gistfile1.cs

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

namespace Client
{
    public partial class Form1 : Form
    {

        private static string ip = "192.168.0.100";
        private static short port = 8000;
        // end of config

        private static TcpClient client = new TcpClient();
        private static IPEndPoint endPoint = new IPEndPoint(IPAddress.Parse(ip), port);

        public Form1()
        {
            InitializeComponent();
            rtbInput.ReadOnly = true;
            try
            {
                client.Connect(endPoint);
            }

            catch
            {
                rtbInput.Text += "Could not connect to the server";
                return;
            }
        }

        private void btnSend_Click(object sender, System.EventArgs e){


            var stream = client.GetStream();
            string msg;
            byte[] buffer;

            // Send messages to the server
            while (true)
            {
                msg = tbOutput.Text;
                rtbInput.AppendText(msg + System.Environment.NewLine);
                if (!String.IsNullOrWhiteSpace(msg))
                {
                    buffer = Encoding.ASCII.GetBytes(msg);

                    stream.Write(buffer, 0, buffer.Length);
                    stream.Flush();
                    tbOutput.Clear();
                }
                else break;
            }
        }
    }
}

gistfile2.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace Server
{
    public partial class Form1 : Form
    {

        // config
        private static string ip = "192.168.0.100";
        private static short port = 8000;
        // end of config

        private static Thread thread;
        private static TcpListener listener;

        delegate void SetTextCallback(string text);

        public Form1()
        {
            InitializeComponent();
            rtbText.ReadOnly = true;
            listener = new TcpListener(IPAddress.Parse(ip), port);
            thread = new Thread(worker);

            // start the listening thread
            thread.Start();
        }

        public void worker()
        {

            // listen...
            listener.Start();

            SetText("Waiting for clients");

            while (true)
            {
                // wait for a client to connect
                TcpClient client = listener.AcceptTcpClient();

                // client connected
                int s = client.GetHashCode();
                SetText("Client " + s + " connected...");

                // launch a thread to handle it
                ThreadPool.QueueUserWorkItem(tcpClient =>
                {
                    var theClient = (TcpClient)tcpClient;
                    var stream = theClient.GetStream();

                    var bufferSize = 4096;
                    var buffer = new byte[bufferSize];
                    int count;

                    // read the client data
                    while (true)
                    {
                        count = 0;

                        try
                        {
                            count = stream.Read(buffer, 0, bufferSize);
                        }
                        catch (Exception ex)
                        {
                            SetText("Error while reading client data: " + ex.Message);
                            break;
                        }

                        if (count > 0)
                        {
                            int i = theClient.GetHashCode();
                            string m = Encoding.ASCII.GetString(buffer, 0, count);
                            SetText(i + " says: " + m);
                        }
                        else break;
                    }

                    stream.Close();
                    theClient.Close();

                }, client);
            }
        }

        private void SetText(string text)
        {
            if (this.rtbText.InvokeRequired)
            {
                SetTextCallback d = new SetTextCallback(SetText);
                this.Invoke(d, new object[] { text });
            }
            else
            {
                rtbText.AppendText(text + System.Environment.NewLine);
            }
        }

        private void btnSend_Click(object sender, EventArgs e)
        {

        }

    }
}