Question

I am using the following code (built from answers to my previous questions on SO):

public void Start()
{
    listener = new TcpListener(IPAddress.Any, 9030);
    listener.Start();
    Console.WriteLine("Listening...");
    StartAccept();
}

private void StartAccept()
{        
    listener.BeginAcceptTcpClient(HandleAsyncConnection, listener);            
}

private void HandleAsyncConnection(IAsyncResult res)
{
    StartAccept();
    TcpClient client = listener.EndAcceptTcpClient(res);

    StringBuilder sb = new StringBuilder();
    var data = new byte[client.ReceiveBufferSize];

    using (NetworkStream ns = client.GetStream())
    {
        int readCount;
        while ((readCount = ns.Read(data, 0, client.ReceiveBufferSize)) != 0)
        {
            sb.Append(Encoding.UTF8.GetString(data, 0, readCount));
        }

        // Do work

        // Test reply
        Byte[] replyData = System.Text.Encoding.ASCII.GetBytes(DateTime.Now.ToString());
        ns.Write(replyData, 0, replyData.Length);
        ns.Flush();
        ns.Close();
    }

    client.Close();
}

The line “Do work” represents where I will do the required processing for my client.

However I can’t see how to use this code to read the client’s data and then reply to it. When using this code I can read perfectly what is sent by my client, however once that occurs the client locks up and eventually complains that the connection was terminated. It does not receive my reply.

Any ideas on how to fix this?

Answer 1

Okay, first of all, you are mixing asynchronous calls (BeginAcceptTcpClient) and synchronous (Read and Write) calls. That completely kills the purpose of asynchronous code. Second, maybe this is why your socket gets closed ? Performing a sync op on an async socket. I’m not sure, but without the client code it’s impossible to tell.

Anyway, this is NOT how you build an asynchronous, multi-client server.

Here is a fully asynchronous server implementation : http://msdn.microsoft.com/en-us/library/fx6588te.aspx