Thread: C# Socket Listen On Specific Port

Hi, I use the TcpListener class built into .net.

Before I show any examples of how to use TcpListener, can I first point out a big mistake you've made based on the code you've provided. You are running an endless loop in the form's constructor!! This means user inputs to the GUI will never be processed, indeed the GUI might not even appear at all. In my opinion anything involving an endless loop requires it's own thread.

Anyway, I have edited your code to demonstrate how you could use the TcpListener object in it's own thread.

Code:

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Net;
using System.Threading;
using System.Net.Sockets;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private List<Socket> clients = new List<Socket>();
        private Thread listening_thread;
        private TcpListener listener;

        public Form1()
        {
            InitializeComponent();

            this.listening_thread = new Thread(new ThreadStart(this.ListeningThread));
            this.listening_thread.Start();
        }

        private void ListeningThread() // let's listen in another thread instead!!
        {
            int port = 12345; // change as required

            this.listener = new TcpListener(IPAddress.Any, port);

            try
            {
                this.listener.Start();
            }
            catch (Exception e) { MessageBox.Show("couldn't bind to port " + port + " -> " + e.Message); return; }

            while (true)
            {
                if (this.listener.Pending())
                    this.clients.Add(this.listener.AcceptSocket()); // won't block because pending was true

                foreach (Socket sock in this.clients)
                    if (sock.Poll(0, SelectMode.SelectError))
                        clients.Remove(sock);
                    else if (sock.Poll(0, SelectMode.SelectRead))
                        ParserFunction(sock);

                Thread.Sleep(30);
            }
        }

        private void ParserFunction(Socket sock)
        {

        }
    }
}

Hope this helps.