * Interfaces included for mocking and testing
 * Access to internal trace messages
-* Unit tested (~90 tests)
+* Unit tested (~100 tests)

 \* Tested on local machine (Intel i7 8700K) with MQTTnet client and server running in the same process using the TCP channel. The app for verification is part of this repository and stored in _/Tests/MQTTnet.TestApp.NetCore_.

@@ -0,0 +1,15 @@
+using MQTTnet.Server;
+using System;
+
+namespace MQTTnet.AspNetCore
+{
+    public class AspNetMqttServerOptionsBuilder : MqttServerOptionsBuilder
+    {
+        public AspNetMqttServerOptionsBuilder(IServiceProvider serviceProvider)
+        {
+            ServiceProvider = serviceProvider;
+        }
+
+        public IServiceProvider ServiceProvider { get; }
+    }
+}
@@ -14,9 +14,9 @@
  </PropertyGroup>

  <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.Connections.Abstractions" Version="2.1.0" />
-    <PackageReference Include="Microsoft.AspNetCore.WebSockets" Version="2.0.1" />
-    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="2.0.1" />
+    <PackageReference Include="Microsoft.AspNetCore.Connections.Abstractions" Version="2.1.3" />
+    <PackageReference Include="Microsoft.AspNetCore.WebSockets" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="2.1.1" />
  </ItemGroup>

  <ItemGroup>
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Connections;
 using MQTTnet.Adapter;
 using MQTTnet.AspNetCore.Client.Tcp;
+using MQTTnet.Exceptions;
 using MQTTnet.Packets;
 using MQTTnet.Serializer;
 using System;
@@ -24,6 +25,8 @@ namespace MQTTnet.AspNetCore
        public event EventHandler ReadingPacketStarted;
        public event EventHandler ReadingPacketCompleted;

+        private readonly SemaphoreSlim _writerSemaphore = new SemaphoreSlim(1, 1);
+
        public Task ConnectAsync(TimeSpan timeout, CancellationToken cancellationToken)
        {
            if (Connection is TcpConnection tcp && !tcp.IsConnected)
@@ -57,7 +60,7 @@ namespace MQTTnet.AspNetCore
                    }
                    else
                    {
-                        readResult = await readTask;
+                        readResult = await readTask.ConfigureAwait(false);
                    }

                    var buffer = readResult.Buffer;
@@ -81,7 +84,7 @@ namespace MQTTnet.AspNetCore
                        }
                        else if (readResult.IsCompleted)
                        {
-                            break;
+                            throw new MqttCommunicationException("Connection Aborted");
                        }
                    }
                    finally
@@ -102,10 +105,20 @@ namespace MQTTnet.AspNetCore
            return null;
        }

-        public Task SendPacketAsync(MqttBasePacket packet, CancellationToken cancellationToken)
+        public async Task SendPacketAsync(MqttBasePacket packet, CancellationToken cancellationToken)
        {
-            var buffer = PacketSerializerAdapter.Serialize(packet);
-            return Connection.Transport.Output.WriteAsync(buffer.AsMemory(), cancellationToken).AsTask();
+            var buffer = PacketSerializer.Serialize(packet).AsMemory();
+            var output = Connection.Transport.Output;
+
+            await _writerSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
+            try
+            {
+                await output.WriteAsync(buffer, cancellationToken).ConfigureAwait(false);
+            }
+            finally
+            {
+                _writerSemaphore.Release();
+            }
        }

        public void Dispose()
@@ -20,14 +20,27 @@ namespace MQTTnet.AspNetCore

            return services;
        }
-        
+
        public static IServiceCollection AddHostedMqttServer(this IServiceCollection services, Action<MqttServerOptionsBuilder> configure)
        {
-            var builder = new MqttServerOptionsBuilder();
+            services.AddSingleton<IMqttServerOptions>(s => {
+                var builder = new MqttServerOptionsBuilder();
+                configure(builder);
+                return builder.Build();
+            });

-            configure(builder);
-            
-            services.AddSingleton<IMqttServerOptions>(builder.Build());
+            services.AddHostedMqttServer();
+
+            return services;
+        }
+
+        public static IServiceCollection AddHostedMqttServerWithServices(this IServiceCollection services, Action<AspNetMqttServerOptionsBuilder> configure)
+        {
+            services.AddSingleton<IMqttServerOptions>(s => {
+                var builder = new AspNetMqttServerOptionsBuilder(s);
+                configure(builder);
+                return builder.Build();
+            });

            services.AddHostedMqttServer();

@@ -0,0 +1,14 @@
+using System;
+
+namespace MQTTnet.Extensions.ManagedClient
+{
+    public class ApplicationMessageSkippedEventArgs : EventArgs
+    {
+        public ApplicationMessageSkippedEventArgs(ManagedMqttApplicationMessage applicationMessage)
+        {
+            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+        }
+
+        public ManagedMqttApplicationMessage ApplicationMessage { get; }
+    }
+}
@@ -15,6 +15,7 @@ namespace MQTTnet.Extensions.ManagedClient
        event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;

        event EventHandler<ApplicationMessageProcessedEventArgs> ApplicationMessageProcessed;
+        event EventHandler<ApplicationMessageSkippedEventArgs> ApplicationMessageSkipped;

        event EventHandler<MqttManagedProcessFailedEventArgs> ConnectingFailed;
        event EventHandler<MqttManagedProcessFailedEventArgs> SynchronizingSubscriptionsFailed;
@@ -1,5 +1,6 @@
 using System;
 using MQTTnet.Client;
+using MQTTnet.Server;

 namespace MQTTnet.Extensions.ManagedClient
 {
@@ -12,5 +13,9 @@ namespace MQTTnet.Extensions.ManagedClient
        TimeSpan ConnectionCheckInterval { get; }

        IManagedMqttClientStorage Storage { get; }
+
+        int MaxPendingMessages { get; }
+
+        MqttPendingMessagesOverflowStrategy PendingMessagesOverflowStrategy { get; }
    }
 }
@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -7,13 +6,17 @@ using System.Threading.Tasks;
 using MQTTnet.Client;
 using MQTTnet.Diagnostics;
 using MQTTnet.Exceptions;
+using MQTTnet.Internal;
 using MQTTnet.Protocol;
+using MQTTnet.Server;
+using MqttClientConnectedEventArgs = MQTTnet.Client.MqttClientConnectedEventArgs;
+using MqttClientDisconnectedEventArgs = MQTTnet.Client.MqttClientDisconnectedEventArgs;

 namespace MQTTnet.Extensions.ManagedClient
 {
    public class ManagedMqttClient : IManagedMqttClient
    {
-        private readonly BlockingCollection<ManagedMqttApplicationMessage> _messageQueue = new BlockingCollection<ManagedMqttApplicationMessage>();
+        private readonly BlockingQueue<ManagedMqttApplicationMessage> _messageQueue = new BlockingQueue<ManagedMqttApplicationMessage>();
        private readonly Dictionary<string, MqttQualityOfServiceLevel> _subscriptions = new Dictionary<string, MqttQualityOfServiceLevel>();
        private readonly HashSet<string> _unsubscriptions = new HashSet<string>();

