diff --git a/Build/MQTTnet.nuspec b/Build/MQTTnet.nuspec
index f0e4c3d..3735636 100644
--- a/Build/MQTTnet.nuspec
+++ b/Build/MQTTnet.nuspec
@@ -15,6 +15,7 @@
 * [Core] Added extension method to allow usage of _WebSocket4Net_ in clients to fix issues with AWS and Xamarin.
 * [Core] Fixed usage of wrong data type for passwords (string -> byte[]).
 * [Core] Fixed an _ObjectDisposedException_ when sending data using a WebSocket channel.
+* [Core] Performance optimizations.
 * [Client] Added support for extended authentication exchange.
 * [Client] Exposed MQTTv5 CONNACK values to client.
 * [Client] Added _MqttClientSubscribeOptionsBuilder_.
diff --git a/Source/MQTTnet.AspnetCore/SpanBasedMqttPacketBodyReader.cs b/Source/MQTTnet.AspnetCore/SpanBasedMqttPacketBodyReader.cs
index 2b118f7..58edcf8 100644
--- a/Source/MQTTnet.AspnetCore/SpanBasedMqttPacketBodyReader.cs
+++ b/Source/MQTTnet.AspnetCore/SpanBasedMqttPacketBodyReader.cs
@@ -9,6 +9,7 @@ namespace MQTTnet.AspNetCore
     public class SpanBasedMqttPacketBodyReader : IMqttPacketBodyReader
     {
         private ReadOnlyMemory<byte> _buffer;
+
         private int _offset;
         
         public void SetBuffer(ReadOnlyMemory<byte> buffer)
@@ -17,11 +18,11 @@ namespace MQTTnet.AspNetCore
             _offset = 0;
         }
 
-        public ulong Length => (ulong)_buffer.Length;
+        public int Length => _buffer.Length;
 
         public bool EndOfStream => _buffer.Length.Equals(_offset);
         
-        public ulong Offset => (ulong)_offset;
+        public int Offset => _offset;
 
         public byte ReadByte()
         {
@@ -116,9 +117,9 @@ namespace MQTTnet.AspNetCore
             throw new MqttProtocolViolationException("Boolean values can be 0 or 1 only.");
         }
 
-        public void Seek(ulong position)
+        public void Seek(int position)
         {
-            _offset = (int)position;
+            _offset = position;
         }
     }
 }
diff --git a/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs b/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs
index 59f1c9a..74d148d 100644
--- a/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs
+++ b/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs
@@ -31,7 +31,7 @@ namespace MQTTnet.Extensions.ManagedClient
 
         private ManagedMqttClientStorageManager _storageManager;
 
-        private bool _disposed = false;
+        private bool _disposed;
         private bool _subscriptionsNotPushed;
 
         public ManagedMqttClient(IMqttClient mqttClient, IMqttNetChildLogger logger)
@@ -102,9 +102,8 @@ namespace MQTTnet.Extensions.ManagedClient
 
             _connectionCancellationToken = new CancellationTokenSource();
 
-#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
             _maintainConnectionTask = Task.Run(() => MaintainConnectionAsync(_connectionCancellationToken.Token), _connectionCancellationToken.Token);
-#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            _maintainConnectionTask.Forget(_logger);
 
             _logger.Info("Started");
         }
@@ -333,20 +332,20 @@ namespace MQTTnet.Extensions.ManagedClient
             }
         }
 
-        private void PublishQueuedMessages(CancellationToken cancellationToken)
+        private async Task PublishQueuedMessagesAsync(CancellationToken cancellationToken)
         {
             try
             {
                 while (!cancellationToken.IsCancellationRequested && _mqttClient.IsConnected)
                 {
-                    //Peek at the message without dequeueing in order to prevent the
-                    //possibility of the queue growing beyond the configured cap.
-                    //Previously, messages could be re-enqueued if there was an
-                    //exception, and this re-enqueueing did not honor the cap.
-                    //Furthermore, because re-enqueueing would shuffle the order
-                    //of the messages, the DropOldestQueuedMessage strategy would
-                    //be unable to know which message is actually the oldest and would
-                    //instead drop the first item in the queue.
+                    // Peek at the message without dequeueing in order to prevent the
+                    // possibility of the queue growing beyond the configured cap.
+                    // Previously, messages could be re-enqueued if there was an
+                    // exception, and this re-enqueueing did not honor the cap.
+                    // Furthermore, because re-enqueueing would shuffle the order
+                    // of the messages, the DropOldestQueuedMessage strategy would
+                    // be unable to know which message is actually the oldest and would
+                    // instead drop the first item in the queue.
                     var message = _messageQueue.PeekAndWait();
                     if (message == null)
                     {
@@ -355,7 +354,7 @@ namespace MQTTnet.Extensions.ManagedClient
 
                     cancellationToken.ThrowIfCancellationRequested();
 
