diff --git a/Frameworks/MQTTnet.NetStandard/Implementations/MqttCommunicationAdapterFactory.cs b/Frameworks/MQTTnet.NetStandard/Implementations/MqttCommunicationAdapterFactory.cs
index 799ccdd..05e6fb6 100644
--- a/Frameworks/MQTTnet.NetStandard/Implementations/MqttCommunicationAdapterFactory.cs
+++ b/Frameworks/MQTTnet.NetStandard/Implementations/MqttCommunicationAdapterFactory.cs
@@ -7,7 +7,7 @@ namespace MQTTnet.Implementations
 {
     public class MqttCommunicationAdapterFactory : IMqttCommunicationAdapterFactory
     {
-        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(IMqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
diff --git a/Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs b/Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs
index dfe3654..cd9151e 100644
--- a/Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs
+++ b/Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs
@@ -48,8 +48,7 @@ namespace MQTTnet.Implementations
         public Stream SendStream { get; private set; }
         public Stream ReceiveStream { get; private set; }
         public Stream RawReceiveStream { get; private set; }
-
-
+        
         public static Func<X509Certificate, X509Chain, SslPolicyErrors, MqttClientTcpOptions, bool> CustomCertificateValidationCallback { get; set; }
 
         public async Task ConnectAsync()
@@ -121,7 +120,7 @@ namespace MQTTnet.Implementations
             return _options.TlsOptions.AllowUntrustedCertificates;
         }
 
-        private static X509CertificateCollection LoadCertificates(MqttClientOptions options)
+        private static X509CertificateCollection LoadCertificates(IMqttClientOptions options)
         {
             var certificates = new X509CertificateCollection();
             if (options.TlsOptions.Certificates == null)
diff --git a/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttCommunicationAdapterFactory.cs b/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttCommunicationAdapterFactory.cs
index 799ccdd..05e6fb6 100644
--- a/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttCommunicationAdapterFactory.cs
+++ b/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttCommunicationAdapterFactory.cs
@@ -7,7 +7,7 @@ namespace MQTTnet.Implementations
 {
     public class MqttCommunicationAdapterFactory : IMqttCommunicationAdapterFactory
     {
-        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(IMqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
diff --git a/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs b/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs
index 03206f1..1a96f1e 100644
--- a/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs
+++ b/Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs
@@ -89,7 +89,7 @@ namespace MQTTnet.Implementations
             RawReceiveStream = ReceiveStream;
         }
 
-        private static Certificate LoadCertificate(MqttClientOptions options)
+        private static Certificate LoadCertificate(BaseMqttClientOptions options)
         {
             if (options.TlsOptions.Certificates == null || !options.TlsOptions.Certificates.Any())
             {
diff --git a/MQTTnet.Core/Client/MqttClientOptions.cs b/MQTTnet.Core/Client/BaseMqttClientOptions.cs
similarity index 89%
rename from MQTTnet.Core/Client/MqttClientOptions.cs
rename to MQTTnet.Core/Client/BaseMqttClientOptions.cs
index f2e28fb..ca3f82e 100644
--- a/MQTTnet.Core/Client/MqttClientOptions.cs
+++ b/MQTTnet.Core/Client/BaseMqttClientOptions.cs
@@ -3,7 +3,7 @@ using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Client
 {
-    public abstract class MqttClientOptions
+    public abstract class BaseMqttClientOptions : IMqttClientOptions
     {
         public MqttClientTlsOptions TlsOptions { get; set; } = new MqttClientTlsOptions();
 
@@ -13,7 +13,7 @@ namespace MQTTnet.Core.Client
 
         public string Password { get; set; }
 
-        public string ClientId { get; set; } = Guid.NewGuid().ToString().Replace("-", string.Empty);
+        public string ClientId { get; set; } = Guid.NewGuid().ToString("N");
 
         public bool CleanSession { get; set; } = true;
 
diff --git a/MQTTnet.Core/Client/IMqttClient.cs b/MQTTnet.Core/Client/IMqttClient.cs
index 7622867..7219c58 100644
--- a/MQTTnet.Core/Client/IMqttClient.cs
+++ b/MQTTnet.Core/Client/IMqttClient.cs
@@ -11,9 +11,9 @@ namespace MQTTnet.Core.Client
 
         event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
         event EventHandler Connected;
-        event EventHandler Disconnected;
+        event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;
 