@@ -50,6 +53,7 @@ namespace MQTTnet.Extensions.ManagedClient

        public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
        public event EventHandler<ApplicationMessageProcessedEventArgs> ApplicationMessageProcessed;
+        public event EventHandler<ApplicationMessageSkippedEventArgs> ApplicationMessageSkipped;

        public event EventHandler<MqttManagedProcessFailedEventArgs> ConnectingFailed;
        public event EventHandler<MqttManagedProcessFailedEventArgs> SynchronizingSubscriptionsFailed;
@@ -75,7 +79,7 @@ namespace MQTTnet.Extensions.ManagedClient

                foreach (var message in messages)
                {
-                    _messageQueue.Add(message);
+                    _messageQueue.Enqueue(message);
                }
            }

@@ -93,10 +97,7 @@ namespace MQTTnet.Extensions.ManagedClient
            StopPublishing();
            StopMaintainingConnection();

-            while (_messageQueue.Any())
-            {
-                _messageQueue.Take();
-            }
+            _messageQueue.Clear();

            return Task.FromResult(0);
        }
@@ -112,12 +113,38 @@ namespace MQTTnet.Extensions.ManagedClient
        {
            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));

-            if (_storageManager != null)
+            ManagedMqttApplicationMessage removedMessage = null;
+            lock (_messageQueue)
            {
-                await _storageManager.AddAsync(applicationMessage).ConfigureAwait(false);
+                if (_messageQueue.Count >= _options.MaxPendingMessages)
+                {
+                    if (_options.PendingMessagesOverflowStrategy == MqttPendingMessagesOverflowStrategy.DropNewMessage)
+                    {
+                        _logger.Verbose("Skipping publish of new application message because internal queue is full.");
+                        ApplicationMessageSkipped?.Invoke(this, new ApplicationMessageSkippedEventArgs(applicationMessage));
+                        return;
+                    }
+
+                    if (_options.PendingMessagesOverflowStrategy == MqttPendingMessagesOverflowStrategy.DropOldestQueuedMessage)
+                    {
+                        removedMessage = _messageQueue.RemoveFirst();
+                        _logger.Verbose("Removed oldest application message from internal queue because it is full.");
+                        ApplicationMessageSkipped?.Invoke(this, new ApplicationMessageSkippedEventArgs(removedMessage));
+                    }
+                }
+
+                _messageQueue.Enqueue(applicationMessage);
            }

-            _messageQueue.Add(applicationMessage);
+            if (_storageManager != null)
+            {
+                if (removedMessage != null)
+                {
+                    await _storageManager.RemoveAsync(removedMessage).ConfigureAwait(false);
+                }
+
+                await _storageManager.AddAsync(applicationMessage).ConfigureAwait(false);
+            }
        }

        public Task SubscribeAsync(IEnumerable<TopicFilter> topicFilters)
@@ -157,7 +184,6 @@ namespace MQTTnet.Extensions.ManagedClient

        public void Dispose()
        {
-            _messageQueue?.Dispose();
            _connectionCancellationToken?.Dispose();
            _publishingCancellationToken?.Dispose();
        }
@@ -226,9 +252,9 @@ namespace MQTTnet.Extensions.ManagedClient
        {
            try
            {
-                while (!cancellationToken.IsCancellationRequested)
+                while (!cancellationToken.IsCancellationRequested && _mqttClient.IsConnected)
                {
-                    var message = _messageQueue.Take(cancellationToken);
+                    var message = _messageQueue.Dequeue();
                    if (message == null)
                    {
                        continue;
@@ -268,7 +294,7 @@ namespace MQTTnet.Extensions.ManagedClient

                if (message.ApplicationMessage.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
                {
-                    _messageQueue.Add(message);
+                    _messageQueue.Enqueue(message);
                }
            }
            catch (Exception exception)
@@ -367,7 +393,6 @@ namespace MQTTnet.Extensions.ManagedClient
            }

            var cts = new CancellationTokenSource();
-
            _publishingCancellationToken = cts;

            Task.Factory.StartNew(() => PublishQueuedMessages(cts.Token), cts.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default);
@@ -1,5 +1,6 @@
 using System;
 using MQTTnet.Client;
+using MQTTnet.Server;

 namespace MQTTnet.Extensions.ManagedClient
 {
@@ -12,5 +13,9 @@ namespace MQTTnet.Extensions.ManagedClient
        public TimeSpan ConnectionCheckInterval { get; set; } = TimeSpan.FromSeconds(1);

        public IManagedMqttClientStorage Storage { get; set; }
+
+        public int MaxPendingMessages { get; set; } = int.MaxValue;
+
+        public MqttPendingMessagesOverflowStrategy PendingMessagesOverflowStrategy { get; set; } = MqttPendingMessagesOverflowStrategy.DropNewMessage;
    }
 }
@@ -1,5 +1,6 @@
 using System;
 using MQTTnet.Client;
+using MQTTnet.Server;

 namespace MQTTnet.Extensions.ManagedClient
 {
@@ -8,6 +9,18 @@ namespace MQTTnet.Extensions.ManagedClient
        private readonly ManagedMqttClientOptions _options = new ManagedMqttClientOptions();
        private MqttClientOptionsBuilder _clientOptionsBuilder;

+        public ManagedMqttClientOptionsBuilder WithMaxPendingMessages(int value)
+        {
+            _options.MaxPendingMessages = value;
+            return this;
+        }
+
+        public ManagedMqttClientOptionsBuilder WithPendingMessagesOverflowStrategy(MqttPendingMessagesOverflowStrategy value)
+        {
+            _options.PendingMessagesOverflowStrategy = value;
+            return this;
+        }
+
        public ManagedMqttClientOptionsBuilder WithAutoReconnectDelay(TimeSpan value)
        {
            _options.AutoReconnectDelay = value;
@@ -28,6 +28,8 @@ namespace MQTTnet.Extensions.ManagedClient

        public async Task AddAsync(ManagedMqttApplicationMessage applicationMessage)
        {
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
+
            using (await _messagesLock.LockAsync(CancellationToken.None).ConfigureAwait(false))
            {
                _messages.Add(applicationMessage);
@@ -37,6 +39,8 @@ namespace MQTTnet.Extensions.ManagedClient

        public async Task RemoveAsync(ManagedMqttApplicationMessage applicationMessage)
        {
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
+
            using (await _messagesLock.LockAsync(CancellationToken.None).ConfigureAwait(false))
            {
                var index = _messages.IndexOf(applicationMessage);
@@ -154,6 +154,9 @@ namespace MQTTnet.Adapter

                return packet;
            }
+            catch (OperationCanceledException)
+            {
+            }
            catch (Exception exception)
            {
                if (IsWrappedException(exception))
@@ -241,7 +244,8 @@ namespace MQTTnet.Adapter
        {
            if (exception is IOException && exception.InnerException is SocketException socketException)
            {
-                if (socketException.SocketErrorCode == SocketError.ConnectionAborted)
+                if (socketException.SocketErrorCode == SocketError.ConnectionAborted ||
+                    socketException.SocketErrorCode == SocketError.OperationAborted)
                {
                    throw new OperationCanceledException();
                }
@@ -7,5 +7,9 @@ namespace MQTTnet.Client
        IMqttClient CreateMqttClient();

