import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.util.Scanner;

public class SendDemo {

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

        while (true) {

            System.out.print("Please input data:");

            byte[] say = new Scanner(System.in).nextLine().getBytes();

            DatagramSocket ds = new DatagramSocket();

            DatagramPacket dp = new DatagramPacket(say, say.length,

                    InetAddress.getByName("127.0.0.1"), 1357);

            ds.send(dp);

        }

    }

}

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

public class ReceiveDemo {

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

        DatagramSocket ds = new DatagramSocket(1357);

        while (true) {

            byte[] buf = new byte[2048];

            DatagramPacket dp = new DatagramPacket(buf, buf.length);

            ds.receive(dp);

            System.out.println("from:" + dp.getAddress().getHostName()

                    + " message:"

                    + new String(dp.getData(), 0, dp.getData().length));

        }

    }

}