-        Task ConnectAsync(MqttClientOptions options);
+        Task ConnectAsync(IMqttClientOptions options);
         Task DisconnectAsync();
 
         Task<IList<MqttSubscribeResult>> SubscribeAsync(IEnumerable<TopicFilter> topicFilters);
diff --git a/MQTTnet.Core/Client/IMqttClientOptions.cs b/MQTTnet.Core/Client/IMqttClientOptions.cs
new file mode 100644
index 0000000..7e675ff
--- /dev/null
+++ b/MQTTnet.Core/Client/IMqttClientOptions.cs
@@ -0,0 +1,18 @@
+using System;
+using MQTTnet.Core.Serializer;
+
+namespace MQTTnet.Core.Client
+{
+    public interface IMqttClientOptions
+    {
+        bool CleanSession { get; }
+        string ClientId { get; }
+        TimeSpan DefaultCommunicationTimeout { get; }
+        TimeSpan KeepAlivePeriod { get; }
+        string Password { get; }
+        MqttProtocolVersion ProtocolVersion { get; }
+        MqttClientTlsOptions TlsOptions { get; }
+        string UserName { get; }
+        MqttApplicationMessage WillMessage { get; }
+    }
+}
\ No newline at end of file
diff --git a/MQTTnet.Core/Client/IMqttCommunicationAdapterFactory.cs b/MQTTnet.Core/Client/IMqttCommunicationAdapterFactory.cs
index 092ea04..0e29590 100644
--- a/MQTTnet.Core/Client/IMqttCommunicationAdapterFactory.cs
+++ b/MQTTnet.Core/Client/IMqttCommunicationAdapterFactory.cs
@@ -4,6 +4,6 @@ namespace MQTTnet.Core.Client
 {
     public interface IMqttCommunicationAdapterFactory
     {
-        IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options);
+        IMqttCommunicationAdapter CreateMqttCommunicationAdapter(IMqttClientOptions options);
     }
 }
\ No newline at end of file
diff --git a/MQTTnet.Core/Client/MqttClient.cs b/MQTTnet.Core/Client/MqttClient.cs
index 80b850a..5385790 100644
--- a/MQTTnet.Core/Client/MqttClient.cs
+++ b/MQTTnet.Core/Client/MqttClient.cs
@@ -18,7 +18,7 @@ namespace MQTTnet.Core.Client
         private readonly MqttPacketDispatcher _packetDispatcher = new MqttPacketDispatcher();
         private readonly IMqttCommunicationAdapterFactory _communicationChannelFactory;
 
-        private MqttClientOptions _options;
+        private IMqttClientOptions _options;
         private bool _isReceivingPackets;
         private int _latestPacketIdentifier;
         private CancellationTokenSource _cancellationTokenSource;
@@ -30,12 +30,12 @@ namespace MQTTnet.Core.Client
         }
 
         public event EventHandler Connected;
-        public event EventHandler Disconnected;
+        public event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;
         public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
 
-        public bool IsConnected => _cancellationTokenSource != null && !_cancellationTokenSource.IsCancellationRequested;
+        public bool IsConnected { get; private set; }
 
-        public async Task ConnectAsync(MqttClientOptions options)
+        public async Task ConnectAsync(IMqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
@@ -64,6 +64,7 @@ namespace MQTTnet.Core.Client
                     StartSendKeepAliveMessages(_cancellationTokenSource.Token);
                 }
 