        IMqttClient CreateMqttClient(IMqttNetLogger logger);
+
+        IMqttClient CreateMqttClient(IMqttClientAdapterFactory adapterFactory);
+
+        IMqttClient CreateMqttClient(IMqttNetLogger logger, IMqttClientAdapterFactory adapterFactory);
    }
 }
@@ -30,7 +30,7 @@ namespace MQTTnet.Client
        internal Task _keepAliveMessageSenderTask;
        private IMqttChannelAdapter _adapter;
        private bool _cleanDisconnectInitiated;
-        private TaskCompletionSource<bool> _disconnectReason;
+        private long _disconnectGate;

        public MqttClient(IMqttClientAdapterFactory channelFactory, IMqttNetLogger logger)
        {
@@ -55,12 +55,12 @@ namespace MQTTnet.Client

            try
            {
-                _cancellationTokenSource = new CancellationTokenSource();
-                _disconnectReason = new TaskCompletionSource<bool>();
                _options = options;
                _packetIdentifierProvider.Reset();
                _packetDispatcher.Reset();

+                _cancellationTokenSource = new CancellationTokenSource();
+                _disconnectGate = 0;
                _adapter = _adapterFactory.CreateClientAdapter(options, _logger);
                
                _logger.Verbose($"Trying to connect with server ({_options.ChannelOptions}).");
@@ -88,10 +88,12 @@ namespace MQTTnet.Client
            catch (Exception exception)
            {
                _logger.Error(exception, "Error while connecting with server.");
-                if (_disconnectReason.TrySetException(exception))
+
+                if (!DisconnectIsPending())
                {
                    await DisconnectInternalAsync(null, exception).ConfigureAwait(false);
                }
+
                throw;
            }
        }
@@ -109,7 +111,7 @@ namespace MQTTnet.Client
            }
            finally
            {
-                if (_disconnectReason.TrySetCanceled())
+                if (!DisconnectIsPending())
                {
                    await DisconnectInternalAsync(null, null).ConfigureAwait(false);
                }
@@ -184,10 +186,12 @@ namespace MQTTnet.Client

        public void Dispose()
        {
+            _cancellationTokenSource?.Cancel(false);
            _cancellationTokenSource?.Dispose();
            _cancellationTokenSource = null;

            _adapter?.Dispose();
+            _adapter = null;
        }

        private async Task<MqttV3ConnAckPacket> AuthenticateAsync(MqttApplicationMessage willApplicationMessage, CancellationToken cancellationToken)
@@ -213,7 +217,7 @@ namespace MQTTnet.Client

        private void ThrowIfNotConnected()
        {
-            if (!IsConnected) throw new MqttCommunicationException("The client is not connected.");
+            if (!IsConnected || Interlocked.Read(ref _disconnectGate) == 1) throw new MqttCommunicationException("The client is not connected.");
        }

        private void ThrowIfConnected(string message)
@@ -223,9 +227,10 @@ namespace MQTTnet.Client

        private async Task DisconnectInternalAsync(Task sender, Exception exception)
        {
-            InitiateDisconnect();
-
            var clientWasConnected = IsConnected;
+
+            InitiateDisconnect();
+            
            IsConnected = false;

            try
@@ -246,10 +251,7 @@ namespace MQTTnet.Client
            }
            finally
            {
-                _adapter?.Dispose();
-                _adapter = null;
-                _cancellationTokenSource?.Dispose();
-                _cancellationTokenSource = null;
+                Dispose();
                _cleanDisconnectInitiated = false;

                _logger.Info("Disconnected.");
@@ -263,16 +265,16 @@ namespace MQTTnet.Client
            {
                try
                {
-                    if (_cancellationTokenSource == null || _cancellationTokenSource.IsCancellationRequested)
+                    if (_cancellationTokenSource?.IsCancellationRequested == true)
                    {
                        return;
                    }

-                    _cancellationTokenSource.Cancel(false);
+                    _cancellationTokenSource?.Cancel(false);
                }
-                catch (Exception adapterException)
+                catch (Exception exception)
                {
-                    _logger.Warning(adapterException, "Error while initiating disconnect.");
+                    _logger.Warning(exception, "Error while initiating disconnect.");
                }
            }
        }
@@ -360,7 +362,7 @@ namespace MQTTnet.Client
                    _logger.Error(exception, "Unhandled exception while sending/receiving keep alive packets.");
                }

-                if (_disconnectReason.TrySetException(exception))
+                if (!DisconnectIsPending())
                {
                    await DisconnectInternalAsync(_keepAliveMessageSenderTask, exception).ConfigureAwait(false);
                }
@@ -379,8 +381,10 @@ namespace MQTTnet.Client
            {
                while (!cancellationToken.IsCancellationRequested)
                {
-                    var packet = await _adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
-                    if (packet != null)
+                    var packet = await _adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken)
+                        .ConfigureAwait(false);
+
+                    if (packet != null && !cancellationToken.IsCancellationRequested)
                    {
                        await ProcessReceivedPacketAsync(packet, cancellationToken).ConfigureAwait(false);
                    }
@@ -407,7 +411,7 @@ namespace MQTTnet.Client

                _packetDispatcher.Dispatch(exception);

-                if (_disconnectReason.TrySetException(exception))
+                if (!DisconnectIsPending())
                {
                    await DisconnectInternalAsync(_packetReceiverTask, exception).ConfigureAwait(false);
                }
@@ -493,16 +497,20 @@ namespace MQTTnet.Client

        private void StartReceivingPackets(CancellationToken cancellationToken)
        {
-            _packetReceiverTask = Task.Run(
+            _packetReceiverTask = Task.Factory.StartNew(
                () => ReceivePacketsAsync(cancellationToken),
-                cancellationToken);
+                cancellationToken,
+                TaskCreationOptions.LongRunning, 
+                TaskScheduler.Default);
        }

        private void StartSendingKeepAliveMessages(CancellationToken cancellationToken)
        {
-            _keepAliveMessageSenderTask = Task.Run(
+            _keepAliveMessageSenderTask = Task.Factory.StartNew(
                () => SendKeepAliveMessagesAsync(cancellationToken),
-                cancellationToken);
+                cancellationToken,
+                TaskCreationOptions.LongRunning,
+                TaskScheduler.Default);
        }

        private void FireApplicationMessageReceivedEvent(MqttPublishPacket publishPacket)
@@ -538,5 +546,10 @@ namespace MQTTnet.Client
            {
            }
        }
+
+        private bool DisconnectIsPending()
+        {
+            return Interlocked.CompareExchange(ref _disconnectGate, 1, 0) != 0;
+        }
    }
-}
+}
@@ -116,7 +116,7 @@ namespace MQTTnet.Implementations
                return true;
            }

