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();

  }

}