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


class UDPserver
{
final static int ECHO_PORT=7;
public static void main(String args[])
{
DatagramSocket ds;
DatagramPacket dp;

try{
ds=new DatagramSocket(ECHO_PORT);
while(true){
dp=new DatagramPacket(new byte[1024],1024);
ds.receive(dp);
dp=new DatagramPacket(dp.getData(),
dp.getLength(),dp.getAddress(),dp.getPort());
ds.send(dp);
}
}catch(IOException e){
System.out.println("could not recieve or send data");
}
}
}