-            if (chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.RevocationStatusUnknown || c.Status == X509ChainStatusFlags.Revoked || c.Status == X509ChainStatusFlags.RevocationStatusUnknown))
+            if (chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.RevocationStatusUnknown || c.Status == X509ChainStatusFlags.Revoked || c.Status == X509ChainStatusFlags.OfflineRevocation))
            {
                if (!_options.TlsOptions.IgnoreCertificateRevocationErrors)
                {
@@ -20,8 +20,8 @@ namespace MQTTnet.Implementations
        private readonly CancellationToken _cancellationToken;
        private readonly AddressFamily _addressFamily;
        private readonly MqttServerTcpEndpointBaseOptions _options;
+        private readonly MqttServerTlsTcpEndpointOptions _tlsOptions;
        private readonly X509Certificate2 _tlsCertificate;
-
        private Socket _socket;

        public MqttTcpServerListener(
@@ -36,6 +36,11 @@ namespace MQTTnet.Implementations
            _tlsCertificate = tlsCertificate;
            _cancellationToken = cancellationToken;
            _logger = logger.CreateChildLogger(nameof(MqttTcpServerListener));
+            
+            if (_options is MqttServerTlsTcpEndpointOptions tlsOptions)
+            {
+                _tlsOptions = tlsOptions;
+            }
        }

        public event EventHandler<MqttServerAdapterClientAcceptedEventArgs> ClientAccepted;
@@ -75,7 +80,7 @@ namespace MQTTnet.Implementations
                    if (_tlsCertificate != null)
                    {
                        sslStream = new SslStream(new NetworkStream(clientSocket), false);
-                        await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false).ConfigureAwait(false);
+                        await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, _tlsOptions.SslProtocol, false).ConfigureAwait(false);
                    }

                    _logger.Verbose("Client '{0}' accepted by TCP listener '{1}, {2}'.",
@@ -0,0 +1,78 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace MQTTnet.Internal
+{
+    public class BlockingQueue<TItem>
+    {
+        private readonly object _syncRoot = new object();
+        private readonly LinkedList<TItem> _items = new LinkedList<TItem>();
+        private readonly ManualResetEvent _gate = new ManualResetEvent(false);
+
+        public int Count
+        {
+            get
+            {
+                lock (_syncRoot)
+                {
+                    return _items.Count;
+                }
+            }
+        }
+
+        public void Enqueue(TItem item)
+        {
+            if (item == null) throw new ArgumentNullException(nameof(item));
+
+            lock (_syncRoot)
+            {
+                _items.AddLast(item);
+                _gate.Set();
+            }
+        }
+
+        public TItem Dequeue()
+        {
+            while (true)
+            {
+                lock (_syncRoot)
+                {
+                    if (_items.Count > 0)
+                    {
+                        var item = _items.First.Value;
+                        _items.RemoveFirst();
+
+                        return item;
+                    }
+
+                    if (_items.Count == 0)
+                    {
+                        _gate.Reset();
+                    }
+                }
+
+                _gate.WaitOne();
+            }
+        }
+
+        public TItem RemoveFirst()
+        {
+            lock (_syncRoot)
+            {
+                var item = _items.First;
+                _items.RemoveFirst();
+
+                return item.Value;
+            }
+        }
+
+        public void Clear()
+        {
+            lock (_syncRoot)
+            {
+                _items.Clear();
+            }
+        }
+    }
+}
@@ -54,7 +54,7 @@
  </ItemGroup>

  <ItemGroup Condition="'$(TargetFramework)'=='uap10.0'">
-    <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform" Version="6.1.5" />
+    <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform" Version="6.1.9" />
  </ItemGroup>

  <ItemGroup Condition="'$(TargetFramework)'=='net452'">
@@ -16,8 +16,14 @@ namespace MQTTnet.Server
        
        IMqttServerOptions Options { get; }

+        [Obsolete("This method is no longer async. Use the not async method.")]
        Task<IList<IMqttClientSessionStatus>> GetClientSessionsStatusAsync();

+        IList<IMqttClientSessionStatus> GetClientSessionsStatus();
+
+        IList<MqttApplicationMessage> GetRetainedMessages();
+        Task ClearRetainedMessagesAsync();
+
        Task SubscribeAsync(string clientId, IList<TopicFilter> topicFilters);
        Task UnsubscribeAsync(string clientId, IList<string> topicFilters);

@@ -8,6 +8,8 @@ namespace MQTTnet.Server
    {
        IMqttServer CreateMqttServer();

+        IMqttServer CreateMqttServer(IMqttNetLogger logger);
+
        IMqttServer CreateMqttServer(IEnumerable<IMqttServerAdapter> adapters, IMqttNetLogger logger);
    }
 }
@@ -14,7 +14,7 @@ namespace MQTTnet.Server
        Action<MqttConnectionValidatorContext> ConnectionValidator { get; }
        Action<MqttSubscriptionInterceptorContext> SubscriptionInterceptor { get; }
        Action<MqttApplicationMessageInterceptorContext> ApplicationMessageInterceptor { get; }
-        Action<MqttClientMessageQueueInterceptorContext> ClientMessageQueueInterceptor { get; set; }
+        Action<MqttClientMessageQueueInterceptorContext> ClientMessageQueueInterceptor { get; }

        MqttServerTcpEndpointOptions DefaultEndpointOptions { get; }
        MqttServerTlsTcpEndpointOptions TlsEndpointOptions { get; }
@@ -137,7 +137,9 @@ namespace MQTTnet.Server

                _cleanupHandle?.Dispose();
                _cleanupHandle = null;
-
+                
+                _adapter = null;
+                _cancellationTokenSource?.Cancel(false);
                _cancellationTokenSource?.Dispose();
                _cancellationTokenSource = null;
            }
@@ -289,7 +291,9 @@ namespace MQTTnet.Server
        {
            _pendingPacketsQueue?.Dispose();

+            _cancellationTokenSource?.Cancel ();
            _cancellationTokenSource?.Dispose();
+            _cancellationTokenSource = null;
        }

        private void ProcessReceivedPacket(IMqttChannelAdapter adapter, MqttBasePacket packet, CancellationToken cancellationToken)
@@ -66,7 +66,7 @@ namespace MQTTnet.Server
            return Task.Run(() => RunSession(clientAdapter, _cancellationToken), _cancellationToken);
        }

