// second dummy version of dglistener5 in Java

// three classes in the same file

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

// main class, just starts listener and ui
public class Dglistener5 {

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

		int port = 54321;
		if (args.length > 0) {
			port = Integer.valueOf(args[0]);
			if (port < 1024)
				port = 54321;
		}

		Dglistener5Thread net = new Dglistener5Thread(port);
		net.start();
		new Dglistener5UI(net).start();
	} // main()

} // class Dglistener5


// thread to listen for the socket
class Dglistener5Thread extends Thread {

	protected DatagramSocket socket;
	protected String message;
	protected int port;

	public Dglistener5Thread(int p) {
		super();
		port = p;
	}


	public void run() {

		try {

			socket = new DatagramSocket(port);
			byte[] rbuf = new byte[1000];

			message = "Hello";

			String knownhosts = new String();

			System.out.println("Socket listening port " + port);


			while(true) {

				// receive
				DatagramPacket rpacket = new DatagramPacket(rbuf, rbuf.length);
				socket.receive(rpacket);

				System.out.println("Got message from " +
								   rpacket.getAddress() + " port " +
								   rpacket.getPort());

				// getAddress() prefixes address with a /, strip it away
				String newhost = rpacket.getAddress().toString().substring(1) +
					":" + rpacket.getPort();

				if (knownhosts.indexOf(newhost) == -1) {
					System.out.println("New host");
					knownhosts = knownhosts + " " + newhost;
				} else
					System.out.println("Old host");


				// construc reply
				String response = message + " Known hosts are:" + knownhosts;

				byte[] sbuf = response.getBytes();

				DatagramPacket spacket = new DatagramPacket(sbuf, sbuf.length,
															rpacket.getAddress(), rpacket.getPort());
				socket.send(spacket);
			} // while

		} catch (SocketException e) {
			System.err.println("socket problem" + e);
		} catch (IOException e) {
			System.err.println("io problem" + e);
		}

	} // run()

	// change message
	public void setMessage(String msg) {
		message = msg;
	}

} // class Dglistener5Thread


// User interface
class Dglistener5UI extends Thread {

	Dglistener5Thread net;

	public Dglistener5UI(Dglistener5Thread n) {
		super();
		net = n;
	}

	public void run() {
		String line = new String();

		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

		System.out.println("UI ready");
		while(true) {
			try {
				line = in.readLine();
			}  catch (IOException e) {
				System.err.println("input" + e);
			}
			if (line.indexOf("quit") != -1) {
				// if you want to kill net thread cruely, uncomment:
				// net.stop();
				// but stop() is a deprecated method
				return;

			} else
				net.setMessage(line);
		}

	} // run()

} // class Dglistener5UI