+                IsConnected = true;
                 Connected?.Invoke(this, EventArgs.Empty);
             }
             catch (Exception)
@@ -222,6 +223,9 @@ namespace MQTTnet.Core.Client
 
         private async Task DisconnectInternalAsync()
         {
+            var clientWasConnected = IsConnected;
+            IsConnected = false;
+
             var cts = _cancellationTokenSource;
             if (cts == null || cts.IsCancellationRequested)
             {
@@ -243,7 +247,7 @@ namespace MQTTnet.Core.Client
             }
             finally
             {
-                Disconnected?.Invoke(this, EventArgs.Empty);
+                Disconnected?.Invoke(this, new MqttClientDisconnectedEventArgs(clientWasConnected));
             }
         }
 
diff --git a/MQTTnet.Core/Client/MqttClientDisconnectedEventArgs.cs b/MQTTnet.Core/Client/MqttClientDisconnectedEventArgs.cs
new file mode 100644
index 0000000..1e9609e
--- /dev/null
+++ b/MQTTnet.Core/Client/MqttClientDisconnectedEventArgs.cs
@@ -0,0 +1,14 @@
+using System;
+
+namespace MQTTnet.Core.Client
+{
+    public class MqttClientDisconnectedEventArgs : EventArgs
+    {
+        public MqttClientDisconnectedEventArgs(bool clientWasConnected)
+        {
+            ClientWasConnected = clientWasConnected;
+        }
+
+        public bool ClientWasConnected { get; }
+    }
+}
diff --git a/MQTTnet.Core/Client/MqttClientTcpOptions.cs b/MQTTnet.Core/Client/MqttClientTcpOptions.cs
index beaa506..51d2b97 100644
--- a/MQTTnet.Core/Client/MqttClientTcpOptions.cs
+++ b/MQTTnet.Core/Client/MqttClientTcpOptions.cs
@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Client
 {
-    public class MqttClientTcpOptions : MqttClientOptions
+    public class MqttClientTcpOptions : BaseMqttClientOptions
     {
         public string Server { get; set; }
 
diff --git a/MQTTnet.Core/Client/MqttClientWebSocketOptions.cs b/MQTTnet.Core/Client/MqttClientWebSocketOptions.cs
index 4b90524..b2b5777 100644
--- a/MQTTnet.Core/Client/MqttClientWebSocketOptions.cs
+++ b/MQTTnet.Core/Client/MqttClientWebSocketOptions.cs
@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Client
 {
-    public class MqttClientWebSocketOptions : MqttClientOptions
+    public class MqttClientWebSocketOptions : BaseMqttClientOptions
     {
         public string Uri { get; set; }
     }
diff --git a/MQTTnet.Core/Exceptions/MqttCommunicationException.cs b/MQTTnet.Core/Exceptions/MqttCommunicationException.cs
index 2fc578e..e019f4e 100644
--- a/MQTTnet.Core/Exceptions/MqttCommunicationException.cs
+++ b/MQTTnet.Core/Exceptions/MqttCommunicationException.cs
@@ -17,10 +17,5 @@ namespace MQTTnet.Core.Exceptions
             : base(message)
         {
         }
-
-        public MqttCommunicationException(string message, Exception innerException)
-            : base(message, innerException)
-        {
-        }
     }
 }
diff --git a/MQTTnet.Core/MQTTnet.Core.csproj b/MQTTnet.Core/MQTTnet.Core.csproj
index 0e9b965..679e4a8 100644
--- a/MQTTnet.Core/MQTTnet.Core.csproj
+++ b/MQTTnet.Core/MQTTnet.Core.csproj
@@ -32,4 +32,8 @@
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Any CPU|x86'" />
 
+  <ItemGroup>
+    <Folder Include="ManagedClient\" />
+  </ItemGroup>
+
 </Project>
\ No newline at end of file
diff --git a/MQTTnet.Core/MqttApplicationMessageFactory.cs b/MQTTnet.Core/MqttApplicationMessageFactory.cs
index 55025a3..c5bbee5 100644
--- a/MQTTnet.Core/MqttApplicationMessageFactory.cs
+++ b/MQTTnet.Core/MqttApplicationMessageFactory.cs
@@ -8,13 +8,6 @@ namespace MQTTnet.Core
 {
     public class MqttApplicationMessageFactory
     {
-        public MqttApplicationMessage CreateApplicationMessage(string topic, MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce, bool retain = false)
-        {
-            if (topic == null) throw new ArgumentNullException(nameof(topic));
-
-            return CreateApplicationMessage(topic, new byte[0], qualityOfServiceLevel, retain);
-        }
-
         public MqttApplicationMessage CreateApplicationMessage(string topic, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce, bool retain = false)
         {
             if (topic == null) throw new ArgumentNullException(nameof(topic));
diff --git a/MQTTnet.Core/Packets/MqttPacketExtensions.cs b/MQTTnet.Core/Packets/MqttPacketExtensions.cs
index fef1054..6a7e0ce 100644
--- a/MQTTnet.Core/Packets/MqttPacketExtensions.cs
+++ b/MQTTnet.Core/Packets/MqttPacketExtensions.cs
@@ -12,8 +12,7 @@ namespace MQTTnet.Core.Packets
 