-        public Task<IList<IMqttClientSessionStatus>> GetClientStatusAsync()
+        public IList<IMqttClientSessionStatus> GetClientStatus()
        {
            var result = new List<IMqttClientSessionStatus>();

@@ -78,7 +78,7 @@ namespace MQTTnet.Server
                result.Add(status);
            }

-            return Task.FromResult((IList<IMqttClientSessionStatus>)result);
+            return result;
        }

        public void EnqueueApplicationMessage(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
@@ -52,7 +52,51 @@ namespace MQTTnet.Server

            try
            {
-                await HandleMessageInternalAsync(clientId, applicationMessage).ConfigureAwait(false);
+                List<MqttApplicationMessage> messagesForSave = null;
+                lock (_messages)
+                {
+                    var saveIsRequired = false;
+
+                    if (applicationMessage.Payload?.Length == 0)
+                    {
+                        saveIsRequired = _messages.Remove(applicationMessage.Topic);
+                        _logger.Verbose("Client '{0}' cleared retained message for topic '{1}'.", clientId, applicationMessage.Topic);
+                    }
+                    else
+                    {
+                        if (!_messages.TryGetValue(applicationMessage.Topic, out var existingMessage))
+                        {
+                            _messages[applicationMessage.Topic] = applicationMessage;
+                            saveIsRequired = true;
+                        }
+                        else
+                        {
+                            if (existingMessage.QualityOfServiceLevel != applicationMessage.QualityOfServiceLevel || !existingMessage.Payload.SequenceEqual(applicationMessage.Payload ?? new byte[0]))
+                            {
+                                _messages[applicationMessage.Topic] = applicationMessage;
+                                saveIsRequired = true;
+                            }
+                        }
+
+                        _logger.Verbose("Client '{0}' set retained message for topic '{1}'.", clientId, applicationMessage.Topic);
+                    }
+
+                    if (saveIsRequired)
+                    {
+                        messagesForSave = new List<MqttApplicationMessage>(_messages.Values);
+                    }
+                }
+
+                if (messagesForSave == null)
+                {
+                    _logger.Verbose("Skipped saving retained messages because no changes were detected.");
+                    return;
+                }
+
+                if (_options.Storage != null)
+                {
+                    await _options.Storage.SaveRetainedMessagesAsync(messagesForSave).ConfigureAwait(false);
+                }
            }
            catch (Exception exception)
            {
@@ -84,52 +128,27 @@ namespace MQTTnet.Server
            return retainedMessages;
        }

-        private async Task HandleMessageInternalAsync(string clientId, MqttApplicationMessage applicationMessage)
+        public IList<MqttApplicationMessage> GetMessages()
        {
-            var saveIsRequired = false;
-
            lock (_messages)
            {
-                if (applicationMessage.Payload?.Length == 0)
-                {
-                    saveIsRequired = _messages.Remove(applicationMessage.Topic);
-                    _logger.Info("Client '{0}' cleared retained message for topic '{1}'.", clientId, applicationMessage.Topic);
-                }
-                else
-                {
-                    if (!_messages.TryGetValue(applicationMessage.Topic, out var existingMessage))
-                    {
-                        _messages[applicationMessage.Topic] = applicationMessage;
-                        saveIsRequired = true;
-                    }
-                    else
-                    {
-                        if (existingMessage.QualityOfServiceLevel != applicationMessage.QualityOfServiceLevel || !existingMessage.Payload.SequenceEqual(applicationMessage.Payload ?? new byte[0]))
-                        {
-                            _messages[applicationMessage.Topic] = applicationMessage;
-                            saveIsRequired = true;
-                        }
-                    }
-
-                    _logger.Info("Client '{0}' set retained message for topic '{1}'.", clientId, applicationMessage.Topic);
-                }
+                return _messages.Values.ToList();
            }
+        }

-            if (!saveIsRequired)
+        public Task ClearMessagesAsync()
+        {
+            lock (_messages)
            {
-                _logger.Verbose("Skipped saving retained messages because no changes were detected.");
+                _messages.Clear();
            }

-            if (saveIsRequired && _options.Storage != null)
+            if (_options.Storage != null)
            {
-                List<MqttApplicationMessage> messages;
-                lock (_messages)
-                {
-                    messages = _messages.Values.ToList();
-                }
-
-                await _options.Storage.SaveRetainedMessagesAsync(messages).ConfigureAwait(false);
+                return _options.Storage.SaveRetainedMessagesAsync(new List<MqttApplicationMessage>());
            }
+
+            return Task.FromResult((object)null);
        }
    }
 }
@@ -41,7 +41,17 @@ namespace MQTTnet.Server

        public Task<IList<IMqttClientSessionStatus>> GetClientSessionsStatusAsync()
        {
-            return _clientSessionsManager.GetClientStatusAsync();
+            return Task.FromResult(_clientSessionsManager.GetClientStatus());
+        }
+
+        public IList<IMqttClientSessionStatus> GetClientSessionsStatus()
+        {
+            return _clientSessionsManager.GetClientStatus();
+        }
+
+        public IList<MqttApplicationMessage> GetRetainedMessages()
+        {
+            return _retainedMessagesManager.GetMessages();
        }

        public Task SubscribeAsync(string clientId, IList<TopicFilter> topicFilters)
@@ -129,6 +139,11 @@ namespace MQTTnet.Server
            }
        }

+        public Task ClearRetainedMessagesAsync()
+        {
+            return _retainedMessagesManager?.ClearMessagesAsync();
+        }
+
        internal void OnClientConnected(string clientId)
        {
            _logger.Info("Client '{0}': Connected.", clientId);
@@ -1,5 +1,6 @@
 using System;
 using System.Net;
+using System.Security.Authentication;

 namespace MQTTnet.Server
 {
@@ -80,6 +81,12 @@ namespace MQTTnet.Server
            return this;
        }

+        public MqttServerOptionsBuilder WithEncryptionSslProtocol(SslProtocols value)
+        {
+            _options.TlsEndpointOptions.SslProtocol = value;
+            return this;
+        }
+
        public MqttServerOptionsBuilder WithoutEncryptedEndpoint()
        {
            _options.TlsEndpointOptions.IsEnabled = false;
@@ -1,4 +1,6 @@
-namespace MQTTnet.Server
+using System.Security.Authentication;
+
+namespace MQTTnet.Server
 {
    public class MqttServerTlsTcpEndpointOptions : MqttServerTcpEndpointBaseOptions
    {
@@ -8,5 +10,8 @@
        }

        public byte[] Certificate { get; set; }
+
+
+        public SslProtocols SslProtocol { get; set; } = SslProtocols.Tls12;
    }
 }
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
@@ -7,9 +7,9 @@
  </PropertyGroup>

