import java.net.*;

public class EchoServer  {
	
	static final int ECHOPORT = 8000;
	static final int MAXBLOCKSIZE = 1460 ;
	
	public static void main(String[] args) throws Exception {
		// create input / output UDP socket and bind it to the ECHOPORT
		DatagramSocket socket = new DatagramSocket( ECHOPORT ) ;
		// prepare a datagram, for receiving and sending
		DatagramPacket datagram = new DatagramPacket( new byte[MAXBLOCKSIZE],
		        MAXBLOCKSIZE ) ;
		for(;;) { // server endless loop
			System.out.println( "Echo server ready");
			socket.receive( datagram );	
			System.out.printf("Got: %s \n", 
			    new String( datagram.getData(), 0, datagram.getLength()));
			//prepare an UDP datagram with the reply
			// the port and IP address associated with the datagram are the ones
			// of the sender when a datagram is received and are used as the
			// IP address and port of the destination when the datagram is sent
			socket.send( datagram ) ;
			datagram.setLength(MAXBLOCKSIZE); // since the payload may have shrunk 
		} // endless loop
	} // main
} // EchoServer