             if (responsePacket is IMqttPacketWithIdentifier responsePacketWithIdentifier)
             {
-                var requestPacketWithIdentifier = packet as IMqttPacketWithIdentifier;
-                if (requestPacketWithIdentifier == null)
+                if (!(packet is IMqttPacketWithIdentifier requestPacketWithIdentifier))
                 {
                     throw new InvalidOperationException("Response packet has PacketIdentifier but request packet does not.");
                 }
diff --git a/MQTTnet.Core/Packets/MqttSubAckPacket.cs b/MQTTnet.Core/Packets/MqttSubAckPacket.cs
index ee577ae..5882d4c 100644
--- a/MQTTnet.Core/Packets/MqttSubAckPacket.cs
+++ b/MQTTnet.Core/Packets/MqttSubAckPacket.cs
@@ -8,7 +8,7 @@ namespace MQTTnet.Core.Packets
     {
         public ushort PacketIdentifier { get; set; }
 
-        public IList<MqttSubscribeReturnCode> SubscribeReturnCodes { get; set; } = new List<MqttSubscribeReturnCode>();
+        public IList<MqttSubscribeReturnCode> SubscribeReturnCodes { get; } = new List<MqttSubscribeReturnCode>();
 
         public override string ToString()
         {
diff --git a/MQTTnet.Core/Serializer/MqttPacketSerializer.cs b/MQTTnet.Core/Serializer/MqttPacketSerializer.cs
index d31a8fe..833d798 100644
--- a/MQTTnet.Core/Serializer/MqttPacketSerializer.cs
+++ b/MQTTnet.Core/Serializer/MqttPacketSerializer.cs
@@ -58,19 +58,19 @@ namespace MQTTnet.Core.Serializer
                 return Serialize(connAckPacket, writer);
             }
 
-            if (packet is MqttDisconnectPacket disconnectPacket)
+            if (packet is MqttDisconnectPacket)
             {
-                return Serialize(disconnectPacket);
+                return SerializeEmptyPacket(MqttControlPacketType.Disconnect);
             }
 
-            if (packet is MqttPingReqPacket pingReqPacket)
+            if (packet is MqttPingReqPacket)
             {
-                return Serialize(pingReqPacket);
+                return SerializeEmptyPacket(MqttControlPacketType.PingReq);
             }
 
-            if (packet is MqttPingRespPacket pingRespPacket)
+            if (packet is MqttPingRespPacket)
             {
-                return Serialize(pingRespPacket);
+                return SerializeEmptyPacket(MqttControlPacketType.PingResp);
             }
 
             if (packet is MqttPublishPacket publishPacket)
@@ -338,6 +338,8 @@ namespace MQTTnet.Core.Serializer
 
         private static void ValidateConnectPacket(MqttConnectPacket packet)
         {
+            if (packet == null) throw new ArgumentNullException(nameof(packet));
+
             if (string.IsNullOrEmpty(packet.ClientId) && !packet.CleanSession)
             {
                 throw new MqttProtocolViolationException("CleanSession must be set if ClientId is empty [MQTT-3.1.3-7].");
@@ -346,6 +348,8 @@ namespace MQTTnet.Core.Serializer
 
         private static void ValidatePublishPacket(MqttPublishPacket packet)
         {
+            if (packet == null) throw new ArgumentNullException(nameof(packet));
+
             if (packet.QualityOfServiceLevel == 0 && packet.Dup)
             {
                 throw new MqttProtocolViolationException("Dup flag must be false for QoS 0 packets [MQTT-3.3.1-2].");
@@ -433,21 +437,6 @@ namespace MQTTnet.Core.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubRel, 0x02);
         }
 
