TcpListener.AcceptSocket() fails in a Windows Service

Question

I have an instance of the following code that executes correctly in Debug or as a standalone Windows application:

TcpListener tcpListener = new TcpListener(IPAddress.Any, 4554);
tcpListener.Start();

while (true)
{
    try
    {
        using (Socket socket = tcpListener.AcceptSocket())
        {
            // Code here is reached in Debug or as a Console Application
            // but not as a Windows Service
        }
    }
    catch (SocketException se)
    {
        // This is never reached
    }
    catch (Exception ex)
    {
        // This is never reached
    }
    finally
    {
        // This is never reached in the Windows Service
    }
}

However, when I install it as a Windows Service, it crashes on tcpListener.AcceptSocket(), and logs the following to the Event Viewer:

An unhandled exception ('System.Net.Sockets.SocketException') occurred in MyService.exe [768]. Just-In-Time debugging this exception failed with the following error: The operation attempted is not supported.

Even trying to catch the exception I am unable to log anything more. Stepping through code in Debug accomplishes nothing because the code successfully blocks the application and waits for a client connection.

Is there a way to implement this for a Windows Service?

It's likely that the `Start` that is what is throwing the `SocketException`. Since it isn't in your try, your catch and finally aren't being hit. Move your `Start` into your try, and examine the ErrorCode property of your `SocketException` in your catch statement. That will give you a better idea of what is wrong. Then check the ErrorCode against [this list](http://msdn.microsoft.com/en-us/library/windows/desktop/ms740668(v=vs.85).aspx) to see what the exact problem is. — vcsjones, Jul 22 '14 at 19:27
Make yourself familiar with how to debug services. It's possible. — usr, Jul 22 '14 at 19:39
@vcsjones I tried that with the same result. I also added logging just before and after `tcpListener.AcceptSocket()`, it successfully logs before the call but not after. — Chris Schiffhauer, Jul 22 '14 at 19:48
Thank you @usr. I did as you advised and discovered my service logic was re-instantiating the class. — Chris Schiffhauer, Jul 22 '14 at 20:09

score 1 · Accepted Answer · edited May 23 '17 at 12:21

usr's advice (and this answer) led me to a bug in the code. The ServiceBase class contained the following:

protected override void OnStart(string[] args)
{
    _worker = new Thread(ExecuteService);
    _worker.Start();
}

private void ExecuteService()
{
    for (;;)
    {
         if (_stop.WaitOne(1000))
        {
            new TcpServer().StartTcpServer();
            return;
        }
    }
}

The correct implementation was to remove the for loop, which was re-instantiating the listener. Here is the final code:

protected override void OnStart(string[] args)
{
    _worker = new Thread(ExecuteService);
    _worker.Start();
}

private static void ExecuteService()
{
    new TcpServer().StartTcpServer();
}

TcpListener.AcceptSocket() fails in a Windows Service

1 Answers1