  <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.7.0" />
-    <PackageReference Include="MSTest.TestAdapter" Version="1.2.1" />
-    <PackageReference Include="MSTest.TestFramework" Version="1.2.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
+    <PackageReference Include="MSTest.TestAdapter" Version="1.3.2" />
+    <PackageReference Include="MSTest.TestFramework" Version="1.3.2" />
  </ItemGroup>

  <ItemGroup>
@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using System.IO.Pipelines;
+using Microsoft.AspNetCore.Connections;
+using Microsoft.AspNetCore.Http.Features;
+
+namespace MQTTnet.AspNetCore.Tests.Mockups
+{
+    public class ConnectionContextMockup : ConnectionContext
+    {
+        public override string ConnectionId { get; set; }
+
+        public override IFeatureCollection Features { get; }
+
+        public override IDictionary<object, object> Items { get; set; }
+        public override IDuplexPipe Transport { get; set; }
+
+        public ConnectionContextMockup()
+        {
+            //Transport = new DefaultConnectionContext
+        }
+    }
+}
@@ -0,0 +1,16 @@
+using System.IO.Pipelines;
+
+namespace MQTTnet.AspNetCore.Tests.Mockups
+{
+    public class DuplexPipeMockup : IDuplexPipe
+    {
+        PipeReader IDuplexPipe.Input => Receive.Reader;
+
+        PipeWriter IDuplexPipe.Output => Send.Writer;
+
+
+        public Pipe Receive { get; set; } = new Pipe();
+
+        public Pipe Send { get; set; } = new Pipe();
+    }
+}
@@ -0,0 +1,51 @@
+using Microsoft.AspNetCore.Connections;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.AspNetCore.Tests.Mockups;
+using MQTTnet.Exceptions;
+using MQTTnet.Packets;
+using MQTTnet.Serializer;
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.AspNetCore.Tests
+{
+    [TestClass]
+    public class MqttConnectionContextTest
+    {
+        [TestMethod]
+        public async Task TestReceivePacketAsyncThrowsWhenReaderCompleted()
+        {
+            var serializer = new MqttPacketSerializer {};
+            var pipe = new DuplexPipeMockup();
+            var connection = new DefaultConnectionContext();
+            connection.Transport = pipe;
+            var ctx = new MqttConnectionContext(serializer, connection);
+
+            pipe.Receive.Writer.Complete();
+
+            await Assert.ThrowsExceptionAsync<MqttCommunicationException>(() => ctx.ReceivePacketAsync(TimeSpan.FromSeconds(1), CancellationToken.None));
+        }
+        
+        [TestMethod]
+        public async Task TestParallelWrites()
+        {
+            var serializer = new MqttPacketSerializer { };
+            var pipe = new DuplexPipeMockup();
+            var connection = new DefaultConnectionContext();
+            connection.Transport = pipe;
+            var ctx = new MqttConnectionContext(serializer, connection);
+
+            var tasks = Enumerable.Range(1, 10).Select(_ => Task.Run(async () => 
+            {
+                for (int i = 0; i < 100; i++)
+                {
+                    await ctx.SendPacketAsync(new MqttPublishPacket(), CancellationToken.None).ConfigureAwait(false);
+                }
+            }));
+
+            await Task.WhenAll(tasks).ConfigureAwait(false);
+        }
+    }
+}
@@ -1,6 +1,4 @@
 using BenchmarkDotNet.Attributes;
-using BenchmarkDotNet.Attributes.Exporters;
-using BenchmarkDotNet.Attributes.Jobs;
 using MQTTnet.Diagnostics;

 namespace MQTTnet.Benchmarks
@@ -8,9 +8,9 @@
  </PropertyGroup>

  <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.10.14" />
-    <PackageReference Include="System.IO.Pipelines" Version="4.5.0" />
-    <PackageReference Include="Microsoft.AspNetCore" Version="2.1.0" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.11.1" />
+    <PackageReference Include="System.IO.Pipelines" Version="4.5.2" />
+    <PackageReference Include="Microsoft.AspNetCore" Version="2.1.4" />
  </ItemGroup>

  <ItemGroup>
@@ -1,7 +1,4 @@
 using BenchmarkDotNet.Attributes;
-using BenchmarkDotNet.Attributes.Columns;
-using BenchmarkDotNet.Attributes.Exporters;
-using BenchmarkDotNet.Attributes.Jobs;
 using MQTTnet.Client;
 using MQTTnet.Server;

@@ -2,8 +2,6 @@
 using MQTTnet.Packets;
 using MQTTnet.Serializer;
 using MQTTnet.Internal;
-using BenchmarkDotNet.Attributes.Jobs;
-using BenchmarkDotNet.Attributes.Exporters;
 using System;
 using System.Threading;
 using System.Threading.Tasks;
@@ -1,6 +1,4 @@
 using BenchmarkDotNet.Attributes;
-using BenchmarkDotNet.Attributes.Exporters;
-using BenchmarkDotNet.Attributes.Jobs;
 using MQTTnet.Server;
 using System;

@@ -0,0 +1,108 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Internal;
+
+namespace MQTTnet.Core.Tests
+{
+    [TestClass]
+    public class BlockingQueueTests
+    {
+        [TestMethod]
+        public void Preserve_Order()
+        {
+            var queue = new BlockingQueue<string>();
+            queue.Enqueue("a");
+            queue.Enqueue("b");
+            queue.Enqueue("c");
+
+            Assert.AreEqual(3, queue.Count);
+
+            Assert.AreEqual("a", queue.Dequeue());
+            Assert.AreEqual("b", queue.Dequeue());
+            Assert.AreEqual("c", queue.Dequeue());
+        }
+
+        [TestMethod]
+        public void Remove_First_Items()
+        {
+            var queue = new BlockingQueue<string>();
+            queue.Enqueue("a");
+            queue.Enqueue("b");
+            queue.Enqueue("c");
+
+            Assert.AreEqual("a", queue.RemoveFirst());
+            Assert.AreEqual("b", queue.RemoveFirst());
+            
+            Assert.AreEqual(1, queue.Count);
+
+            Assert.AreEqual("c", queue.Dequeue());
+        }
+
+        [TestMethod]
+        public void Clear_Items()
+        {
+            var queue = new BlockingQueue<string>();
+            queue.Enqueue("a");
+            queue.Enqueue("b");
+            queue.Enqueue("c");
+
+            Assert.AreEqual(3, queue.Count);
+
+            queue.Clear();
+
+            Assert.AreEqual(0, queue.Count);
+        }
+
+        [TestMethod]
+        public async Task Wait_For_Item()
+        {
+            var queue = new BlockingQueue<string>();
+
+            string item = null;
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            Task.Run(() =>
+            {
+                item = queue.Dequeue();
+            });
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+
+            await Task.Delay(100);
+
+            Assert.AreEqual(0, queue.Count);
+            Assert.AreEqual(null, item);
+
+            queue.Enqueue("x");
+
+            await Task.Delay(100);
+
+            Assert.AreEqual("x", item);
+            Assert.AreEqual(0, queue.Count);
+        }
+
+        [TestMethod]
+        public void Wait_For_Times()
+        {
+            var number = 0;
+
+            var queue = new BlockingQueue<int>();
+
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            Task.Run(async () =>
+            {
+                while (true)
+                {
+                    queue.Enqueue(1);
+                    await Task.Delay(100);
+                }
+            });
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+
+            while (number < 50)
+            {
+                queue.Dequeue();
+                Interlocked.Increment(ref number);
+            }
+        }
+    }
+}
@@ -3,16 +3,17 @@
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <DebugType>Full</DebugType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="MSTest.TestAdapter" Version="1.3.2" />
    <PackageReference Include="MSTest.TestFramework" Version="1.3.2" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.7.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
  </ItemGroup>

