::::::::::::::
ChatApplet.java
::::::::::::::
import java.applet.*; 
import java.awt.*; 
import java.awt.event.*; 

public class ChatApplet extends Applet implements ActionListener {

    public void actionPerformed(ActionEvent event) {
	try {
	    String cmd = event.getActionCommand(); 
	    Update alpha = new Update(owner.getClientName(), cmd, null); 
	    owner.broadcast(alpha); 
	} catch (Exception e) {

	}
    }

    ChatFrame owner; 

    public void setOwner(ChatFrame chatFrame) {
	this.owner = chatFrame; 
    }

    TextArea textArea;
    TextField textField; 
    DrawPad drawPad; 
    Button list, clearDraw, clearText;

    public void init() {
	this.setLayout(new BorderLayout()); 
	Panel panel = new Panel(); 
	panel.setLayout(new FlowLayout()); 
	panel.add(list = new Button("List")); 
	panel.add(clearDraw = new Button("ClearDraw")); 
	panel.add(clearText = new Button("ClearText")); 
	Button disconnect = new Button("disconnect"); 
	disconnect.setBackground(Color.pink); 
	panel.add(disconnect);
	textArea = new TextArea(4, 40);
	textArea.setEditable(false);
	textField = new TextField(40);
	drawPad = new DrawPad(this);
	drawPad.setSize(400, 400);
	add(drawPad, "East");
	add(textArea, "Center");
	add(textField, "South");
	add(panel, "North");
	textField.addActionListener(this);
	list.addActionListener(this);
	clearDraw.addActionListener(this);
	clearText.addActionListener(this);
	disconnect.addActionListener(this);
    }

    public void showText(String sender, String message) {
	this.textArea.append(sender + message + "\n"); 
	this.textField.setText(""); 
    }

    public void clearText() {
	this.textArea.setText(""); 
	this.textField.setText(""); 
    }
}



::::::::::::::
ChatFrame.java
::::::::::::::
import java.awt.*; 
import java.rmi.*; 

public class ChatFrame extends Frame {
    ClientImplementation client; 
    ChatApplet chatApplet; 
    public ChatFrame(ClientImplementation client) {
	super(); 
	this.client = client; 
	this.chatApplet = new ChatApplet(); 
        this.chatApplet.setOwner(this); 
	this.chatApplet.init(); 
	this.add(this.chatApplet, "Center"); 
    }
    public void broadcast(Update event) {
	try { 
	    this.client.getServer().broadcast(event);
	} catch (Exception e) {

	}
    }
    public String getClientName() {
	return this.client.name; 
    }
}
::::::::::::::
Client.java
::::::::::::::
import java.rmi.*; 

public interface Client extends Remote {
    public void update(Update event) throws RemoteException; 
    public String name() throws RemoteException; 
    public void setId(int id) throws RemoteException; 
    public void setServer(Server server) throws RemoteException; 
}
::::::::::::::
ClientImplementation.java
::::::::::::::
import java.rmi.*; 
import java.awt.event.*; 

public class ClientImplementation implements Client {
    String name; 
    int id; 

    Server server; 

    public Server getServer() {
	return server; 
    }

    ChatFrame chatFrame; 

    public ClientImplementation(String name) {
	this.name = name; 
	this.chatFrame = new ChatFrame(this); 
        chatFrame.setSize(820, 600); 
	chatFrame.show(); 
	chatFrame.addWindowListener(
	    new WindowAdapter() {
	        public void windowClosing(WindowEvent e) { System.exit(0); }
	    }
        ); 
    }

    public void update(Update event) throws RemoteException {

	if (event.line != null) 
	    chatFrame.chatApplet.drawPad.receive(event.line);

	if (event.message != null) {

	    if (event.message.equals("ClearDraw")) {
		chatFrame.chatApplet.drawPad.clearScreen();
		this.chatFrame.chatApplet.textField.setText("");
	    } else if (event.message.equals("ClearText")) {
		chatFrame.chatApplet.clearText();
	    } else if (event.message.equals("List")) {
		chatFrame.chatApplet.showText
		    (event.sender + " is listing: \n", server.list());
	    } else { // basic message 
		chatFrame.chatApplet.showText
		    (event.sender + ": ", event.message);
	    }
	}
    }

    public String name() throws RemoteException {
	return this.name; 
    }

    public void setId(int id) throws RemoteException {
	this.id = id; 
	System.out.println(this.name + ": my id is " + this.id); 
    }

    public void setServer(Server server) throws RemoteException {
	this.server = server; 
    }


}
::::::::::::::
DrawPad.java
::::::::::::::
import java.awt.*; 
import java.awt.event.*; 
import java.util.*; 

public class DrawPad extends Canvas implements MouseMotionListener, 
					       MouseListener {

  Vector lines = new Vector(); 

