import java.net.*;
import java.io.*;
import java.util.*;
?
public class GroupChat {
?? ?private static final String TERMINATE = "Exit";
?? ?static String name;
?? ?static volatile boolean finished = false;
?
?? ?public static void main(String[] args) {
?? ??? ?if (args.length != 2)
?? ??? ??? ?System.out.println("Two arguments required: <multicast-host> <port-number>");
?? ??? ?else {
?? ??? ??? ?try {
?? ??? ??? ??? ?InetAddress group = InetAddress.getByName(args[0]);
?? ??? ??? ??? ?int port = Integer.parseInt(args[1]);
?? ??? ??? ??? ?Scanner sc = new Scanner(System.in);
?? ??? ??? ??? ?System.out.print("Enter your name: ");
?? ??? ??? ??? ?name = sc.nextLine();
?? ??? ??? ??? ?MulticastSocket socket = new MulticastSocket(port);
?
?? ??? ??? ??? ?// Since we are deploying
?? ??? ??? ??? ?socket.setTimeToLive(0);
?? ??? ??? ??? ?// this on localhost only (For a subnet set it as 1)
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?? ??? ??? ??? ?socket.joinGroup(group);
?? ??? ??? ??? ?Thread t = new Thread(new ReadThread(socket, group, port));
?
?? ??? ??? ??? ?// Spawn a thread for reading messages
?? ??? ??? ??? ?t.start();
?
?? ??? ??? ??? ?// sent to the current group
?? ??? ??? ??? ?System.out.println("Start typing messages...\n");
?? ??? ??? ??? ?while (true) {
?? ??? ??? ??? ??? ?String message;
?? ??? ??? ??? ??? ?message = sc.nextLine();
?? ??? ??? ??? ??? ?if (message.equalsIgnoreCase(GroupChat.TERMINATE)) {
?? ??? ??? ??? ??? ??? ?finished = true;
?? ??? ??? ??? ??? ??? ?socket.leaveGroup(group);
?? ??? ??? ??? ??? ??? ?socket.close();
?? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?message = name + ": " + message;
?? ??? ??? ??? ??? ?byte[] buffer = message.getBytes();
?? ??? ??? ??? ??? ?DatagramPacket datagram = new DatagramPacket(buffer, buffer.length, group, port);
?? ??? ??? ??? ??? ?socket.send(datagram);
?? ??? ??? ??? ?}
?? ??? ??? ?} catch (SocketException se) {
?? ??? ??? ??? ?System.out.println("Error creating socket");
?? ??? ??? ??? ?se.printStackTrace();
?? ??? ??? ?} catch (IOException ie) {
?? ??? ??? ??? ?System.out.println("Error reading/writing from/to socket");
?? ??? ??? ??? ?ie.printStackTrace();
?? ??? ??? ?}
?? ??? ?}
?? ?}
}
?
class ReadThread implements Runnable {
?? ?private MulticastSocket socket;
?? ?private InetAddress group;
?? ?private int port;
?? ?private static final int MAX_LEN = 1000;
?
?? ?ReadThread(MulticastSocket socket, InetAddress group, int port) {
?? ??? ?this.socket = socket;
?? ??? ?this.group = group;
?? ??? ?this.port = port;
?? ?}
?
?? ?@Override
?? ?public void run() {
?? ??? ?while (!GroupChat.finished) {
?? ??? ??? ?byte[] buffer = new byte[ReadThread.MAX_LEN];
?? ??? ??? ?DatagramPacket datagram = new DatagramPacket(buffer, buffer.length, group, port);
?? ??? ??? ?String message;
?? ??? ??? ?try {
?? ??? ??? ??? ?socket.receive(datagram);
?? ??? ??? ??? ?message = new String(buffer, 0, datagram.getLength(), "UTF-8");
?? ??? ??? ??? ?if (!message.startsWith(GroupChat.name))
?? ??? ??? ??? ??? ?System.out.println(message);
?? ??? ??? ?} catch (IOException e) {
?? ??? ??? ??? ?System.out.println("Socket closed!");
?? ??? ??? ?}
?? ??? ?}
?? ?}
}