-                    TryPublishQueuedMessage(message);
+                    await TryPublishQueuedMessageAsync(message).ConfigureAwait(false);
                 }
             }
             catch (OperationCanceledException)
@@ -371,23 +370,28 @@ namespace MQTTnet.Extensions.ManagedClient
             }
         }
 
-        private void TryPublishQueuedMessage(ManagedMqttApplicationMessage message)
+        private async Task TryPublishQueuedMessageAsync(ManagedMqttApplicationMessage message)
         {
             Exception transmitException = null;
             try
             {
-                _mqttClient.PublishAsync(message.ApplicationMessage).GetAwaiter().GetResult();
+                await _mqttClient.PublishAsync(message.ApplicationMessage).ConfigureAwait(false);
+
                 lock (_messageQueue) //lock to avoid conflict with this.PublishAsync
                 {
-                    //While publishing this message, this.PublishAsync could have booted this
-                    //message off the queue to make room for another (when using a cap
-                    //with the DropOldestQueuedMessage strategy).  If the first item
-                    //in the queue is equal to this message, then it's safe to remove
-                    //it from the queue.  If not, that means this.PublishAsync has already
-                    //removed it, in which case we don't want to do anything.
+                    // While publishing this message, this.PublishAsync could have booted this
+                    // message off the queue to make room for another (when using a cap
+                    // with the DropOldestQueuedMessage strategy).  If the first item
+                    // in the queue is equal to this message, then it's safe to remove
+                    // it from the queue.  If not, that means this.PublishAsync has already
+                    // removed it, in which case we don't want to do anything.
                     _messageQueue.RemoveFirst(i => i.Id.Equals(message.Id));
                 }
-                _storageManager?.RemoveAsync(message).GetAwaiter().GetResult();
+
+                if (_storageManager != null)
+                {
+                    await _storageManager.RemoveAsync(message).ConfigureAwait(false);
+                }
             }
             catch (MqttCommunicationException exception)
             {
@@ -408,6 +412,11 @@ namespace MQTTnet.Extensions.ManagedClient
                     {
                         _messageQueue.RemoveFirst(i => i.Id.Equals(message.Id));
                     }
+
+                    if (_storageManager != null)
+                    {
+                        await _storageManager.RemoveAsync(message).ConfigureAwait(false);
+                    }
                 }
             }
             catch (Exception exception)
@@ -417,7 +426,12 @@ namespace MQTTnet.Extensions.ManagedClient
             }
             finally
             {
-                ApplicationMessageProcessedHandler?.HandleApplicationMessageProcessedAsync(new ApplicationMessageProcessedEventArgs(message, transmitException)).GetAwaiter().GetResult();
+                var eventHandler = ApplicationMessageProcessedHandler;
+                if (eventHandler != null)
+                {
+                    var eventArguments = new ApplicationMessageProcessedEventArgs(message, transmitException);
+                    await eventHandler.HandleApplicationMessageProcessedAsync(eventArguments).ConfigureAwait(false);
+                }
             }
         }
 
@@ -502,7 +516,7 @@ namespace MQTTnet.Extensions.ManagedClient
             var cts = new CancellationTokenSource();
             _publishingCancellationToken = cts;
 