-        private static byte Serialize(MqttDisconnectPacket packet)
-        {
-            return SerializeEmptyPacket(MqttControlPacketType.Disconnect);
-        }
-
-        private static byte Serialize(MqttPingReqPacket packet)
-        {
-            return SerializeEmptyPacket(MqttControlPacketType.PingReq);
-        }
-
-        private static byte Serialize(MqttPingRespPacket packet)
-        {
-            return SerializeEmptyPacket(MqttControlPacketType.PingResp);
-        }
-
         private static byte Serialize(MqttPublishPacket packet, MqttPacketWriter writer)
         {
             ValidatePublishPacket(packet);
diff --git a/MQTTnet.Core/Server/IMqttServer.cs b/MQTTnet.Core/Server/IMqttServer.cs
index 023feb8..a35a266 100644
--- a/MQTTnet.Core/Server/IMqttServer.cs
+++ b/MQTTnet.Core/Server/IMqttServer.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
-using MQTTnet.Core.Adapter;
 
 namespace MQTTnet.Core.Server
 {
@@ -11,7 +10,7 @@ namespace MQTTnet.Core.Server
         event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
         event EventHandler<MqttClientDisconnectedEventArgs> ClientDisconnected;
 
-        IReadOnlyList<ConnectedMqttClient> GetConnectedClients();
+        IList<ConnectedMqttClient> GetConnectedClients();
         void Publish(MqttApplicationMessage applicationMessage);
 
         Task StartAsync();
diff --git a/MQTTnet.Core/Server/MqttClientSessionsManager.cs b/MQTTnet.Core/Server/MqttClientSessionsManager.cs
index f78a541..9c9fbfd 100644
--- a/MQTTnet.Core/Server/MqttClientSessionsManager.cs
+++ b/MQTTnet.Core/Server/MqttClientSessionsManager.cs
@@ -103,7 +103,7 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        public IReadOnlyList<ConnectedMqttClient> GetConnectedClients()
+        public IList<ConnectedMqttClient> GetConnectedClients()
         {
             lock (_clientSessions)
             {
diff --git a/MQTTnet.Core/Server/MqttServer.cs b/MQTTnet.Core/Server/MqttServer.cs
index d6f2379..d1615d8 100644
--- a/MQTTnet.Core/Server/MqttServer.cs
+++ b/MQTTnet.Core/Server/MqttServer.cs
@@ -27,7 +27,7 @@ namespace MQTTnet.Core.Server
             _clientSessionsManager.ClientDisconnected += OnClientDisconnected;
         }
 
