Winforms server socket application

Question

I'm trying to create a winforms application that listens for traffic on port 10000, and basically works as a middle man for a client application and a remote database. It should have a listen and accept thread which opens a separate client thread when a client connects. This client thread would then handle communication with the client program. The listener application has two listboxes with information on the user that is connecting and the action that is being performed.

For now, I'm trying to use the example program Microsoft gives here and modify it according to my needs, but if anyone has any suggestions on where else I might look I'd love to hear it.

As I try to stumble through this, one thing I haven't been able to figure out yet is how to get this listener going without locking down my computer. Here is my form code (including an exit button and a button that clears my listboxes):

public partial class Form1 : Form {

    public Form1() {
        InitializeComponent();
    }

    private void btnExit_Click(object sender, EventArgs e) {
        this.Close();
    }

    private void btnClearList_Click(object sender, EventArgs e) {
        this.lbActionLog.Items.Clear();
        this.lbUserLog.Items.Clear();
        count = 0;
        this.txtCount.Text = count.ToString();
    }

    private void Form1_Load(object sender, EventArgs e) {
        Server begin = new Server();
        begin.createListener();
    }
}

and here is my listener code that is called with begin.createListener:

int servPort = 10000;
        public void createListener() {
            // Create an instance of the TcpListener class.
            TcpListener tcpListener = null;
            IPAddress ipAddress = Dns.GetHostEntry("localhost").AddressList[0];
            string output = "";

            try {
                // Set the listener on the local IP address and specify the port.
                // 
                tcpListener = new TcpListener(ipAddress, servPort);
                tcpListener.Start();
                output = "Waiting for a connection...";
            }
            catch (Exception e) {
                output = "Error: " + e.ToString();
                MessageBox.Show(output);
            }
            while (true) {
                // Always use a Sleep call in a while(true) loop 
                // to avoid locking up your CPU.
                Thread.Sleep(10);
                // Create socket
                //Socket socket = tcpListener.AcceptSocket(); 
                TcpClient tcpClient = tcpListener.AcceptTcpClient();
                // Read the data stream from the client. 
                byte[] bytes = new byte[256];
                NetworkStream stream = tcpClient.GetStream();
                stream.Read(bytes, 0, bytes.Length);
                SocketHelper helper = new SocketHelper();
                helper.processMsg(tcpClient, stream, bytes);
            }
        }

Right now, this just stops on tcpListener.AcceptSocket. The form never loads, and obviously the listboxes aren't being populated. How can I get this listener going automatically with the start of the application, and still load the form and update the listboxes? I want this application to start and be ready at any time to accept a connection, without needing to have one already sitting there waiting.

Answer 1

You are using a blocking method so that the Form1_Load never ends because it awaits incoming connections.

A simple workaround could be to start a new thread that handles connections:

private void Form1_Load(object sender, EventArgs e) {
    new Thread( 
        () =>
        {
           Server begin = new Server();
           begin.createListener();
        } 
    ).Start();
}