Question

I have created an asynchronous server that can read in messages from any number of clients. My server code is closely related to this example: http://msdn.microsoft.com/en-us/library/fx6588te.aspx

After a client connects I would like to periodically send out data to that client, maybe 2 or 3 times per second. I can’t think of a good way to achieve this with an asynchronous send(). I’m assuming that some sort of timing mechanism would need to be added to my AcceptCallback() method because that is where the connection to the client happens.

In the previous version of my server I used blocking sockets and just looped my send() method in an infinite while() loop and called sleep() to get the timing down.

Here’s what I’m thinking:

public void AcceptCallback(IAsyncResult ar)
    {
        allDone.Set(); // Signal the main thread to continue.

        // Get the socket that handles the client request.
        Socket listener = (Socket)ar.AsyncState;
        Socket handler = listener.EndAccept(ar);
        IPEndPoint remotePoint = (IPEndPoint)handler.RemoteEndPoint;
        IPAddress remoteAddress = remotePoint.Address;
        Console.WriteLine("Connected to {0}!", remoteAddress.ToString());

        // Create the state object.
        StateObject state = new StateObject();
        state.workSocket = handler;

        //Start periodically sending here??

        handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
            new AsyncCallback(ReadCallback), state);
    }

Answer 1

I would set up a Timer object to send data to the client. Instantiate and start the timer in the AcceptCallback method at your comment. You’ll have to keep track of information to allow that timer callback to send data to the client (like the socket, and some sort of test to allow it to stop–although you can simply turn the timer off, but you’d have to keep track of the timer in that case).

BTW, never call Sleep in situations like this because that commits your thread to sitting around for some period of time and you can’t easily abort it to get the thread back (to exit or use for something else).