-        public IReadOnlyList<ConnectedMqttClient> GetConnectedClients()
+        public IList<ConnectedMqttClient> GetConnectedClients()
         {
             return _clientSessionsManager.GetConnectedClients();
         }
diff --git a/Tests/MQTTnet.Core.Tests/ExtensionTests.cs b/Tests/MQTTnet.Core.Tests/ExtensionTests.cs
index 2564e69..2f0966f 100644
--- a/Tests/MQTTnet.Core.Tests/ExtensionTests.cs
+++ b/Tests/MQTTnet.Core.Tests/ExtensionTests.cs
@@ -55,7 +55,7 @@ namespace MQTTnet.Core.Tests
         {
             try
             {
-                var r = await Task.Run(() =>
+                await Task.Run(() =>
                 {
                     var iis = new int[0];
                     return iis[1];
diff --git a/Tests/MQTTnet.Core.Tests/MqttApplicationMessageFactoryTests.cs b/Tests/MQTTnet.Core.Tests/MqttApplicationMessageFactoryTests.cs
new file mode 100644
index 0000000..f0f464a
--- /dev/null
+++ b/Tests/MQTTnet.Core.Tests/MqttApplicationMessageFactoryTests.cs
@@ -0,0 +1,30 @@
+using System;
+using System.Text;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Core.Protocol;
+
+namespace MQTTnet.Core.Tests
+{
+    [TestClass]
+    public class MqttApplicationMessageFactoryTests
+    {
+        [TestMethod]
+        public void CreateApplicationMessage_TopicOnly()
+        {
+            var message = new MqttApplicationMessageFactory().CreateApplicationMessage("Abc", MqttQualityOfServiceLevel.AtLeastOnce);
+            Assert.AreEqual("Abc", message.Topic);
+            Assert.IsFalse(message.Retain);
+            Assert.AreEqual(MqttQualityOfServiceLevel.AtLeastOnce, message.QualityOfServiceLevel);
+        }
+
+        [TestMethod]
+        public void CreateApplicationMessage_TimeStampPayload()
+        {
+            var message = new MqttApplicationMessageFactory().CreateApplicationMessage("xyz", TimeSpan.FromSeconds(360));
+            Assert.AreEqual("xyz", message.Topic);
+            Assert.IsFalse(message.Retain);
+            Assert.AreEqual(MqttQualityOfServiceLevel.AtMostOnce, message.QualityOfServiceLevel);
+            Assert.AreEqual(Encoding.UTF8.GetString(message.Payload), "00:06:00");
+        }
+    }
+}
diff --git a/Tests/MQTTnet.Core.Tests/MqttCommunicationAdapterFactory.cs b/Tests/MQTTnet.Core.Tests/MqttCommunicationAdapterFactory.cs
index c83f83a..bed3218 100644
--- a/Tests/MQTTnet.Core.Tests/MqttCommunicationAdapterFactory.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttCommunicationAdapterFactory.cs
@@ -12,7 +12,7 @@ namespace MQTTnet.Core.Tests
             _adapter = adapter;
         }
 
-        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(IMqttClientOptions options)
         {
             return _adapter;
         }
diff --git a/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs b/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
index de6265f..c78e3ae 100644
--- a/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
@@ -2,10 +2,8 @@
 using System.IO;
 using System.Text;
 using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Channel;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
 using MQTTnet.Core.Serializer;
@@ -387,45 +385,6 @@ namespace MQTTnet.Core.Tests
             DeserializeAndCompare(p, "sAIAew==");
         }
 
-
-        public class TestChannel : IMqttCommunicationChannel
-        {
-            private readonly MemoryStream _stream = new MemoryStream();
-
-            public Stream ReceiveStream => _stream;
-
-            public Stream RawReceiveStream => _stream;
-
-            public Stream SendStream => _stream;
-
-            public bool IsConnected { get; } = true;
-
-            public TestChannel()
-            {
-            }
-
-            public TestChannel(byte[] initialData)
-            {
-                _stream.Write(initialData, 0, initialData.Length);
-                _stream.Position = 0;
-            }
-
-            public Task ConnectAsync()
-            {
-                return Task.FromResult(0);
-            }
-
-            public Task DisconnectAsync()
-            {
-                return Task.FromResult(0);
-            }
-
-            public byte[] ToArray()
-            {
-                return _stream.ToArray();
-            }
-        }
-
         private static void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
             var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
diff --git a/Tests/MQTTnet.TestApp.NetCore/MQTTnet.TestApp.NetCore.csproj b/Tests/MQTTnet.TestApp.NetCore/MQTTnet.TestApp.NetCore.csproj
index 867b013..41ece1b 100644
--- a/Tests/MQTTnet.TestApp.NetCore/MQTTnet.TestApp.NetCore.csproj
+++ b/Tests/MQTTnet.TestApp.NetCore/MQTTnet.TestApp.NetCore.csproj
@@ -6,6 +6,10 @@
     <TargetFrameworks>netcoreapp2.0;net45</TargetFrameworks>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\..\Frameworks\MQTTnet.Netstandard\MQTTnet.NetStandard.csproj" />
     <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj" />
diff --git a/Tests/MQTTnet.TestApp.NetCore/PerformanceTest.cs b/Tests/MQTTnet.TestApp.NetCore/PerformanceTest.cs
index d7060f2..f8b8c33 100644
--- a/Tests/MQTTnet.TestApp.NetCore/PerformanceTest.cs
+++ b/Tests/MQTTnet.TestApp.NetCore/PerformanceTest.cs
@@ -113,7 +113,8 @@ namespace MQTTnet.TestApp.NetCore
                         .Select(i => CreateMessage())
                         .ToList();
 
