Client-Server-Client communication using Sockets

Question

I am building a small chat application in which client A wants to send something to client C with server B in between. First of all is this a correct approach for the proble

Answer 1

When your clients connect to the server, your server creates a Socket for it, here it is Socket socket = ss.accept();, your socket variable will be holding that client.

now if you just keep adding your client socket to a arraylist in your while loop, you will have a list of clients actively connected with your server like:

after the accept:

clients = new ArrayList();
Socket socket = ss.accept();
os = new DataOutputStream(socket.getOutputStream());
clients.add(os);

Now as you have all the clients in that clients arraylist, you can loop through it, or with some protocol define which client should i send the data after reading.

Iterator it = clients.iterator();
while ((message = reader.readLine()) != null) { //reading    
    while (it.hasNext()) {
        try {
            DataOutputStream oss = it.next();
            oss.write(message);//writing
            oss.flush();
        }
        catch (Exception e) { }
     }
 }

This will loop through all the available clients in the arraylist and will send to all. you can define ways to send to only some.

For example: maintain a ActiveClients arraylist and with some GUI interaction may be or maybe, define what all clients you want to send the message. Then add just those clients outputStreams to ActiveClients

ActiveClients.add(clients.get(2));

or remove them, if you don't want them.

ActiveClients.remove(clients.get(2));

and now just loop through this arraylist to send the data as above.