  <ItemGroup>
+    <ProjectReference Include="..\..\Source\MQTTnet.Extensions.ManagedClient\MQTTnet.Extensions.ManagedClient.csproj" />
    <ProjectReference Include="..\..\Source\MQTTnet\MQTTnet.csproj" />
  </ItemGroup>

@@ -0,0 +1,38 @@
+using MQTTnet.Extensions.ManagedClient;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Server;
+
+namespace MQTTnet.Core.Tests
+{
+    [TestClass]
+    public class ManagedMqttClientTests
+    {
+        [TestMethod]
+        public async Task Drop_New_Messages_On_Full_Queue()
+        {
+            var factory = new MqttFactory();
+            var managedClient = factory.CreateManagedMqttClient();
+
+            var clientOptions = new ManagedMqttClientOptionsBuilder()
+                .WithMaxPendingMessages(5)
+                .WithPendingMessagesOverflowStrategy(MqttPendingMessagesOverflowStrategy.DropNewMessage);
+
+            clientOptions.WithClientOptions(o => o.WithTcpServer("localhost"));
+
+            await managedClient.StartAsync(clientOptions.Build());
+
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "1" });
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "2" });
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "3" });
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "4" });
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "5" });
+
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "6" });
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "7" });
+            await managedClient.PublishAsync(new MqttApplicationMessage { Topic = "8" });
+
+            Assert.AreEqual(5, managedClient.PendingApplicationMessagesCount);
+        }
+    }
+}
@@ -5,9 +5,11 @@ using MQTTnet.Protocol;
 using MQTTnet.Server;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using MQTTnet.Adapter;
 using MQTTnet.Implementations;

 namespace MQTTnet.Core.Tests
@@ -97,11 +99,11 @@ namespace MQTTnet.Core.Tests
                c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;

                var message = new MqttApplicationMessageBuilder().WithTopic("a").WithAtLeastOnceQoS().Build();
-                
+
                await c2.PublishAsync(message);
                await Task.Delay(1000);
                Assert.AreEqual(0, receivedMessagesCount);
-                
+
                var subscribeEventCalled = false;
                s.ClientSubscribedTopic += (_, e) =>
                    {
@@ -115,7 +117,7 @@ namespace MQTTnet.Core.Tests
                await c2.PublishAsync(message);
                await Task.Delay(500);
                Assert.AreEqual(1, receivedMessagesCount);
-                
+
                var unsubscribeEventCalled = false;
                s.ClientUnsubscribedTopic += (_, e) =>
                {
@@ -233,7 +235,7 @@ namespace MQTTnet.Core.Tests
                await c1.PublishAsync(message);
            }
        }
-        
+
        [TestMethod]
        public async Task MqttServer_ShutdownDisconnectsClientsGracefully()
        {
@@ -302,6 +304,59 @@ namespace MQTTnet.Core.Tests
            Assert.AreEqual(clientConnectedCalled, clientDisconnectedCalled);
        }

+        [TestMethod]
+        public async Task MqttServer_LotsOfRetainedMessages()
+        {
+            const int ClientCount = 100;
+
+            var server = new MqttFactory().CreateMqttServer();
+            try
+            {
+                await server.StartAsync(new MqttServerOptionsBuilder().Build());
+
+                Parallel.For(
+                    0,
+                    ClientCount,
+                    new ParallelOptions { MaxDegreeOfParallelism = 10 },
+                    i =>
+                {
+                    using (var client = new MqttFactory().CreateMqttClient())
+                    {
+                        client.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build())
+                            .GetAwaiter().GetResult();
+
+                        for (var j = 0; j < 10; j++)
+                        {
+                            // Clear retained message.
+                            client.PublishAsync(new MqttApplicationMessageBuilder().WithTopic("r" + i)
+                                .WithPayload(new byte[0]).WithRetainFlag().Build()).GetAwaiter().GetResult();
+
+                            // Set retained message.
+                            client.PublishAsync(new MqttApplicationMessageBuilder().WithTopic("r" + i)
+                                .WithPayload("value" + j).WithRetainFlag().Build()).GetAwaiter().GetResult();
+                        }
+
+                        client.DisconnectAsync().GetAwaiter().GetResult();
+                    }
+                });
+
+                await Task.Delay(100);
+
+                var retainedMessages = server.GetRetainedMessages();
+
+                Assert.AreEqual(ClientCount, retainedMessages.Count);
+
+                for (var i = 0; i < ClientCount; i++)
+                {
+                    Assert.IsTrue(retainedMessages.Any(m => m.Topic == "r" + i));
+                }
+            }
+            finally
+            {
+                await server.StopAsync();
+            }
+        }
+
        [TestMethod]
        public async Task MqttServer_RetainedMessagesFlow()
        {
@@ -552,6 +607,51 @@ namespace MQTTnet.Core.Tests
            Assert.IsTrue(bodyIsMatching);
        }

+        [TestMethod]
+        public async Task MqttServer_ConnectionDenied()
+        {
+            var server = new MqttFactory().CreateMqttServer();
+            var client = new MqttFactory().CreateMqttClient();
+
+            try
+            {
+                var options = new MqttServerOptionsBuilder().WithConnectionValidator(context =>
+                {
+                    context.ReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized;
+                }).Build();
+
+                await server.StartAsync(options);
+
+
+                var clientOptions = new MqttClientOptionsBuilder()
+                    .WithTcpServer("localhost").Build();
+
+                try
+                {
+                    await client.ConnectAsync(clientOptions);
+                    Assert.Fail("An exception should be raised.");
+                }
+                catch (Exception exception)
+                {
+                    if (exception is MqttConnectingFailedException)
+                    {
+
+                    }
+                    else
+                    {
+                        Assert.Fail("Wrong exception.");
+                    }
+                }
+            }
+            finally
+            {
+                await client.DisconnectAsync();
+                await server.StopAsync();
+
+                client.Dispose();
+            }
+        }
+
        [TestMethod]
        public async Task MqttServer_SameClientIdConnectDisconnectEventOrder()
        {
@@ -600,6 +700,33 @@ namespace MQTTnet.Core.Tests
            Assert.IsFalse(connecteCalledBeforeConnectedClients, "ClientConnected was called before ClientDisconnect was called");
        }

