import java.net.*;
import java.io.*;
import java.util.*;

class ChatServer {
    protected Hashtable users = new Hashtable();
    protected ServerSocket server;

    public static void main(String[] args) throws IOException {
        ChatServer cs = new ChatServer(8080);
        cs.accept();
    }

    public ChatServer(int port) {
        // create a server listening at port, max 15 pending connections
        try {
            // ### create server socket attached to port
            server = ... ;

        }
        catch (IOException e) {
            System.err.println("cannot listen at "+port+
                   " ("+e.getMessage()+")");
        }
    }

    public void accept() {
        System.out.println("ChatServer listening...");
        Socket socket = null;
        while (true) {
            // For each connection, start a new client handler
            // in its own thread and keep on listening
            try {
                socket = server.accept();
                // ### create ClientHandler attached to this, socket
                // ### create thread attach to handler
                // ### launch thread
            }
            catch (IOException e) {
                System.err.println("Error creating socket connection");
                System.exit(1);
            }
        }
    }

    // S U P P O R T  R O U T I N E S

    /** Track that this user name has this output stream */
    public void registerClient(String user, PrintStream out) {
        broadcast(user, "connected");
        users.put(user, out);
    }

    /** Send a string to everybody but user */
    public void broadcast(String user, String line) {
        Enumeration e = users.keys();
        while ( e.hasMoreElements() ) {
            String u = (String)e.nextElement();
            if ( !u.equals(user) ) {
                PrintStream out = (PrintStream)users.get(u);
                out.println(user+": "+line);
            }
        }
    }

    public void disconnect(String user) {
        users.remove(user);
        broadcast(user, "disconnected");
    }
}