TCPThreadServer

import java.io.*;
import java.net.*;
import java.util.*;

public class TCPThreadServer {

    private static ServerSocket serverSocket;
    private static final int PORT = 9393;
    public static void main(String[] args)
            throws IOException
    {
        System.out.println("Opening port...\n");
        try
        {
            serverSocket = new ServerSocket(PORT);
        }
        catch (IOException ioEx)
        {
            System.out.println("\nUnable to set up port!");
            System.exit(1);
        }
        do
        {
            //Wait for client...
            Socket client = serverSocket.accept();

            System.out.println("\nNew client accepted.\n");

            //Create a thread to handle communication with
            //this client and pass the constructor for this
            //thread a reference to the relevant socket...
            ClientHandler handler =
                    new ClientHandler(client);
            handler.start();//As usual, method calls run.
        }while (true);
    }
}

class ClientHandler extends Thread
{
    private Socket client;
    private Scanner input;
    private PrintWriter output;

   public ClientHandler(Socket socket)
   {
       //Set up reference to associated socket...
       client = socket;
      try
      {
          input = new Scanner(client.getInputStream());
          output = new PrintWriter(
                  client.getOutputStream(),true);
      }
      catch(IOException ioEx)
              {
                  ioEx.printStackTrace();
              }
   }
   public void run()
   {
       String message;

      do
      {
         //Accept message from client on
          //the socket's input stream...
          message = input.nextLine();

         //Echo message back to client on
         //the socket's output stream...
         output.println("ECHO: " + message);

         //Repeat above until 'QUIT' sent by client...
      }while (!message.equals("QUIT"));

      try
      {
          if (client!=null)
          {
              System.out.println(
                      "Closing down connection...");
              client.close();
          }
      }
      catch(IOException ioEx)
      {
          System.out.println("Unable to disconnect!");
      }
   }
}