Question

I need to write some code that uses TcpListener. The object that using the TcpListener has 3 possibilities: Listen, Stop Listen, Send message. This is how my code looks:

public class someClass
{
    public bool listenerEnable {get; set; }

    public void StartListen()
    {
        .
        .
        .

        while (listenerEnable)
        {
            // Block until client connected
            TcpClient client = server.AcceptTcpClient();       

            // code that doing something with the client message ... 
        }
    }
}

Now, I’m not sure I know how I can keep the thread safe when I want to stop the listener state (change the listenerEnable to be false).

Also I’m not sure I know how to keep this thread safe when I want to send some message to the client (in some separated method) without stopping the server listener state.

Thanks for any help.

Answer 1

I would suggest waiting on an event rather than waiting on a variable. In your current scheme, consider the case when your loop test for whether listener variable is true. If it is it enters the loop and waits for a incoming connection, and blocks. So now even if another thread sets the listener variable to be false, your loop will not exit till someone connects to it and it processes that connection.

One way of working around the problem above will be to have code like:

WaitHandle[] waitHandles = new WaitHandle[] {endlLoopEvent};
while(true)
{
   int ret = WaitHandle.WaitAny(waitHandles, 100);
   if(WaitTimeout == ret) continue;
   else if(0 == ret) break; //our event has been signaled.
   else
    {
         if(!server.Pending()) continue; //Go back to the loop if no connection pending
         TcpClient client = server.AcceptTcpClient();  
         // You can spawn a thread to service the request.
    }
}

Sending would not affect the loop above, provided it is not in response to a request for connection above.