UDPServer.java

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

public class UDPServer {

    public static void main(String args[]) throws Exception {

        DatagramSocket serverSocket = new DatagramSocket(9877);

        while (true) {

            byte[] receiveData = new byte[10];
            byte[] sendData = new byte[10];
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            serverSocket.receive(receivePacket);
            String sentence = new String(receivePacket.getData());
            System.out.println("From Client: " + sentence);
            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);
        }
    }
}