A Group chat application in Java

A Group chat application in Java
In this post, a group chat application using MulticastSocket (Java Platform SE 7) class is discussed. A MulticastSocket is a (UDP) DatagramSocket, with additional capabilities for joining “groups” of other multicast hosts on the internet.

Implementation

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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)

                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!");
            }
        }
    }
}
Save the file as GroupChat.java and compile it using javac and then run the program using two command line arguments as specified. A multicast host is specified by a class D IP address and by a standard UDP port number. Class D IP addresses are in the range 224.0.0.0 to 239.255.255.255, inclusive. The address 224.0.0.0 is reserved and should not be used.
For more information visit this site:
https://www.youtube.com/channel/UCJ0nVqHF9lBebRXugUOin4A