  ChatApplet applet; 

  public DrawPad(ChatApplet applet) {
    this.applet = applet;     
    addMouseMotionListener(this); 
    addMouseListener(this); 
  }

  int startX, startY; 

  public void mouseDragged(MouseEvent event) { 
    Line line = new Line(startX, startY, event.getX(), event.getY()); 
    startX = event.getX(); startY = event.getY(); 
    Update update = new Update(applet.owner.client.name, null, line); 
    try { 

      applet.owner.broadcast(update); 

    } catch (Exception exception) { } 

  } 

  public void receive(Line line) {
    lines.addElement(line); 
    this.render(line); 
  }

  public void clearScreen() {
    this.lines = new Vector(); 
    Graphics g = this.getGraphics(); 
    this.repaint(); 
  }

  public void render(Line line) {
    this.getGraphics().drawLine(line.x0, line.y0, line.x1, line.y1); 
  }

  public void mouseMoved(MouseEvent e) { } 
  public void mousePressed(MouseEvent e) {  
    startX = e.getX(); 
    startY = e.getY(); 
  } 

  public void mouseReleased(MouseEvent e) { } 

  public void mouseClicked(MouseEvent e) { } 

  public void mouseEntered(MouseEvent e) { }

  public void mouseExited(MouseEvent e) { } 

  public void paint(Graphics g) {
    if (lines != null) { 
      for (int i = 0; i < lines.size(); i++) {
        this.render((Line)lines.elementAt(i));    
      }
    }   
  }

}
::::::::::::::
Line.java
::::::::::::::
import java.io.*; 

public class Line implements Serializable {
    int x0, y0, x1, y1; 
    public Line(int x0, int y0, int x1, int y1) {
	this.x0 = x0; 
        this.y0 = y0; 
	this.x1 = x1; 
	this.y1 = y1; 
    }
}
::::::::::::::
NetworkClient.java
::::::::::::::
import java.rmi.*;
import java.rmi.server.*;

public class NetworkClient extends ClientImplementation
                           implements Client {

  public NetworkClient(String name) throws RemoteException {
    super(name);
    UnicastRemoteObject.exportObject(this);
  }

  public static void main(String[] args) {
    try {
      Server far =
        (Server)Naming.lookup(
          "rmi://" + args[0] + ":" + args[1] + "/Dirac");

      NetworkClient here = new NetworkClient(args[2]);

      here.setId(far.register(here)); 
      here.setServer(far); 
      // here.start();

    } catch (Exception e) {
      System.out.println("Error in client... " + e);
      e.printStackTrace();
    }

  }

}
::::::::::::::
NetworkServer.java
::::::::::::::
import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.*;

public class NetworkServer extends ServerImplementation
                           implements Server {

  public NetworkServer() throws RemoteException {
    UnicastRemoteObject.exportObject(this);
    System.out.println("Server being initialized... ");
  }

  public static void main(String[] args) {
    System.setSecurityManager(new RMISecurityManager());
    try {
      NetworkServer pam = new NetworkServer();
      Registry cat =
        LocateRegistry.createRegistry(Integer.parseInt(args[0]));

      cat.bind("Dirac", pam);

      System.out.println("Server is ready... ");
    } catch (Exception e) {
      System.out.println("Server error: " + e + "... ");
    }

  }

}

::::::::::::::
Server.java
::::::::::::::
import java.rmi.*; 

public interface Server extends Remote {
    public int register(Client client) throws RemoteException; 
    public void broadcast(Update event) throws RemoteException; 
    public String list() throws RemoteException; 
}
::::::::::::::
ServerImplementation.java
::::::::::::::
import java.rmi.*; 

public class ServerImplementation implements Server {

    Client clients[] = new Client[100]; 

    int index = -1; 

    public int register(Client client) throws RemoteException {
	clients[++index] = client; 
	return index; 
    }

    public void broadcast(Update event) throws RemoteException {
	for (int i = 0; i <= index; i++) 
            clients[i].update(event); 
    }

    public String list() throws RemoteException {
	String result = "";
        for (int i = 0; i <= index; i++) 
	    result += "  ***(" + clients[i].name() + ")***  \n"; 
	return result;
    }

}
::::::::::::::
Simulation.java
::::::::::::::
import java.rmi.*; 

public class Simulation {
    public static void main(String[] args) throws RemoteException {

        ServerImplementation server = new ServerImplementation(); 

	Server far = server; 

	ClientImplementation one = new ClientImplementation("One"); 
	one.setId(far.register(one));  
	one.setServer(far); 

	ClientImplementation two = new ClientImplementation("Two"); 
	two.setId(far.register(two)); 
	two.setServer(far);

    }
}
::::::::::::::
Update.java
::::::::::::::
import java.io.*; 

public class Update implements Serializable {
    String sender; 
    String message; 
    Line line; 
    public Update(String sender, String message, Line line) {
	this.sender = sender; 
	this.message = message; 
	this.line = line; 
    }
    public String toString() {
	return sender + ": " + message + " " + line; 
    }
}