#194 fixed a bug in the Dispose-Logic of TelnetAppender

Author: FreeAndNil

src/log4net.Tests/Appender/Internal/SimpleTelnetClient.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Net;
+using System.Net.Sockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace log4net.Tests.Appender.Internal
+{
+  /// <summary>
+  /// Telnet Client for unit testing
+  /// </summary>
+  /// <param name="received">Callback for received messages</param>
+  /// <param name="port">TCP-Port to use</param>
+  internal sealed class SimpleTelnetClient(
+    Action<string> received, int port) : IDisposable
+  {
+    private readonly CancellationTokenSource cancellationTokenSource = new();
+    private readonly TcpClient client = new();
+
+    /// <summary>
+    /// Runs the client (in a task)
+    /// </summary>
+    internal void Run() => Task.Run(() =>
+    {
+      client.Connect(new IPEndPoint(IPAddress.Loopback, port));
+      // Get a stream object for reading and writing
+      using NetworkStream stream = client.GetStream();
+
+      int i;
+      byte[] bytes = new byte[256];
+
+      // Loop to receive all the data sent by the server 
+      while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
+      {
+        string data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
+        received(data);
+        if (cancellationTokenSource.Token.IsCancellationRequested)
+        {
+          return;
+        }
+      }
+    }, cancellationTokenSource.Token);
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+      cancellationTokenSource.Cancel();
+      cancellationTokenSource.Dispose();
+      client.Dispose();
+    }
+  }
+}

src/log4net.Tests/Appender/TelnetAppenderTest.cs

@@ -0,0 +1,92 @@
+#region Apache License
+//
+// Licensed to the Apache Software Foundation (ASF) under one or more 
+// contributor license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership. 
+// The ASF licenses this file to you under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with 
+// the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Xml;
+using log4net.Appender;
+using log4net.Config;
+using log4net.Core;
+using log4net.Repository;
+using log4net.Tests.Appender.Internal;
+using NUnit.Framework;
+
+namespace log4net.Tests.Appender;
+
+/// <summary>
+/// Tests for <see cref="TelnetAppender"/>
+/// </summary>
+[TestFixture]
+public sealed class TelnetAppenderTest
+{
+  /// <summary>
+  /// Simple Test für the <see cref="TelnetAppender"/>
+  /// </summary>
+  /// <remarks>
+  /// https://github.com/apache/logging-log4net/issues/194
+  /// https://stackoverflow.com/questions/79053363/log4net-telnetappender-doesnt-work-after-migrate-to-log4net-3
+  /// </remarks>
+  [Test]
+  public void TelnetTest()
+  {
+    List<string> received = [];
+
+    XmlDocument log4netConfig = new();
+    int port = 9090;
+    log4netConfig.LoadXml($"""
+    <log4net>
+      <appender name="TelnetAppender" type="log4net.Appender.TelnetAppender">
+        <port value="{port}" />
+        <layout type="log4net.Layout.PatternLayout">
+          <conversionPattern value="%date %-5level - %message%newline" />
+        </layout>
+      </appender>
+      <root>
+        <level value="INFO"/>
+        <appender-ref ref="TelnetAppender"/>
+      </root>
+    </log4net>
+""");
+    string logId = Guid.NewGuid().ToString();
+    ILoggerRepository repository = LogManager.CreateRepository(logId);
+    XmlConfigurator.Configure(repository, log4netConfig["log4net"]!);
+    using (SimpleTelnetClient telnetClient = new(Received, port))
+    {
+      telnetClient.Run();
+      WaitForReceived(1); // wait for welcome message
+      ILogger logger = repository.GetLogger("Telnet");
+      logger.Log(typeof(TelnetAppenderTest), Level.Info, logId, null);
+      WaitForReceived(2); // wait for log message
+    }
+    repository.Shutdown();
+    Assert.AreEqual(2, received.Count);
+    StringAssert.Contains(logId, received[1]);
+
+    void Received(string message) => received.Add(message);
+
+    void WaitForReceived(int count)
+    {
+      while (received.Count < count)
+      {
+        Thread.Sleep(10);
+      }
+    }
+  }
+}