I have to develop a whiteboard application in which both the local user and the remote user should be able to draw simultaneously, is this possible? If possible then any logic?

I have already developed a code but in which i am not able to do this, when the remote user starts drawing the shape which i am drawing is being replaced by his shape and co-ordinates. This problem is only when both draw simultaneously.

any idea guys?

Here is my code

class  Paper extends JPanel implements MouseListener,MouseMotionListener,ActionListener
{
    static BufferedImage image;
    int bpressed;
    Color color;
    Point start;
    Point end;
    Point mp;
    Button elipse=new Button("elipse");
    Button rectangle=new Button("rect");
    Button line=new Button("line");
    Button empty=new Button("");
    JButton save=new JButton("Save");
    JButton erase=new JButton("Erase");
    String selected;
    int ex,ey;//eraser
    DatagramSocket dataSocket;
    JButton button = new JButton("test");
    Client client;
    Point p=new Point();
    int w,h;
    public Paper(DatagramSocket dataSocket) 
    {        
        this.dataSocket=dataSocket;
        client=new Client(dataSocket);
        System.out.println("paper");
        setBackground(Color.white);
        addMouseListener(this);
        addMouseMotionListener(this);
        color = Color.black; 
        setBorder(BorderFactory.createLineBorder(Color.black));         
        //save.setPreferredSize(new Dimension(100,20));
        save.setMaximumSize(new Dimension(75,27));
        erase.setMaximumSize(new Dimension(75,27));
    }

    public  void paintComponent(Graphics g) 
    {
        try
        {
        g.drawImage(image, 0, 0, this);
        Graphics2D g2 = (Graphics2D)g;
        g2.setPaint(Color.black);
        if(selected==("elipse"))
            g2.drawOval(start.x, start.y,(end.x-start.x),(end.y-start.y));
        else if(selected==("rect"))
            g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y));
        else if(selected==("line"))
            g2.drawLine(start.x,start.y,end.x,end.y);
        }
        catch(Exception e)
        {}
        }
    //Function to draw the shape on image
    public void draw()
    {
      Graphics2D g2 = image.createGraphics();
      g2.setPaint(color);
      if(selected=="line")
            g2.drawLine(start.x, start.y, end.x, end.y);
      if(selected=="elipse")
            g2.drawOval(start.x, start.y, (end.x-start.x),(end.y-start.y));
      if(selected=="rect")
            g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y));
      repaint();
      g2.dispose();
      start=null;
    } 

    //To add the point to the board which is broadcasted by the server  
    public  synchronized void addPoint(Point ps,String varname,String shape,String event) 
    {
        try
        {
            if(end==null)
                end = new Point();
            if(start==null)
                start = new Point();
            if(shape.equals("elipse"))
                selected="elipse";
            else if(shape.equals("line"))
                selected="line";
            else if(shape.equals("rect"))
                selected="rect";
            else if(shape.equals("erase"))
            {
                selected="erase";
                erase();
            }
            if(end!=null && start!=null)
            {
                if(varname.equals("end"))
                        end=ps;
                if(varname.equals("mp"))
                        mp=ps;          
                if(varname.equals("start"))
                        start=ps;
                if(event.equals("drag"))
                       repaint();
                else if(event.equals("release"))
                        draw();
        }
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }
} 
    //To set the size of the image
    public void setWidth(int x,int y)
    {
        System.out.println("("+x+","+y+")");
        w=x;
        h=y;
        image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
         Graphics2D g2 = image.createGraphics();
         g2.setPaint(Color.white);
         g2.fillRect(0,0,w,h);
         g2.dispose();
    }

    //Function which provides the erase functionality
    public void erase() 
    {
        Graphics2D pic=(Graphics2D) image.getGraphics();
        pic.setPaint(Color.white);
        pic.fillRect(start.x, start.y, 10, 10);
    }

    //Function to add buttons into the panel, calling this function returns a panel  
    public JPanel addButtons()
    {
        JPanel buttonpanel=new JPanel();
        JPanel row1=new JPanel();
        JPanel row2=new JPanel();
        JPanel row3=new JPanel();
        JPanel row4=new JPanel();
        buttonpanel.setPreferredSize(new Dimension(80,80));