-            Task.Factory.StartNew(() => PublishQueuedMessages(cts.Token), cts.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default);
+            Task.Run(() => PublishQueuedMessagesAsync(cts.Token), cts.Token).Forget(_logger);
         }
 
         private void StopPublishing()
diff --git a/Source/MQTTnet.Server/Mqtt/MqttServerConnectionValidator.cs b/Source/MQTTnet.Server/Mqtt/MqttServerConnectionValidator.cs
index 4e13c83..3b1a2fc 100644
--- a/Source/MQTTnet.Server/Mqtt/MqttServerConnectionValidator.cs
+++ b/Source/MQTTnet.Server/Mqtt/MqttServerConnectionValidator.cs
@@ -29,10 +29,10 @@ namespace MQTTnet.Server.Mqtt
                     { "client_id", context.ClientId },
                     { "username", context.Username },
                     { "password", context.Password },
-                    { "raw_password", new Bytes(context.RawPassword) },
+                    { "raw_password", new Bytes(context.RawPassword ?? new byte[0]) },
                     { "clean_session", context.CleanSession},
                     { "authentication_method", context.AuthenticationMethod},
-                    { "authentication_data", new Bytes(context.AuthenticationData)},
+                    { "authentication_data", new Bytes(context.AuthenticationData ?? new byte[0]) },
 
                     { "result", PythonConvert.Pythonfy(context.ReasonCode) }
                 };
@@ -44,6 +44,8 @@ namespace MQTTnet.Server.Mqtt
             catch (Exception exception)
             {
                 _logger.LogError(exception, "Error while validating client connection.");
+
+                context.ReasonCode = MqttConnectReasonCode.UnspecifiedError;
             }
 
             return Task.CompletedTask;
diff --git a/Source/MQTTnet.Server/Mqtt/MqttServerService.cs b/Source/MQTTnet.Server/Mqtt/MqttServerService.cs
index 6323738..efb0010 100644
--- a/Source/MQTTnet.Server/Mqtt/MqttServerService.cs
+++ b/Source/MQTTnet.Server/Mqtt/MqttServerService.cs
@@ -66,7 +66,10 @@ namespace MQTTnet.Server.Mqtt
 
             var adapters = new List<IMqttServerAdapter>
             {
-                new MqttTcpServerAdapter(mqttFactory.Logger.CreateChildLogger()),
+                new MqttTcpServerAdapter(mqttFactory.Logger.CreateChildLogger())
+                {
+                    TreatSocketOpeningErrorAsWarning = true // Opening other ports than for HTTP is not allows in Azure App Services.
+                },
                 _webSocketServerAdapter
             };
 
diff --git a/Source/MQTTnet.Server/appsettings.json b/Source/MQTTnet.Server/appsettings.json
index 9a9ce0d..8ea10d6 100644
--- a/Source/MQTTnet.Server/appsettings.json
+++ b/Source/MQTTnet.Server/appsettings.json
@@ -2,10 +2,10 @@
     "Kestrel": {
         "EndPoints": {
             "Http": {
-                "Url": "http://localhost:80"
+                "Url": "http://*:80"
             },
             "Https": {
-                "Url": "http://localhost:443"
+                "Url": "http://*:443"
             }
         }
     },
diff --git a/Source/MQTTnet/Formatter/IMqttPacketBodyReader.cs b/Source/MQTTnet/Formatter/IMqttPacketBodyReader.cs
index 632c493..2e0f8f0 100644
--- a/Source/MQTTnet/Formatter/IMqttPacketBodyReader.cs
+++ b/Source/MQTTnet/Formatter/IMqttPacketBodyReader.cs
@@ -4,9 +4,9 @@ namespace MQTTnet.Formatter
 {
     public interface IMqttPacketBodyReader
     {
-        ulong Length { get; }
+        int Length { get; }
 
-        ulong Offset { get; }
+        int Offset { get; }
 
         bool EndOfStream { get; }
 
@@ -26,6 +26,6 @@ namespace MQTTnet.Formatter
 
         bool ReadBoolean();
 
-        void Seek(ulong position);
+        void Seek(int position);
     }
 }
diff --git a/Source/MQTTnet/Formatter/MqttPacketBodyReader.cs b/Source/MQTTnet/Formatter/MqttPacketBodyReader.cs
index c45fb3d..1deb1fe 100644
--- a/Source/MQTTnet/Formatter/MqttPacketBodyReader.cs
+++ b/Source/MQTTnet/Formatter/MqttPacketBodyReader.cs
@@ -9,52 +9,42 @@ namespace MQTTnet.Formatter
     public class MqttPacketBodyReader : IMqttPacketBodyReader
     {
         private readonly byte[] _buffer;
-        private readonly ulong _initialOffset;
-        private readonly ulong _length;
+        private readonly int _initialOffset;
+        private readonly int _length;
 