-                    if (true)
+                    Console.WriteLine("Press 'c' for concurrent sends. Otherwise in one batch.");
+                    if (Console.ReadKey().KeyChar == 'c')
                     {
                         //send concurrent (test for raceconditions)
                         var sendTasks = msgs
@@ -161,10 +162,7 @@ namespace MQTTnet.TestApp.NetCore
         private static Task PublishSingleMessage(IMqttClient client, MqttApplicationMessage applicationMessage, ref int count)
         {
             Interlocked.Increment(ref count);
-            return Task.Run(() =>
-           {
-               return client.PublishAsync(applicationMessage);
-           });
+            return Task.Run(() => client.PublishAsync(applicationMessage));
         }
 
         private static async Task RunServerAsync()
diff --git a/Tests/MQTTnet.TestApp.NetCore/Program.cs b/Tests/MQTTnet.TestApp.NetCore/Program.cs
index 31d26db..88130cb 100644
--- a/Tests/MQTTnet.TestApp.NetCore/Program.cs
+++ b/Tests/MQTTnet.TestApp.NetCore/Program.cs
@@ -6,16 +6,18 @@ using MQTTnet.Core.Protocol;
 using MQTTnet.Core.Server;
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using Newtonsoft.Json;
 
 namespace MQTTnet.TestApp.NetCore
 {
     public static class Program
     {
-        public static void Main(string[] args)
+        public static void Main()
         {
             Console.WriteLine("MQTTnet - TestApp.NetFramework");
             Console.WriteLine("1 = Start client");
@@ -24,12 +26,12 @@ namespace MQTTnet.TestApp.NetCore
             var pressedKey = Console.ReadKey(true);
             if (pressedKey.Key == ConsoleKey.D1)
             {
-                Task.Run(() => RunClientAsync(args));
+                Task.Run(RunClientAsync);
                 Thread.Sleep(Timeout.Infinite);
             }
             else if (pressedKey.Key == ConsoleKey.D2)
             {
-                Task.Run(() => RunServerAsync(args));
+                Task.Run(() => RunServerAsync());
                 Thread.Sleep(Timeout.Infinite);
             }
             else if (pressedKey.Key == ConsoleKey.D3)
@@ -39,7 +41,7 @@ namespace MQTTnet.TestApp.NetCore
             }
         }
 
-        private static async Task RunClientAsync(string[] arguments)
+        private static async Task RunClientAsync()
         {
             MqttNetTrace.TraceMessagePublished += (s, e) =>
             {
@@ -128,7 +130,7 @@ namespace MQTTnet.TestApp.NetCore
             }
         }
 
-        private static void RunServerAsync(string[] arguments)
+        private static Task RunServerAsync()
         {
             MqttNetTrace.TraceMessagePublished += (s, e) =>
             {
@@ -157,10 +159,21 @@ namespace MQTTnet.TestApp.NetCore
                     }
                 };
 
+                options.Storage = new RetainedMessageHandler();
+
+
                 var certificate = new X509Certificate(@"C:\certs\test\test.cer", "");
                 options.TlsEndpointOptions.Certificate = certificate.Export(X509ContentType.Cert);
+                options.ConnectionBacklog = 5;
+                options.DefaultEndpointOptions.IsEnabled = true;
+                options.TlsEndpointOptions.IsEnabled = false;
 
                 var mqttServer = new MqttServerFactory().CreateMqttServer(options);
+                mqttServer.ClientDisconnected += (s, e) =>
+                {
+                    Console.Write("Client disconnected event fired.");
+                };
+
                 mqttServer.StartAsync();
 
                 Console.WriteLine("Press any key to exit.");
@@ -174,6 +187,34 @@ namespace MQTTnet.TestApp.NetCore
             }
 
