Re: client server - client problem

From:

solomon13000@gmail.com

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 08 Oct 2007 08:24:08 -0700

Message-ID:

<1191857048.217703.236950@d55g2000hsg.googlegroups.com>

On Oct 8, 8:41 pm, Gordon Beaton <n....@for.email> wrote:

On Mon, 08 Oct 2007 04:43:50 -0700, solomon13...@gmail.com wrote:

The code above is a client server application. What the client does
is that it sends the coordinates of what is drawn on a canvas to the
server. The server will receive this coordinates and retransmit it
to all the clients connected to the server and display it on the
canvas. The client server concept work well, however after
implementing this concept, I cant see what I have drawn on the
canvas, but it does send the coordinates to the server.

At first glance, I see a number of problems with your networking code:

- the server is written to accept only one client at a time
- only one client on "localhost" can bind a ServerSocket to port 9000
- you don't need to use two sockets between each client and the
server, the socket already provides a channel in each direction.
- you should be able to keep the connections open, there is no need to
reconnect (twice!) for every message.

Also, it appears that your init() method will never finish.

I suggest you read the Java networking tutorial, and post shorter
examples. See if you can make this work as an application, before
making an applet.

/gordon

--

I did the changes as in to use a single connection:

GandhiServer2.java
------------------

import java.net.*;
import java.util.*;
import java.io.*;
public class GandhiServer2
{
    ServerSocket ss;
    Socket cs;
    Vector ht;
    ObjectInputStream ois;

    Socket skt;
    ObjectOutputStream oos;

    public GandhiServer2()
    {
        try
        {
            ss = new ServerSocket(9000);
            cs = ss.accept();

            while(true)
            {
             ois = new ObjectInputStream(cs.getInputStream());
             ht = (Vector)ois.readObject();

             if(!ht.isEmpty())
             {
             try
         {
             oos = new
ObjectOutputStream(cs.getOutputStream());
             oos.writeObject(ht);
             oos.close();
         }
         catch (Exception e)
         {
              e.printStackTrace();
         }
             }

             System.out.println(ht);

             ois.close();
             ht.clear();
             cs.close();
             cs = ss.accept();
            }

        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    public static void main(String[] args)
    {
        new GandhiServer2();
    }
}

WhiteBoardApplet.java
---------------------

I included a portion of the code as the code is to long.

public void mouseReleased(MouseEvent e)
{
    isButtonPressed=false;

    try
    {
        skt = new Socket("localhost", 9000);

        oos = new ObjectOutputStream(skt.getOutputStream());
        oos.writeObject(ht);

        ois2 = new ObjectInputStream(skt.getInputStream());
        ht2 = (Vector)ois2.readObject();

        System.out.println(ht2);

        oos.close();
        ht.clear();

        ois2.close();
        ht2.clear();
    }
    catch (Exception x)
    {
        x.printStackTrace();
    }

    message.setText("Mouse released.");
    }

    public void mouseEntered(MouseEvent e){
    }

    public void mouseExited(MouseEvent e){
    }

    //*****MouseMotionListener methods

    public void mouseDragged(MouseEvent e){
    if(isButtonPressed==true)
    {
        pre_x=e.getX()+scrollbarH_value;
        pre_y=e.getY()+scrollbarV_value;
        isButtonPressed=false;
    }
    x=e.getX()+scrollbarH_value;
    y=e.getY()+scrollbarV_value;
    offscreenImageG.drawLine(pre_x, pre_y, x, y);
    drawLines(pre_x + ":" + pre_y + ":" + x + ":" + y);
    pre_x=x;
    pre_y=y;
    repaint();
    e.consume();
    message.setText(pre_x + ":" + pre_y + ":" + x + ":" + y);
} //end mouseDragged

public void drawLines(String m)
{
   ht.add(m);
}

Now I open two whiteboards. When I draw one whiteboard-1, the
coordinates are send to the server. Now the server receives the
coordinates and send's the coordinate back to whiteboard-1. The
problem I am facing is it does not return the coordinate to
whiteboard-2 as well. How do I solve the problem?