-        public MqttPacketBodyReader(byte[] buffer, int offset, int length)
-         : this(buffer, (ulong)offset, (ulong)length)
-        {
-        }
+        private int _offset;
 
-        public MqttPacketBodyReader(byte[] buffer, ulong offset, ulong length)
+        public MqttPacketBodyReader(byte[] buffer, int offset, int length)
         {
             _buffer = buffer;
             _initialOffset = offset;
-            Offset = offset;
+            _offset = offset;
             _length = length;
         }
 
-        public ulong Offset { get; private set; }
+        public int Offset => _offset;
 
-        public ulong Length => _length - Offset;
+        public int Length => _length - _offset;
 
-        public bool EndOfStream => Offset == _length;
+        public bool EndOfStream => _offset == _length;
 
-        public void Seek(ulong position)
+        public void Seek(int position)
         {
-            Offset = _initialOffset + position;
-        }
-
-        public ArraySegment<byte> Read(uint length)
-        {
-            ValidateReceiveBuffer(length);
-
-            var buffer = new ArraySegment<byte>(_buffer, (int)Offset, (int)length);
-            Offset += length;
-            return buffer;
+            _offset = _initialOffset + position;
         }
 
         public byte ReadByte()
         {
             ValidateReceiveBuffer(1);
-            return _buffer[Offset++];
-        }
 
+            return _buffer[_offset++];
+        }
+        
         public bool ReadBoolean()
         {
             ValidateReceiveBuffer(1);
-            var buffer = _buffer[Offset++];
+
+            var buffer = _buffer[_offset++];
 
             if (buffer == 0)
             {
@@ -71,15 +61,19 @@ namespace MQTTnet.Formatter
 
         public byte[] ReadRemainingData()
         {
-            return new ArraySegment<byte>(_buffer, (int)Offset, (int)(_length - Offset)).ToArray();
+            var bufferLength = _length - _offset;
+            var buffer = new byte[bufferLength];
+            Array.Copy(_buffer, _offset, buffer, 0, bufferLength);
+
+            return buffer;
         }
 
         public ushort ReadTwoByteInteger()
         {
             ValidateReceiveBuffer(2);
 
-            var msb = _buffer[Offset++];
-            var lsb = _buffer[Offset++];
+            var msb = _buffer[_offset++];
+            var lsb = _buffer[_offset++];
             
             return (ushort)(msb << 8 | lsb);
         }
@@ -88,31 +82,14 @@ namespace MQTTnet.Formatter
         {
             ValidateReceiveBuffer(4);
 
-            var byte0 = _buffer[Offset++];
-            var byte1 = _buffer[Offset++];
-            var byte2 = _buffer[Offset++];
-            var byte3 = _buffer[Offset++];
+            var byte0 = _buffer[_offset++];
+            var byte1 = _buffer[_offset++];
+            var byte2 = _buffer[_offset++];
+            var byte3 = _buffer[_offset++];
 
             return (uint)(byte0 << 24 | byte1 << 16 | byte2 << 8 | byte3);
         }
 
-        public byte[] ReadWithLengthPrefix()
-        {
-            return ReadSegmentWithLengthPrefix().ToArray();
-        }
-
-        private ArraySegment<byte> ReadSegmentWithLengthPrefix()
-        {
-            var length = ReadTwoByteInteger();
-
-            ValidateReceiveBuffer(length);
-
-            var result = new ArraySegment<byte>(_buffer, (int)Offset, length);
-            Offset += length;
-
-            return result;
-        }
-
         public uint ReadVariableLengthInteger()
         {
             var multiplier = 1;
@@ -134,13 +111,30 @@ namespace MQTTnet.Formatter
 
             return value;
         }
+        
+        public byte[] ReadWithLengthPrefix()
+        {
+            return ReadSegmentWithLengthPrefix().ToArray();
+        }
+
+        private ArraySegment<byte> ReadSegmentWithLengthPrefix()
+        {
+            var length = ReadTwoByteInteger();
+
+            ValidateReceiveBuffer(length);
+
+            var result = new ArraySegment<byte>(_buffer, _offset, length);
+            _offset += length;
+
+            return result;
+        }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private void ValidateReceiveBuffer(uint length)
+        private void ValidateReceiveBuffer(int length)
         {
-            if (_length < Offset + length)
+            if (_length < _offset + length)
             {
-                throw new ArgumentOutOfRangeException(nameof(_buffer), $"Expected at least {Offset + length} bytes but there are only {_length} bytes");
+                throw new ArgumentOutOfRangeException(nameof(_buffer), $"Expected at least {_offset + length} bytes but there are only {_length} bytes");
             }
         }
 
