Fix support for unix sockets (#1995)

* Add support for changing the protocol type on socket level

* Do not set NoDelay when not supported by protocol

* Update release notes

* Fix release notes

.github/workflows/ReleaseNotes.md

@@ -1,6 +1,8 @@
 * [Core] Optimized packet serialization of PUBACK and PUBREC packets for protocol version 5.0.0 (#1939, thanks to @Y-Sindo).
 * [Core] The package inspector is now fully async (#1941).
 * [Core] Fixed decoding of DISCONNECT packet with empty body (#1994, thanks to @Y-Sindo).
+* [Client] Exposed the _EndPoint_ type to support other endpoint types (like Unix Domain Sockets) in client options (#1919).
+* [Client] Fixed support for unix sockets by exposing more options (#1995).
 * [Client] Added a dedicated exception when the client is not connected (#1954, thanks to @marcpiulachs).
 * [Client] The client will now throw a _MqttClientUnexpectedDisconnectReceivedException_ when publishing a QoS 0 message which leads to a server disconnect (BREAKING CHANGE!, #1974, thanks to @fazho).
 * [Client] Exposed the certificate selection event handler in client options (#1984).

Source/MQTTnet.Tests/MqttTcpChannel_Tests.cs

@@ -19,7 +19,7 @@ namespace MQTTnet.Tests
         public async Task Dispose_Channel_While_Used()
         {
             var ct = new CancellationTokenSource();
-            var serverSocket = new CrossPlatformSocket(AddressFamily.InterNetwork);
+            var serverSocket = new CrossPlatformSocket(AddressFamily.InterNetwork, ProtocolType.Tcp);
 
             try
             {
@@ -38,7 +38,7 @@ namespace MQTTnet.Tests
                     }
                 }, ct.Token);
 
-                var clientSocket = new CrossPlatformSocket(AddressFamily.InterNetwork);
+                var clientSocket = new CrossPlatformSocket(AddressFamily.InterNetwork, ProtocolType.Tcp);
                 await clientSocket.ConnectAsync("localhost", 50001, CancellationToken.None);
 
                 var tcpChannel = new MqttTcpChannel(clientSocket.GetStream(), "test", null);

Source/MQTTnet.Tests/Server/Connection_Tests.cs

@@ -23,7 +23,7 @@ namespace MQTTnet.Tests.Server
             {
                 await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithDefaultCommunicationTimeout(TimeSpan.FromSeconds(1)));
 
-                var client = new CrossPlatformSocket(AddressFamily.InterNetwork);
+                var client = new CrossPlatformSocket(AddressFamily.InterNetwork, ProtocolType.Tcp);
                 await client.ConnectAsync("localhost", testEnvironment.ServerPort, CancellationToken.None);
 
                 // Don't send anything. The server should close the connection.
@@ -54,7 +54,7 @@ namespace MQTTnet.Tests.Server
 
                 // Send an invalid packet and ensure that the server will close the connection and stay in a waiting state
                 // forever. This is security related.
-                var client = new CrossPlatformSocket(AddressFamily.InterNetwork);
+                var client = new CrossPlatformSocket(AddressFamily.InterNetwork, ProtocolType.Tcp);
                 await client.ConnectAsync("localhost", testEnvironment.ServerPort, CancellationToken.None);
 
                 var buffer = Encoding.UTF8.GetBytes("Garbage");

Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs

@@ -8,6 +8,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
+using System.Net.Sockets;
 using System.Text;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
@@ -18,13 +19,13 @@ namespace MQTTnet.Client
     public sealed class MqttClientOptionsBuilder
     {
         readonly MqttClientOptions _options = new MqttClientOptions();
+        int? _port;
 
         [Obsolete] MqttClientWebSocketProxyOptions _proxyOptions;
+        EndPoint _remoteEndPoint;
 
         MqttClientTcpOptions _tcpOptions;
         MqttClientTlsOptions _tlsOptions;
-        EndPoint _remoteEndPoint;
-        int? _port;
 
         [Obsolete] MqttClientOptionsBuilderTlsParameters _tlsParameters;
 
@@ -114,6 +115,12 @@ namespace MQTTnet.Client
             return _options;
         }
 
+        public MqttClientOptionsBuilder WithAddressFamily(AddressFamily addressFamily)
+        {
+            _tcpOptions.AddressFamily = addressFamily;
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithAuthentication(string method, byte[] data)
         {
             _options.AuthenticationMethod = method;
@@ -218,6 +225,14 @@ namespace MQTTnet.Client
             return this;
         }
 