+
+        [TestMethod]
+        public async Task MqttServer_StopAndRestart()
+        {
+            var server = new MqttFactory().CreateMqttServer();
+            await server.StartAsync(new MqttServerOptions());
+
+            var client = new MqttFactory().CreateMqttClient();
+            await client.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
+            await server.StopAsync();
+
+            try
+            {
+                var client2 = new MqttFactory().CreateMqttClient();
+                await client2.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
+
+                Assert.Fail("Connecting should fail.");
+            }
+            catch (Exception)
+            {
+            }
+
+            await server.StartAsync(new MqttServerOptions());
+            var client3 = new MqttFactory().CreateMqttClient();
+            await client3.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
+        }
+
        private class TestStorage : IMqttServerStorage
        {
            public IList<MqttApplicationMessage> Messages = new List<MqttApplicationMessage>();
@@ -623,25 +750,24 @@ namespace MQTTnet.Core.Tests
            MqttQualityOfServiceLevel filterQualityOfServiceLevel,
            int expectedReceivedMessagesCount)
        {
-            var serverAdapter = new TestMqttServerAdapter();
-            var s = new MqttFactory().CreateMqttServer(new[] { serverAdapter }, new MqttNetLogger());
+            var s = new MqttFactory().CreateMqttServer();

            var receivedMessagesCount = 0;
            try
            {
                await s.StartAsync(new MqttServerOptions());

-                var c1 = await serverAdapter.ConnectTestClient("c1");
-                var c2 = await serverAdapter.ConnectTestClient("c2");
-
+                var c1 = new MqttFactory().CreateMqttClient();
                c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
-
+                await c1.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
                await c1.SubscribeAsync(new TopicFilterBuilder().WithTopic(topicFilter).WithQualityOfServiceLevel(filterQualityOfServiceLevel).Build());
+
+                var c2 = new MqttFactory().CreateMqttClient();
+                await c2.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
                await c2.PublishAsync(builder => builder.WithTopic(topic).WithPayload(new byte[0]).WithQualityOfServiceLevel(qualityOfServiceLevel));

                await Task.Delay(500);
                await c1.UnsubscribeAsync(topicFilter);
-
                await Task.Delay(500);
            }
            finally
@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Client;
+using MQTTnet.Server;
+
+namespace MQTTnet.Core.Tests
+{
+    [TestClass]
+    public class RoundtripTimeTests
+    {
+        [TestMethod]
+        public async Task Round_Trip_Time()
+        {
+            var factory = new MqttFactory();
+            var server = factory.CreateMqttServer();
+            var receiverClient = factory.CreateMqttClient();
+            var senderClient = factory.CreateMqttClient();
+
+            await server.StartAsync(new MqttServerOptionsBuilder().Build());
+
+            await receiverClient.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
+            await receiverClient.SubscribeAsync("#");
+
+            await senderClient.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("localhost").Build());
+
+            TaskCompletionSource<string> response = null;
+
+            receiverClient.ApplicationMessageReceived += (sender, args) =>
+            {
+                response?.SetResult(args.ApplicationMessage.ConvertPayloadToString());
+            };
+
+            var times = new List<TimeSpan>();
+            var stopwatch = Stopwatch.StartNew();
+
+            for (var i = 0; i < 100; i++)
+            {
+                response = new TaskCompletionSource<string>();
+                await senderClient.PublishAsync("test", DateTime.UtcNow.Ticks.ToString());
+                response.Task.GetAwaiter().GetResult();
+
+                stopwatch.Stop();
+                times.Add(stopwatch.Elapsed);
+                stopwatch.Restart();
+            }
+
+            await server.StopAsync();
+        }
+    }
+}
@@ -11,19 +11,20 @@ namespace MQTTnet.Core.Tests
        /// publishes a message with a client and waits in the server until a message with the same topic is received
        /// </summary>
        /// <returns></returns>
-        public static async Task PublishAndWaitForAsync(this IMqttClient client, IMqttServer server, MqttApplicationMessage message) 
+        public static async Task PublishAndWaitForAsync(this IMqttClient client, IMqttServer server, MqttApplicationMessage message)
        {
            var tcs = new TaskCompletionSource<object>();

-            EventHandler<MqttApplicationMessageReceivedEventArgs> handler = (sender, args) =>
+            void Handler(object sender, MqttApplicationMessageReceivedEventArgs args)
            {
                if (args.ApplicationMessage.Topic == message.Topic)
                {
                    tcs.SetResult(true);
                }
-            };
-            server.ApplicationMessageReceived += handler;
-            
+            }
+
+            server.ApplicationMessageReceived += Handler;
+
            try
            {
                await client.PublishAsync(message).ConfigureAwait(false);
@@ -31,7 +32,7 @@ namespace MQTTnet.Core.Tests
            }
            finally
            {
-                server.ApplicationMessageReceived -= handler;
+                server.ApplicationMessageReceived -= Handler;
            }
        }
    }
@@ -10,8 +10,10 @@
  </ItemGroup>

  <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore" Version="2.1.0" />
-    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.0" />
+    <PackageReference Include="Microsoft.AspNetCore" Version="2.1.4" />
+    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.5" />
+    <PackageReference Include="Microsoft.AspNetCore.Connections.Abstractions" Version="2.1.3" />
+    <PackageReference Include="Microsoft.AspNetCore.Http.Abstractions" Version="2.1.1" />
  </ItemGroup>

  <ItemGroup>
@@ -3,11 +3,11 @@
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <DebugType>Full</DebugType>
-    <TargetFrameworks>netcoreapp2.0;net452;net461</TargetFrameworks>
+    <TargetFrameworks>netcoreapp2.1;net452;net461</TargetFrameworks>
  </PropertyGroup>

-  <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Release|netcoreapp2.0|AnyCPU'">
-    <DefineConstants>RELEASE;NETCOREAPP2_0</DefineConstants>
+  <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Release|netcoreapp2.1|AnyCPU'">
+    <DefineConstants>RELEASE;NETCOREAPP2_1</DefineConstants>
  </PropertyGroup>

  <ItemGroup>
@@ -142,10 +142,10 @@
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
-      <Version>6.1.5</Version>
+      <Version>6.1.9</Version>
    </PackageReference>
    <PackageReference Include="Microsoft.Toolkit.Uwp.UI.Controls">
-      <Version>3.0.0</Version>
+      <Version>4.0.0</Version>
    </PackageReference>
  </ItemGroup>
  <PropertyGroup Condition=" '$(VisualStudioVersion)' == '' or '$(VisualStudioVersion)' &lt; '14.0' ">