import java.io.*;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;


public class DatagramServer {

    public static final int PORT = 8200;
    private DatagramSocket socket = null;
    DatagramPacket cerere, raspuns = null;

    public void start() throws IOException {
        socket = new DatagramSocket(PORT);
        try {
            while (true) {

                byte[] buf = new byte[256];
                cerere = new DatagramPacket(buf, buf.length);
                System.out.println(" Asteptam un pachet ... ");
                socket.receive(cerere);

                InetAddress adresa = cerere.getAddress();
                int port = cerere.getPort();

                String mesaj = " Hai " + new String(cerere.getData());
                buf = mesaj.getBytes();


                raspuns = new DatagramPacket(buf, buf.length, adresa, port);
                socket.send(raspuns);
            }
        } finally {
            if (socket != null)
                socket.close();
        }
    }

    public static void main(String[] args) throws IOException {
        new DatagramServer().start();
    }
}