Support for setting port 0 on passive tcp/ip channels

Author: RolandKoenig

MessageCommunicator.Tests/MessageChannelTests.cs

@@ -4,6 +4,7 @@
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using MessageCommunicator.Tests.Util;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
 namespace MessageCommunicator.Tests
@@ -14,20 +15,22 @@ public class MessageChannelTests
         [TestMethod]
         public async Task Check_SimpleTcpIPConnection()
         {
+            var testingPort = TestUtility.GetFreeTcpPort();
+
             var receiveTaskOnPassiveChannel = new TaskCompletionSource<string>();
             var receiveTaskOnActiveChannel = new TaskCompletionSource<string>();
 
             // Define channels
             var passiveChannel = new MessageChannel(
-                new TcpPassiveByteStreamHandlerSettings(IPAddress.Loopback, 40000),
+                new TcpPassiveByteStreamHandlerSettings(IPAddress.Loopback, testingPort),
                 new DefaultMessageRecognizerSettings(Encoding.UTF8),
                 (msg) =>
                 {
                     receiveTaskOnPassiveChannel.SetResult(msg.ToString());
                     msg.ReturnToPool();
                 });
             var activeChannel = new MessageChannel(
-                new TcpActiveByteStreamHandlerSettings("127.0.0.1", 40000),
+                new TcpActiveByteStreamHandlerSettings("127.0.0.1", testingPort),
                 new DefaultMessageRecognizerSettings(Encoding.UTF8),
                 (msg) =>
                 {

MessageCommunicator.Tests/MessageCommunicator.Tests.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.1</TargetFramework>

MessageCommunicator.Tests/Util/TestUtility.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Sockets;
+using System.Runtime.InteropServices.ComTypes;
+using System.Text;
+
+namespace MessageCommunicator.Tests.Util
+{
+    internal static class TestUtility
+    {
+        public static ushort GetFreeTcpPort()
+        {
+            // Simple method do find a free port
+            //  see https://stackoverflow.com/questions/138043/find-the-next-tcp-port-in-net
+
+            var dummyListener = new TcpListener(IPAddress.Loopback, 0);
+
+            dummyListener.Start();
+            var port = (ushort)((IPEndPoint)dummyListener.LocalEndpoint).Port;
+            dummyListener.Stop();
+
+            return port;
+        }
+    }
+}

MessageCommunicator/MessageChannel.cs

@@ -20,12 +20,16 @@ public class MessageChannel
 
         public string RemoteEndpointDescription => _byteStreamHandler.RemoteEndpointDescription;
 
-        public IMessageReceiveHandler ReceiveHandler { get; }
+        public IMessageReceiveHandler? ReceiveHandler
+        {
+            get => _messageRecognizer.ReceiveHandler;
+            set => _messageRecognizer.ReceiveHandler = value;
+        }
 
         public MessageChannel(
             ByteStreamHandlerSettings byteStreamHandlerSettings, 
             MessageRecognizerSettings messageRecognizerSettings, 
-            IMessageReceiveHandler receiveHandler,
+            IMessageReceiveHandler? receiveHandler = null,
             IMessageCommunicatorLogger? logger = null)
         {
             _byteStreamHandler = byteStreamHandlerSettings.CreateByteStreamHandler();

MessageCommunicator/_ByteStreamHandler/_Tcp/TcpPassiveByteStreamHandler.cs

@@ -122,6 +122,7 @@ private async void RunConnectionMainLoop(int loopId)
             CancellationTokenSource? lastCancelTokenSource = null;
             TcpListener? tcpListener = null;
             var reconnectErrorCount = 0;
+            var currentListenerPort = this.ListeningPort;
             while(loopId == _runningLoopCounter)
             {
                 if (tcpListener == null)
@@ -136,6 +137,7 @@ private async void RunConnectionMainLoop(int loopId)
                         }
                         tcpListener = new TcpListener(this.ListeningIPAddress, this.ListeningPort);
                         tcpListener.Start();
+                        currentListenerPort = (ushort)((IPEndPoint)tcpListener.LocalEndpoint).Port;
 
                         reconnectErrorCount = 0;
                         _currentListener = tcpListener;
@@ -144,7 +146,7 @@ private async void RunConnectionMainLoop(int loopId)
                         {
                             this.Log(
                                 LoggingMessageType.Info, 
-                                StringBuffer.Format("TcpListener created for port {0}", this.ListeningPort));
+                                StringBuffer.Format("TcpListener created for port {0}", currentListenerPort));
                         }
                     }
                     catch (Exception ex)
@@ -153,7 +155,7 @@ private async void RunConnectionMainLoop(int loopId)
                         {
                             this.Log(
                                 LoggingMessageType.Error, 
-                                StringBuffer.Format("Error while creating TcpListener for port {0}: {1}", this.ListeningPort, ex.Message),
+                                StringBuffer.Format("Error while creating TcpListener for port {0}: {1}", currentListenerPort, ex.Message),
                                 exception: ex);
                         }
 
@@ -180,7 +182,7 @@ await this.WaitByReconnectWaitTimeAsync(reconnectErrorCount)
                         this.Log(
                             LoggingMessageType.Info,
                             StringBuffer.Format("Listening for incoming connections on port {0}...",
-                                this.ListeningPort));
+                                currentListenerPort));
                     }
 
                     actTcpClient = await tcpListener.AcceptTcpClientAsync()
@@ -194,7 +196,7 @@ await this.WaitByReconnectWaitTimeAsync(reconnectErrorCount)
                             LoggingMessageType.Info,
                             StringBuffer.Format(
                                 "Got new connection on listening port {0}. Connection established between {1} and {2}", 
-                                this.ListeningPort, actLocalEndPoint.ToString(), actPartnerEndPoint.ToString()));
+                                currentListenerPort, actLocalEndPoint.ToString(), actPartnerEndPoint.ToString()));
                     }
                 }
                 catch (ObjectDisposedException)
@@ -210,7 +212,7 @@ await this.WaitByReconnectWaitTimeAsync(reconnectErrorCount)
                     {
                         this.Log(
                             LoggingMessageType.Error, 
-                            StringBuffer.Format("Error while listening for incoming connections on port {0}: {1}", this.ListeningPort, ex.Message),
+                            StringBuffer.Format("Error while listening for incoming connections on port {0}: {1}", currentListenerPort, ex.Message),
                             exception: ex);
                     }