             Console.ReadLine();
+            return Task.FromResult(0);
+        }
+    }
+
+    public class RetainedMessageHandler : IMqttServerStorage
+    {
+        private const string Filename = "C:\\MQTT\\RetainedMessages.json";
+
+        public Task SaveRetainedMessagesAsync(IList<MqttApplicationMessage> messages)
+        {
+            File.WriteAllText(Filename, JsonConvert.SerializeObject(messages));
+            return Task.FromResult(0);
+        }
+
+        public Task<IList<MqttApplicationMessage>> LoadRetainedMessagesAsync()
+        {
+            IList<MqttApplicationMessage> retainedMessages;
+            if (File.Exists(Filename))
+            {
+                var json = File.ReadAllText(Filename);
+                retainedMessages = JsonConvert.DeserializeObject<List<MqttApplicationMessage>>(json);
+            }
+            else
+            {
+                retainedMessages = new List<MqttApplicationMessage>();
+            }
+            
+            return Task.FromResult(retainedMessages);
         }
     }
 }
diff --git a/Tests/MQTTnet.TestApp.UniversalWindows/App.xaml.cs b/Tests/MQTTnet.TestApp.UniversalWindows/App.xaml.cs
index de5a9f8..3ed0757 100644
--- a/Tests/MQTTnet.TestApp.UniversalWindows/App.xaml.cs
+++ b/Tests/MQTTnet.TestApp.UniversalWindows/App.xaml.cs
@@ -1,35 +1,18 @@
 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
+    sealed partial class App
     {
-        /// <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;
+            InitializeComponent();
+            Suspending += OnSuspending;
         }
 
         /// <summary>
@@ -39,11 +22,9 @@ namespace MQTTnet.TestApp.UniversalWindows
         /// <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)
+            if (!(Window.Current.Content is Frame rootFrame))
             {
                 // Create a Frame to act as the navigation context and navigate to the first page
                 rootFrame = new Frame();
diff --git a/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml b/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml
index b097b50..e2b0a18 100644
--- a/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml
+++ b/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml
@@ -58,7 +58,7 @@
 
                     <TextBlock>QoS:</TextBlock>
                     <StackPanel Orientation="Horizontal">
-                        <RadioButton Margin="0,0,10,0" x:Name="QoS0" IsChecked="True" GroupName="qos">0 (At most once)</RadioButton>
+                        <RadioButton Margin="0,0,10,0" IsChecked="True" GroupName="qos">0 (At most once)</RadioButton>
                         <RadioButton Margin="0,0,10,0" x:Name="QoS1" GroupName="qos">1 (At least once)</RadioButton>
                         <RadioButton Margin="0,0,10,0" x:Name="QoS2" GroupName="qos">2 (Exactly once)</RadioButton>
                     </StackPanel>
@@ -73,7 +73,7 @@
 
                     <TextBlock>QoS:</TextBlock>
                     <StackPanel Orientation="Horizontal">
-                        <RadioButton Margin="0,0,10,0" x:Name="SubscribeQoS0" IsChecked="True" GroupName="sqos">0 (At most once)</RadioButton>
+                        <RadioButton Margin="0,0,10,0" IsChecked="True" GroupName="sqos">0 (At most once)</RadioButton>
                         <RadioButton Margin="0,0,10,0" x:Name="SubscribeQoS1" GroupName="sqos">1 (At least once)</RadioButton>
                         <RadioButton Margin="0,0,10,0" x:Name="SubscribeQoS2" GroupName="sqos">2 (Exactly once)</RadioButton>
                     </StackPanel>
diff --git a/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml.cs b/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml.cs
index 07d5955..de795d5 100644
--- a/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml.cs
+++ b/Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml.cs
@@ -41,7 +41,7 @@ namespace MQTTnet.TestApp.UniversalWindows
 
         private async void Connect(object sender, RoutedEventArgs e)
         {
-            MqttClientOptions options = null;
+            BaseMqttClientOptions options = null;
             if (UseTcp.IsChecked == true)
             {
                 options = new MqttClientTcpOptions
@@ -195,6 +195,8 @@ namespace MQTTnet.TestApp.UniversalWindows
             }
         }
 
+        // This code is for the Wiki at GitHub!
+        // ReSharper disable once UnusedMember.Local
         private async Task WikiCode()
         {
             var mqttClient = new MqttClientFactory().CreateMqttClient();