using System;
  using System.IO;
  using System.Net;
  using System.Net.Sockets;
  using System.Text;
  class MyTcpListener
  {
    public static void Main()
    {
        TcpListener server = null;
        try
        {
            // Set the TcpListener on port 13000.
            Int32 port = 13000;
            IPAddress localAddr = IPAddress.Parse("127.0.0.1");
            // TcpListener server = new TcpListener(port);
            server = new TcpListener(localAddr, port);
            // Start listening for client requests.
            server.Start();
            // Buffer for reading data
            Byte[] bytes = new Byte[256];
            String data = null;
            // Enter the listening loop. 
            while (true)
            {
                Console.Write("Waiting for a connection... ");
                // Perform a blocking call to accept requests. 
                // You could also user server.AcceptSocket() here.
                TcpClient client = server.AcceptTcpClient();
                Console.WriteLine("Connected!");
                data = null;
                // Get a stream object for reading and writing
                NetworkStream stream = client.GetStream();
                int i;
                // Loop to receive all the data sent by the client. 
                while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
                {
                    // Translate data bytes to a ASCII string.
                    data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
                    Console.WriteLine("Received: {0}", data);
                    // Process the data sent by the client.
                    data = data.ToUpper();
                    byte[] msg = System.Text.Encoding.ASCII.GetBytes(data);
                    // Send back a response.
                    stream.Write(msg, 0, msg.Length);
                    Console.WriteLine("Sent: {0}", data);
                }
                // Shutdown and end connection
                client.Close();
            }
        }
        catch (SocketException e)
        {
            Console.WriteLine("SocketException: {0}", e);
        }
        finally
        {
            // Stop listening for new clients.
            server.Stop();
        }
        Console.WriteLine("\nHit enter to continue...");
        Console.Read();
    }
  }