diff --git a/Source/MQTTnet/Formatter/V5/MqttV500PropertiesReader.cs b/Source/MQTTnet/Formatter/V5/MqttV500PropertiesReader.cs
index df323ae..443cf17 100644
--- a/Source/MQTTnet/Formatter/V5/MqttV500PropertiesReader.cs
+++ b/Source/MQTTnet/Formatter/V5/MqttV500PropertiesReader.cs
@@ -9,8 +9,8 @@ namespace MQTTnet.Formatter.V5
     public class MqttV500PropertiesReader
     {
         private readonly IMqttPacketBodyReader _body;
-        private readonly uint _length;
-        private readonly ulong _targetOffset;
+        private readonly int _length;
+        private readonly int _targetOffset;
 
         public MqttV500PropertiesReader(IMqttPacketBodyReader body)
         {
@@ -18,7 +18,7 @@ namespace MQTTnet.Formatter.V5
 
             if (!body.EndOfStream)
             {
-                _length = body.ReadVariableLengthInteger();
+                _length = (int)body.ReadVariableLengthInteger();
             }
 
             _targetOffset = body.Offset + _length;
diff --git a/Source/MQTTnet/Implementations/MqttTcpServerAdapter.cs b/Source/MQTTnet/Implementations/MqttTcpServerAdapter.cs
index 900ba96..0e28ad0 100644
--- a/Source/MQTTnet/Implementations/MqttTcpServerAdapter.cs
+++ b/Source/MQTTnet/Implementations/MqttTcpServerAdapter.cs
@@ -28,6 +28,8 @@ namespace MQTTnet.Implementations
 
         public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
 
+        public bool TreatSocketOpeningErrorAsWarning { get; set; }
+
         public Task StartAsync(IMqttServerOptions options)
         {
             if (_cancellationTokenSource != null) throw new InvalidOperationException("Server is already started.");
@@ -36,7 +38,7 @@ namespace MQTTnet.Implementations
 
             if (options.DefaultEndpointOptions.IsEnabled)
             {
-                RegisterListeners(options.DefaultEndpointOptions, null);
+                RegisterListeners(options.DefaultEndpointOptions, null, _cancellationTokenSource.Token);
             }
 
             if (options.TlsEndpointOptions.IsEnabled)
@@ -52,7 +54,7 @@ namespace MQTTnet.Implementations
                     throw new InvalidOperationException("The certificate for TLS encryption must contain the private key.");
                 }
 
-                RegisterListeners(options.TlsEndpointOptions, tlsCertificate);
+                RegisterListeners(options.TlsEndpointOptions, tlsCertificate, _cancellationTokenSource.Token);
             }
 
             return Task.FromResult(0);
@@ -78,7 +80,7 @@ namespace MQTTnet.Implementations
             _listeners.Clear();
         }
 
-        private void RegisterListeners(MqttServerTcpEndpointBaseOptions options, X509Certificate2 tlsCertificate)
+        private void RegisterListeners(MqttServerTcpEndpointBaseOptions options, X509Certificate2 tlsCertificate, CancellationToken cancellationToken)
         {
             if (!options.BoundInterNetworkAddress.Equals(IPAddress.None))
             {
@@ -86,14 +88,15 @@ namespace MQTTnet.Implementations
                     AddressFamily.InterNetwork,
                     options,
                     tlsCertificate,
-                    _cancellationTokenSource.Token,
                     _logger)
                 {
                     ClientHandler = OnClientAcceptedAsync
                 };
 
