A simple TCP listener. Assumes you're sending UTF8 text to it.

TcpListener.cs

using System;
using System.IO;
using System.Net;
using System.Text;

namespace TcpListener
{
    class Program
    {
        static void Main(string[] args)
        {
            byte[] receiveBuffer = new byte[65536];
            var listener = new System.Net.Sockets.TcpListener(IPAddress.Any, 5151);

            listener.Start();
            Console.WriteLine("Started.........");
            while (true)
            {
                using (var tcpClient = listener.AcceptTcpClient())
                {
                    Console.WriteLine("got a connection...");
                    using (var stream = tcpClient.GetStream())
                    {
                        while (tcpClient.Connected)
                        {
                            try
                            {
                                var bytes = stream.Read(receiveBuffer, 0, tcpClient.ReceiveBufferSize);
                                if (bytes == 0) break;
                                Console.WriteLine(Encoding.UTF8.GetString(receiveBuffer, 0, bytes));
                            }
                            catch (IOException)
                            {
                                break;
                            }
                        }
                    }
                }
            }
        }
    }
}