import java.io.*; 
import java.net.*; 
 
/**
 * @author K&R
 * Simple example UDP server
 */
public class UDPServer
{
   public static void main(String args[]) throws Exception
   {
      int bufferLength = 1024;
      int listenPort = 9876;

      DatagramSocket serverSocket = new DatagramSocket( listenPort );

      byte[] receiveData = new byte[bufferLength];
      byte[] sendData; // = new byte[bufferLength];

      while (true)
      {
         
         System.out.println("Server listening to " + listenPort);

         DatagramPacket receivePacket =
            new DatagramPacket(receiveData, receiveData.length);
         serverSocket.receive(receivePacket);

         String sentence = new String(receivePacket.getData(), 0, receivePacket.getLength());

         InetAddress IPAddress = receivePacket.getAddress();

         int port = receivePacket.getPort();

         String capitalizedSentence = sentence.toUpperCase();

         sendData = capitalizedSentence.getBytes();

         DatagramPacket sendPacket =
            new DatagramPacket(sendData, sendData.length, IPAddress, port);

         serverSocket.send(sendPacket);
      }
   }
}