-                listenerV4.Start();
-                _listeners.Add(listenerV4);
+                if (listenerV4.Start(TreatSocketOpeningErrorAsWarning, cancellationToken))
+                {
+                    _listeners.Add(listenerV4);
+                }
             }
 
             if (!options.BoundInterNetworkV6Address.Equals(IPAddress.None))
@@ -102,14 +105,15 @@ namespace MQTTnet.Implementations
                     AddressFamily.InterNetworkV6,
                     options,
                     tlsCertificate,
-                    _cancellationTokenSource.Token,
                     _logger)
                 {
                     ClientHandler = OnClientAcceptedAsync
                 };
 
-                listenerV6.Start();
-                _listeners.Add(listenerV6);
+                if (listenerV6.Start(TreatSocketOpeningErrorAsWarning, cancellationToken))
+                {
+                    _listeners.Add(listenerV6);
+                }
             }
         }
 
diff --git a/Source/MQTTnet/Implementations/MqttTcpServerListener.cs b/Source/MQTTnet/Implementations/MqttTcpServerListener.cs
index fe03c73..fac7376 100644
--- a/Source/MQTTnet/Implementations/MqttTcpServerListener.cs
+++ b/Source/MQTTnet/Implementations/MqttTcpServerListener.cs
@@ -10,6 +10,7 @@ using System.Threading.Tasks;
 using MQTTnet.Adapter;
 using MQTTnet.Diagnostics;
 using MQTTnet.Formatter;
+using MQTTnet.Internal;
 using MQTTnet.Server;
 
 namespace MQTTnet.Implementations
@@ -17,24 +18,23 @@ namespace MQTTnet.Implementations
     public class MqttTcpServerListener : IDisposable
     {
         private readonly IMqttNetChildLogger _logger;
-        private readonly CancellationToken _cancellationToken;
         private readonly AddressFamily _addressFamily;
         private readonly MqttServerTcpEndpointBaseOptions _options;
         private readonly MqttServerTlsTcpEndpointOptions _tlsOptions;
         private readonly X509Certificate2 _tlsCertificate;
+
         private Socket _socket;
+        private IPEndPoint _localEndPoint;
 
         public MqttTcpServerListener(
             AddressFamily addressFamily,
             MqttServerTcpEndpointBaseOptions options,
             X509Certificate2 tlsCertificate,
-            CancellationToken cancellationToken,
             IMqttNetChildLogger logger)
         {
             _addressFamily = addressFamily;
             _options = options;
             _tlsCertificate = tlsCertificate;
-            _cancellationToken = cancellationToken;
             _logger = logger.CreateChildLogger(nameof(MqttTcpServerListener));
 
             if (_options is MqttServerTlsTcpEndpointOptions tlsOptions)
@@ -45,21 +45,38 @@ namespace MQTTnet.Implementations
 
         public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
 
-        public void Start()
+        public bool Start(bool treatErrorsAsWarning, CancellationToken cancellationToken)
         {
-            var boundIp = _options.BoundInterNetworkAddress;
-            if (_addressFamily == AddressFamily.InterNetworkV6)
+            try
             {
-                boundIp = _options.BoundInterNetworkV6Address;
-            }
+                var boundIp = _options.BoundInterNetworkAddress;
+                if (_addressFamily == AddressFamily.InterNetworkV6)
+                {
+                    boundIp = _options.BoundInterNetworkV6Address;
+                }
+
+                _localEndPoint = new IPEndPoint(boundIp, _options.Port);
 
-            _socket = new Socket(_addressFamily, SocketType.Stream, ProtocolType.Tcp);
-            _socket.Bind(new IPEndPoint(boundIp, _options.Port));
+                _logger.Info($"Starting TCP listener for {_localEndPoint} TLS={_tlsCertificate != null}.");
 
-            _logger.Info($"Starting TCP listener for {_socket.LocalEndPoint} TLS={_tlsCertificate != null}.");
+                _socket = new Socket(_addressFamily, SocketType.Stream, ProtocolType.Tcp);
+                _socket.Bind(_localEndPoint);
+                _socket.Listen(_options.ConnectionBacklog);
 