+        public MqttClientOptionsBuilder WithEndPoint(EndPoint endPoint)
+        {
+            _remoteEndPoint = endPoint ?? throw new ArgumentNullException(nameof(endPoint));
+            _tcpOptions = new MqttClientTcpOptions();
+
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithExtendedAuthenticationExchangeHandler(IMqttExtendedAuthenticationExchangeHandler handler)
         {
             _options.ExtendedAuthenticationExchangeHandler = handler;
@@ -263,6 +278,12 @@ namespace MQTTnet.Client
             return this;
         }
 
+        public MqttClientOptionsBuilder WithProtocolType(ProtocolType protocolType)
+        {
+            _tcpOptions.ProtocolType = protocolType;
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithProtocolVersion(MqttProtocolVersion value)
         {
             if (value == MqttProtocolVersion.Unknown)
@@ -345,14 +366,6 @@ namespace MQTTnet.Client
             return this;
         }
 
-        public MqttClientOptionsBuilder WithEndPoint(EndPoint endPoint)
-        {
-            _remoteEndPoint = endPoint ?? throw new ArgumentNullException(nameof(endPoint));
-            _tcpOptions = new MqttClientTcpOptions();
-
-            return this;
-        }
-
         public MqttClientOptionsBuilder WithTcpServer(Action<MqttClientTcpOptions> optionsBuilder)
         {
             if (optionsBuilder == null)

Source/MQTTnet/Client/Options/MqttClientTcpOptions.cs

@@ -28,8 +28,20 @@ namespace MQTTnet.Client
         /// </summary>
         public EndPoint LocalEndpoint { get; set; }
 
+        /// <summary>
+        ///     Enables or disables the Nagle algorithm for the socket.
+        ///     This is only supported for TCP.
+        ///     For other protocol types the value is ignored.
+        ///     Default: true
+        /// </summary>
         public bool NoDelay { get; set; } = true;
 
+        /// <summary>
+        ///     The MQTT transport is usually TCP but when using other endpoint types like
+        ///     unix sockets it must be changed (IP for unix sockets).
+        /// </summary>
+        public ProtocolType ProtocolType { get; set; } = ProtocolType.Tcp;
+
         public EndPoint RemoteEndpoint { get; set; }
 
         public MqttClientTlsOptions TlsOptions { get; set; } = new MqttClientTlsOptions();

Source/MQTTnet/Implementations/CrossPlatformSocket.cs

@@ -22,9 +22,9 @@ namespace MQTTnet.Implementations
 
         NetworkStream _networkStream;
 
-        public CrossPlatformSocket(AddressFamily addressFamily)
+        public CrossPlatformSocket(AddressFamily addressFamily, ProtocolType protocolType)
         {
-            _socket = new Socket(addressFamily, SocketType.Stream, ProtocolType.Tcp);
+            _socket = new Socket(addressFamily, SocketType.Stream, protocolType);
 
 #if !NET5_0_OR_GREATER
             _socketDisposeAction = _socket.Dispose;

Source/MQTTnet/Implementations/MqttTcpChannel.cs

@@ -67,7 +67,7 @@ namespace MQTTnet.Implementations
                 }
                 else
                 {
-                    socket = new CrossPlatformSocket(_tcpOptions.AddressFamily);
+                    socket = new CrossPlatformSocket(_tcpOptions.AddressFamily, _tcpOptions.ProtocolType);
                 }
 
                 if (_tcpOptions.LocalEndpoint != null)
@@ -78,7 +78,12 @@ namespace MQTTnet.Implementations
                 socket.ReceiveBufferSize = _tcpOptions.BufferSize;
                 socket.SendBufferSize = _tcpOptions.BufferSize;
                 socket.SendTimeout = (int)_clientOptions.Timeout.TotalMilliseconds;
-                socket.NoDelay = _tcpOptions.NoDelay;
+
+                if (_tcpOptions.ProtocolType == ProtocolType.Tcp)
+                {
+                    // Other protocol types do not support the Nagle algorithm.
+                    socket.NoDelay = _tcpOptions.NoDelay;
+                }
 
                 if (socket.LingerState != null)
                 {

Source/MQTTnet/Implementations/MqttTcpServerListener.cs

@@ -65,7 +65,7 @@ namespace MQTTnet.Implementations
 
                 _logger.Info("Starting TCP listener (Endpoint={0}, TLS={1})", _localEndPoint, _tlsOptions?.CertificateProvider != null);
 
-                _socket = new CrossPlatformSocket(_addressFamily);
+                _socket = new CrossPlatformSocket(_addressFamily, ProtocolType.Tcp);
 
                 // Usage of socket options is described here: https://docs.microsoft.com/en-us/dotnet/api/system.net.sockets.socket.setsocketoption?view=netcore-2.2
                 if (_options.ReuseAddress)