package udps;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Level;
import java.util.logging.Logger;

public class UDPServer {

    public static void main(String[] args) {
        UDPServer server = new UDPServer();
        server.init();
    }
    
    public void init() {
        Thread serverThread = new Thread(new Server());
        serverThread.start();
    }

    public class Server implements Runnable {

        public void run() {
            DatagramSocket socket = null;
            
            try {
                socket = new DatagramSocket(7777);
            } catch (SocketException ex) {
                Logger.getLogger(UDPServer.class.getName()).log(Level.SEVERE, null, ex);
            }
            
            ExecutorService pool = Executors.newFixedThreadPool(32);

            for (;;) {
                DatagramPacket packet = new DatagramPacket(new byte[1024], 1024);
                
                try {
                    socket.receive(packet);
                } catch (IOException ex) {
                    Logger.getLogger(UDPServer.class.getName()).log(Level.SEVERE, null, ex);
                }
                
                pool.execute(new Responder(socket, packet));
            }
        }
    }

    public class Responder implements Runnable {

        DatagramSocket socket = null;
        DatagramPacket packet = null;

        public Responder(DatagramSocket socket, DatagramPacket packet) {
            this.socket = socket;
            this.packet = packet;
        }

        public void run() {
            byte[] data = "PONG".getBytes();
            
            DatagramPacket response = new DatagramPacket(data, data.length, packet.getAddress(), packet.getPort());
            
            System.out.println(packet.getData().toString());
            
            try {
                socket.send(response);
            } catch (IOException ex) {
                Logger.getLogger(UDPServer.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }
}