-            _socket.Listen(_options.ConnectionBacklog);
-            Task.Run(() => AcceptClientConnectionsAsync(_cancellationToken), _cancellationToken);
+                Task.Run(() => AcceptClientConnectionsAsync(cancellationToken), cancellationToken).Forget(_logger);
+
+                return true;
+            }
+            catch (Exception exception)
+            {
+                if (!treatErrorsAsWarning)
+                {
+                    throw;
+                }
+
+                _logger.Warning(exception,"Error while creating listener socket for local end point '{0}'.", _localEndPoint);
+                return false;
+            }
         }
 
         public void Dispose()
@@ -82,13 +99,29 @@ namespace MQTTnet.Implementations
 #else
                     var clientSocket = await _socket.AcceptAsync().ConfigureAwait(false);
 #endif
-#pragma warning disable 4014
-                    Task.Run(() => TryHandleClientConnectionAsync(clientSocket), cancellationToken);
-#pragma warning restore 4014
+
+                    if (clientSocket == null)
+                    {
+                        continue;
+                    }
+
+                    Task.Run(() => TryHandleClientConnectionAsync(clientSocket), cancellationToken).Forget(_logger);
+                }
+                catch (OperationCanceledException)
+                {  
                 }
                 catch (Exception exception)
                 {
-                    _logger.Error(exception, $"Error while accepting connection at TCP listener {_socket.LocalEndPoint} TLS={_tlsCertificate != null}.");
+                    if (exception is SocketException socketException)
+                    {
+                        if (socketException.SocketErrorCode == SocketError.ConnectionAborted ||
+                            socketException.SocketErrorCode == SocketError.OperationAborted)
+                        {
+                            continue;
+                        }
+                    }
+                   
+                    _logger.Error(exception, $"Error while accepting connection at TCP listener {_localEndPoint} TLS={_tlsCertificate != null}.");
                     await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
@@ -105,7 +138,7 @@ namespace MQTTnet.Implementations
 
                 _logger.Verbose("Client '{0}' accepted by TCP listener '{1}, {2}'.",
                     remoteEndPoint,
-                    _socket.LocalEndPoint,
+                    _localEndPoint,
                     _addressFamily == AddressFamily.InterNetwork ? "ipv4" : "ipv6");
 
                 clientSocket.NoDelay = _options.NoDelay;
@@ -163,7 +196,7 @@ namespace MQTTnet.Implementations
 
                     _logger.Verbose("Client '{0}' disconnected at TCP listener '{1}, {2}'.",
                         remoteEndPoint,
-                        _socket.LocalEndPoint,
+                        _localEndPoint,
                         _addressFamily == AddressFamily.InterNetwork ? "ipv4" : "ipv6");
                 }
                 catch (Exception disposeException)
diff --git a/Source/MQTTnet/Server/MqttClientConnection.cs b/Source/MQTTnet/Server/MqttClientConnection.cs
index 5ede2c6..ed378bb 100644
--- a/Source/MQTTnet/Server/MqttClientConnection.cs
+++ b/Source/MQTTnet/Server/MqttClientConnection.cs
@@ -7,6 +7,7 @@ using MQTTnet.Client;
 using MQTTnet.Diagnostics;
 using MQTTnet.Exceptions;
 using MQTTnet.Formatter;
+using MQTTnet.Internal;
 using MQTTnet.PacketDispatcher;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
@@ -134,9 +135,7 @@ namespace MQTTnet.Server
 
                 Session.WillMessage = _connectPacket.WillMessage;
 
-#pragma warning disable 4014
-                Task.Run(() => SendPendingPacketsAsync(_cancellationToken.Token), _cancellationToken.Token);
-#pragma warning restore 4014
+                Task.Run(() => SendPendingPacketsAsync(_cancellationToken.Token), _cancellationToken.Token).Forget(_logger);
 
                 // TODO: Change to single thread in SessionManager. Or use SessionManager and stats from KeepAliveMonitor.
                 _keepAliveMonitor.Start(_connectPacket.KeepAlivePeriod, _cancellationToken.Token);
diff --git a/Source/MQTTnet/Server/MqttClientKeepAliveMonitor.cs b/Source/MQTTnet/Server/MqttClientKeepAliveMonitor.cs
index 32effed..deefe4c 100644
--- a/Source/MQTTnet/Server/MqttClientKeepAliveMonitor.cs
+++ b/Source/MQTTnet/Server/MqttClientKeepAliveMonitor.cs
@@ -3,6 +3,7 @@ using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Diagnostics;
+using MQTTnet.Internal;
 
 namespace MQTTnet.Server
 {
@@ -32,7 +33,7 @@ namespace MQTTnet.Server
                 return;
             }
             