        //buttonpanel.setMinimumSize(new Dimension(150,150));
        row1.setLayout(new BoxLayout(row1,BoxLayout.X_AXIS));
        row1.setPreferredSize(new Dimension(150,150));
        row2.setLayout(new BoxLayout(row2,BoxLayout.X_AXIS));
        row3.setLayout(new BoxLayout(row3,BoxLayout.X_AXIS));
        row4.setLayout(new BoxLayout(row4,BoxLayout.X_AXIS));
        buttonpanel.setLayout(new BoxLayout(buttonpanel,BoxLayout.Y_AXIS));

        elipse.addActionListener(this);
        rectangle.addActionListener(this);
        line.addActionListener( this);
        save.addActionListener( this);
        erase.addActionListener( this);

        buttonpanel.add(Box.createRigidArea(new Dimension(10,10)));
        row1.add(elipse);
        row1.add(Box.createRigidArea(new Dimension(5,0)));
        row1.add(rectangle);
        buttonpanel.add(row1);
        buttonpanel.add(Box.createRigidArea(new Dimension(10,10)));

        row2.add(line);
        row2.add(Box.createRigidArea(new Dimension(5,0)));
        row2.add(empty);
        buttonpanel.add(row2);
        buttonpanel.add(Box.createRigidArea(new Dimension(10,10)));

        row3.add(save);
        buttonpanel.add(row3);
        buttonpanel.add(Box.createRigidArea(new Dimension(10,10)));

        row4.add(erase);
        buttonpanel.add(row4);
        return buttonpanel;
    }
    //To save the image drawn
    public void save()
    {
        try 
        {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
            JFileChooser fc = new JFileChooser();
            fc.showSaveDialog(this);        
            encoder.encode(image);
            byte[] jpgData = bos.toByteArray();
            FileOutputStream fos = new FileOutputStream(fc.getSelectedFile()+".jpeg");
            fos.write(jpgData);
            fos.close();
        //add replce confirmation here

        } 
        catch (IOException e) 
        {           
            System.out.println(e);
        }
    }
    public void mouseClicked(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void mouseEntered(MouseEvent arg0) {

    }
    public void mouseExited(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }
    public void mousePressed(MouseEvent e) 
    {
            if(selected=="line"||selected=="erase")
            {
                start=e.getPoint();
                client.broadcast(start,"start", selected,"press");
            }
            else if(selected=="elipse"||selected=="rect")
            {
                mp = e.getPoint();
                client.broadcast(mp,"mp", selected,"press");
            }
    }
    public void mouseReleased(MouseEvent e) 
    {
        if(start!=null)
        {
            if(selected=="line")
            {
                end=e.getPoint();           
                client.broadcast(end,"end", selected,"release");
            }
            else if(selected=="elipse"||selected=="rect")
            {
                end.x = Math.max(mp.x,e.getX());
                end.y = Math.max(mp.y,e.getY());
                client.broadcast(end,"end", selected,"release");
            }
            draw();
        }
    //start=null;
    }
    public void mouseDragged(MouseEvent e) 
    {
        if(end==null)
            end = new Point();

        if(start==null)
                start = new Point();

         if(selected=="line")
         {
            end=e.getPoint();
            client.broadcast(end,"end", selected,"drag");
         }
        else if(selected=="erase")
        {
             start=e.getPoint();
             erase();
            client.broadcast(start,"start", selected,"drag");
        }
        else if(selected=="elipse"||selected=="rect")
        {
            start.x = Math.min(mp.x,e.getX());
            start.y = Math.min(mp.y,e.getY());
            end.x = Math.max(mp.x,e.getX());
            end.y = Math.max(mp.y,e.getY());
            client.broadcast(start,"start", selected,"drag");
            client.broadcast(end,"end", selected,"drag");
        }
        repaint();
    }
    @Override
    public void mouseMoved(MouseEvent arg0) {
        // TODO Auto-generated method stub

    } 
    public void actionPerformed(ActionEvent e) 
    {
        if(e.getSource()==elipse)
            selected="elipse";
        if(e.getSource()==line)
            selected="line";    
        if(e.getSource()==rectangle)
            selected="rect";
        if(e.getSource()==save)
            save();
        if(e.getSource()==erase)
        {
            selected="erase";
            erase();
        }
    }
} 

class Button extends JButton
{
    String name;
    public Button(String name) 
    {
        this.name=name; 
        Dimension buttonSize = new Dimension(35,35);
        setMaximumSize(buttonSize);     
    }
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        //g2.setStroke(new BasicStroke(1.2f));
        if (name == "line")     g.drawLine(5,5,30,30);   
        if (name == "elipse") g.drawOval(5,7,25,20);
        if (name== "rect") g.drawRect(5,5,25,23);

    }
}