Thread.Abort doesn't seem to throw a ThreadAbortException because of AcceptSocket

Question

I am calling ChannelServer.ListeningThread.Abort on the following thread, however nothing seems to happen. I would like to be more specific, but I can't think of anything more. There seems to be no ThreadAbortException that is thrown, and this exception should be thrown regardless of the blocking listener (it works perfectly on threads that are blockingly-receiving).

Important EDIT: With a ManualResetEvent.WaitOne instead of AcceptSocket, as Lyrik has suggested for testing, it works perfectly. How come AcceptSocket blocks the ThreadAbortException?

LINK: This forum thread seems to discuss the same issue, although I cannot figure anything out of it: http://www.tek-tips.com/viewthread.cfm?qid=319436&page=413

ChannelServer.ListeningThread = new Thread(new ThreadStart(delegate()
{
    Log.Inform("Waiting for clients on thread {0}.", Thread.CurrentThread.ManagedThreadId);

    while (true)
    {
        try
        {
            new Thread(new ParameterizedThreadStart(ChannelClientHandler.Initialize)).Start(ChannelServer.Listener.AcceptSocket());
        }
        catch (ThreadAbortException)
        {
            Log.Inform("Aborted client listening thread {0}.", Thread.CurrentThread.ManagedThreadId);
            break;
        }
    }
}));
ChannelServer.ListeningThread.Start();

Answer 1

I'm not sure why you're getting that error, but here is a simple example that works:

ManualResetEvent mrse = new ManualResetEvent(false);
Thread test = new Thread(() =>
    {
        while (true)
        {
            try
            {
                mrse.WaitOne();
            }
            catch (ThreadAbortException)
            {
                Console.WriteLine("No problem here...");
            }
        }
    });

test.IsBackground = true;
test.Start();

Thread.Sleep(1000);
test.Abort();
Console.ReadKey();

So it works for me... I assumed you've stepped through the debugger and your break point inside the catch statement wasn't hit, is that correct?

Note: it's bad practice to call Abort, instead you should call Interrupt and handle the ThreadInterruptedException... it's much safer.

Answer 2

This works, but it's incredibly sloppy and thread-wasting. Could anyone just point me to a way to throw an exception that "AcceptSocket" won't automatically catch?

ChannelServer.ListeningThread = new Thread(new ThreadStart(delegate()
{
    Log.Inform("Waiting for clients on thread {0}.", Thread.CurrentThread.ManagedThreadId);

    while (true)
    {
        try
        {
            ChannelServer.ClientConnected.Reset();
            ChannelServer.Listener.BeginAcceptSocket(new AsyncCallback(ChannelClientHandler.EndAcceptSocket), ChannelServer.Listener);
            ChannelServer.ClientConnected.WaitOne();
        }
        catch (ThreadInterruptedException)
        {
            Log.Inform("Interrupted client listening thread {0}.", Thread.CurrentThread.ManagedThreadId);
            break;
        }
    }
}));
ChannelServer.ListeningThread.Start();

Answer 3

Here a simple AcceptSocket2 extension method (sorry for the lack of imagination regarding the name...). It works exactly as the original AcceptSocket method.

using System;
using System.Net.Sockets;
using System.Threading;

/// <summary>
/// Extensions to TcpListener
/// </summary>
public static class TcpListenerExtensions
{
    /// <summary>
    /// Accepts a pending connection request.
    /// </summary>
    /// <param name="tcpListener">The TCP listener.</param>
    /// <returns>
    /// A <see cref="T:System.Net.Sockets.Socket" /> used to send and receive data.
    /// </returns>
    /// <exception cref="T:System.InvalidOperationException">The listener has not been started with a call to <see cref="M:System.Net.Sockets.TcpListener.Start" />.</exception>
    /// <PermissionSet><IPermission class="System.Security.Permissions.EnvironmentPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Unrestricted="true" /><IPermission class="System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Unrestricted="true" /><IPermission class="System.Security.Permissions.SecurityPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Flags="UnmanagedCode, ControlEvidence" /><IPermission class="System.Diagnostics.PerformanceCounterPermission, System, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Unrestricted="true" /></PermissionSet>
    public static Socket AcceptSocket2(this TcpListener tcpListener)
    {
        Socket socket = null;
        var clientConnected = new ManualResetEvent(false);
        clientConnected.Reset();
        tcpListener.BeginAcceptSocket(delegate(IAsyncResult asyncResult)
        {
            try
            {
                socket = tcpListener.EndAcceptSocket(asyncResult);
            }
            catch (ObjectDisposedException)
            { }
            clientConnected.Set();
        }, null);
        clientConnected.WaitOne();
        return socket;
    }
}