-            Task.Run(() => RunAsync(keepAlivePeriod, cancellationToken), cancellationToken).ConfigureAwait(false);
+            Task.Run(() => RunAsync(keepAlivePeriod, cancellationToken), cancellationToken).Forget(_logger);
         }
 
         public void Pause()
diff --git a/Source/MQTTnet/Server/MqttClientSessionsManager.cs b/Source/MQTTnet/Server/MqttClientSessionsManager.cs
index b18f414..c2d5637 100644
--- a/Source/MQTTnet/Server/MqttClientSessionsManager.cs
+++ b/Source/MQTTnet/Server/MqttClientSessionsManager.cs
@@ -47,7 +47,7 @@ namespace MQTTnet.Server
 
         public void Start()
         {
-            Task.Run(() => TryProcessQueuedApplicationMessagesAsync(_cancellationToken), _cancellationToken);
+            Task.Run(() => TryProcessQueuedApplicationMessagesAsync(_cancellationToken), _cancellationToken).Forget(_logger);
         }
 
         public async Task StopAsync()
diff --git a/Tests/MQTTnet.Benchmarks/SerializerBenchmark.cs b/Tests/MQTTnet.Benchmarks/SerializerBenchmark.cs
index 7fbb552..51e7ecb 100644
--- a/Tests/MQTTnet.Benchmarks/SerializerBenchmark.cs
+++ b/Tests/MQTTnet.Benchmarks/SerializerBenchmark.cs
@@ -57,7 +57,7 @@ namespace MQTTnet.Benchmarks
 
                 var receivedPacket = new ReceivedMqttPacket(
                     header.Flags,
-                    new MqttPacketBodyReader(_serializedPacket.Array, (ulong)(_serializedPacket.Count - header.RemainingLength), (ulong)_serializedPacket.Array.Length), 0);
+                    new MqttPacketBodyReader(_serializedPacket.Array, _serializedPacket.Count - header.RemainingLength, _serializedPacket.Array.Length), 0);
 
                 _serializer.Decode(receivedPacket);
             }
diff --git a/Tests/MQTTnet.Core.Tests/Protocol_Tests.cs b/Tests/MQTTnet.Core.Tests/Protocol_Tests.cs
new file mode 100644
index 0000000..41cd1fa
--- /dev/null
+++ b/Tests/MQTTnet.Core.Tests/Protocol_Tests.cs
@@ -0,0 +1,23 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Formatter;
+
+namespace MQTTnet.Tests
+{
+    [TestClass]
+    public class Protocol_Tests
+    {
+        [TestMethod]
+        public void Encode_Four_Byte_Integer()
+        {
+            for (uint i = 0; i < 268435455; i++)
+            {
+                var buffer = MqttPacketWriter.EncodeVariableLengthInteger(i);
+                var reader = new MqttPacketBodyReader(buffer.Array, buffer.Offset, buffer.Count);
+
+                var checkValue = reader.ReadVariableLengthInteger();
+
+                Assert.AreEqual(i, checkValue);
+            }
+        }
+    }
+}
diff --git a/Tests/MQTTnet.Core.Tests/Server_Tests.cs b/Tests/MQTTnet.Core.Tests/Server_Tests.cs
index 31f0847..d10ebaf 100644
--- a/Tests/MQTTnet.Core.Tests/Server_Tests.cs
+++ b/Tests/MQTTnet.Core.Tests/Server_Tests.cs
@@ -22,6 +22,27 @@ namespace MQTTnet.Tests
     [TestClass]
     public class Server_Tests
     {
+        [TestMethod]
+        public async Task Use_Empty_Client_ID()
+        {
+            using (var testEnvironment = new TestEnvironment())
+            {
+                await testEnvironment.StartServerAsync();
+
+                var client = testEnvironment.CreateClient();
+
+                var clientOptions = new MqttClientOptionsBuilder()
+                    .WithTcpServer("localhost", testEnvironment.ServerPort)
+                    .WithClientId(string.Empty)
+                    .Build();
+
+                var connectResult = await client.ConnectAsync(clientOptions);
+
+                Assert.IsFalse(connectResult.IsSessionPresent);
+                Assert.IsTrue(client.IsConnected);
+            }
+        }
+
         [TestMethod]
         public async Task Publish_At_Most_Once_0x00()
         {