Socket - Send info to all clients?

Question

Hi I've tried the Sockets Tutorial on Sun and found it really great but one thing. It leaves out the idea of all clients being in touch with each other.
import java.io.*;
import java.net.*;
public class KnockKnockClient {
    public static void main(String[] args) throws IOException {
         Runtime.getRuntime().exec("java KKMultiServer");
        Socket kkSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
        try {
            kkSocket = new Socket("213.67.113.48"/*my IP*/, 4444);
               System.out.println(kkSocket);
            out = new PrintWriter(kkSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
        } catch (UnknownHostException e) {
              System.out.println(e);
            System.exit(1);
        } catch (IOException e) {
            System.err.println(e);
            System.exit(1);
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        String fromServer;
        String fromUser;
        while ((fromServer = in.readLine()) != null) {
            System.out.println("Server: " + fromServer);
            if (fromServer.equals("Bye."))
                break;
            fromUser = stdIn.readLine();
         if (fromUser != null) {
                System.out.println("Client: " + fromUser);
                 //Send info to server thread
                out.println(fromUser);
        out.close();
        in.close();
        stdIn.close();
        kkSocket.close();
import java.net.*;
import java.io.*;
public class KKMultiServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;
        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println(e);
            System.exit(-1);
        while (listening)
                  //Starts a new thread for each client that connects to the port
            new KKMultiServerThread(serverSocket.accept()).start();
        serverSocket.close();
import java.net.*;
import java.io.*;
public class KKMultiServerThread extends Thread {
    private Socket socket = null;
    public KKMultiServerThread(Socket socket) {
     super("KKMultiServerThread");
     this.socket = socket;
     System.out.println(socket);
    public void run() {
     try {
         PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            //Gets what the client writes
         BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
         String inputLine, outputLine;
         KnockKnockProtocol kkp = new KnockKnockProtocol();
         outputLine = kkp.processInput(null);
             //Send back to client
             //This I would like to send to all clients and not just the one who wrote to the server
         out.println(outputLine);
         while ((inputLine = in.readLine()) != null) {
          outputLine = kkp.processInput(inputLine);
                 //Send back to client
                //This I would like to send to all clients and not just the one who wrote to the server
          out.println(outputLine);
          if (outputLine.equals("Bye"))
              break;
         out.close();
         in.close();
         socket.close();
     } catch (IOException e) {
         e.printStackTrace();
import java.net.*;
import java.io.*;
public class KnockKnockProtocol {
    private static final int WAITING = 0;
    private static final int SENTKNOCKKNOCK = 1;
    private static final int SENTCLUE = 2;
    private static final int ANOTHER = 3;
    private static final int NUMJOKES = 5;
    private int state = WAITING;
    private int currentJoke = 0;
    private String[] clues = { "Turnip", "Little Old Lady", "Atch", "Who", "Who" };
    private String[] answers = { "Turnip the heat, it's cold in here!",
                                 "I didn't know you could yodel!",
                                 "Bless you!",
                                 "Is there an owl in here?",
                                 "Is there an echo in here?" };
    public String processInput(String theInput) {
        String theOutput = null;
        if (state == WAITING) {
            theOutput = "Knock! Knock!";
            state = SENTKNOCKKNOCK;
        } else if (state == SENTKNOCKKNOCK) {
            if (theInput.equalsIgnoreCase("Who's there?")) {
                theOutput = clues[currentJoke];
                state = SENTCLUE;
            } else {
                theOutput = "You're supposed to say \"Who's there?\"! " +
                   "Try again. Knock! Knock!";
        } else if (state == SENTCLUE) {
            if (theInput.equalsIgnoreCase(clues[currentJoke] + " who?")) {
                theOutput = answers[currentJoke] + " Want another? (y/n)";
                state = ANOTHER;
            } else {
                theOutput = "You're supposed to say \"" +
                   clues[currentJoke] +
                   " who?\"" +
                   "! Try again. Knock! Knock!";
                state = SENTKNOCKKNOCK;
        } else if (state == ANOTHER) {
            if (theInput.equalsIgnoreCase("y")) {
                theOutput = "Knock! Knock!";
                if (currentJoke == (NUMJOKES - 1))
                    currentJoke = 0;
                else
                    currentJoke++;
                state = SENTKNOCKKNOCK;
            } else {
                theOutput = "Bye.";
                state = WAITING;
        return theOutput;
}As you see I wrote in commented that I'd like the Thread to send the String to all connected clients, is that possible? If so please tell me how this can be done.
//Thanks Considerate

Answer 1

Hi I've tried the Sockets Tutorial on Sun and found it really great but one >thing. It leaves out the idea of all clients being in touch with each other.Consider that the clients could receive data like jwenting says below which means all traffic MUST be routed through the server
OR you could also have the client open a Socket directly to the other client
and send the data sans server.
georgemc>     
Look into multicasting (google is your friend)Unless he wants guaranteed delivery.
sabre150>
but don't expect it to work for clients outside of your intranet.This is true and depending on your router you may not be able to implement a class D address.
jwenting>
So better keep a list of connected clients and loop through that to send the >notifications. Bingo!
(T)