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();  }   }