After stopping the thread, can I cancel the listen operation with a variable?

Question

I listen to a port in a thread with the following method. While waiting in WaitOne method, I stop the thread (I am doing IsCancellationRequested true) and I can not close the listener object. Then I get an error when I want to listen to the same port.

Can I bind a listener object to a variable? If that variable is false, it will do an automatic shutdown.

I do not want to check that the thread is stopped with a separate thread and close the listener.

public void StartListening(Connection connection)
{
    // There are codes here..
    try
    {
        listener.Bind(localEndPoint);
        listener.Listen(2);

        while (connection.CancellationTokenSource.IsCancellationRequested == false)
        {                
            allDone.Reset();                    
            listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
            allDone.WaitOne(); // While I'm waiting here, I'm making the 'IsCancellationRequested' variable true.
        }

        listener.Close();
    }
    catch (Exception e)
    {
        // There are codes here..
    }

    // There are codes here..
}

Note: The Connection class is a class I created that contains theSystem.Threading.CancellationTokenSource CancellationTokenSource property.

Answer 1

I don't know the precise structure of the connection, but...

You could try waiting on two handles. (untested)

var handles = new EventWaitHandle[] 
{ 
    allDone, 
    connection.CancellationTokenSource.Token.WaitHandle 
};

int index = EventWaitHandle.WaitAny(handles);

WaitAny returns the index of the waithandle whois set. So determine if you want to break your while or not.

---

Maybee something like:

public void StartListening(Connection connection)
{
    // There are codes here..
    try
    {
        listener.Bind(localEndPoint);
        listener.Listen(2);

        var handles = new EventWaitHandle[] 
        { 
            allDone, 
            connection.CancellationTokenSource.Token.WaitHandle 
        };

        do
        {                
            allDone.Reset();                    
            listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
        }
        while(EventWaitHandle.WaitAny(handles) == 0);

        listener.Close();
    }
    catch (Exception e)
    {
        // There are codes here..
    }

    // There are codes here..
}

---

A way to cancel the listener. Can't make up something nicer at the moment. If someone has a better way... feel free ;-)

ManualResetEvent _listenerTerminated = new ManualResetEvent(false);

// <snip>

listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);

private void AcceptCallback(IAsyncResult ar)
{
    // before calling EndAccept, check an event.
    if(_listenerTerminated.WaitOne(0))
        return;

    var clientSocket = listener.EndAccept(asyncResult);
}

// <snip>

do
{                
    allDone.Reset();                    
    listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
}
while(EventWaitHandle.WaitAny(handles) == 0);

_listenerTerminated.Set();

listener.Close();