I am using

Java platform:jdk 1.4.1
Windows platform: Windows 98se

Problem:I am making one application in which i need to display images
when i get
it from socket.I had used one JScrollPane over JPanel with
scrollbars.But when i get the image i stored it into an Image object.

such as in my main program
screen =  Toolkit.getDefaultToolkit().getImage ( "screen.jpg" );

//Draw picture first time it works fine...
paintPicture(screen);

paintPicture(Image image)
    {picpnl = new JPanel();
    picpnl.setLayout(new BorderLayout());
       image = Toolkit.getDefaultToolkit(  ).getImage(image);

//Is picpnl is unable to display image second time

     picpnl.add(new JScrollPane(new
ImageComponent(image)),BorderLayout.CENTER);
       c.add( picpnl, BorderLayout.CENTER );
       picpnl.setVisible(true);

       ---
       ---
from my refresh code:
      if(image!=null)
        image.flush();
      Runtime rt = Runtime.getRuntime();
      rt.runFinalization();
      rt.gc();
      image = null;

//is this 2nd time image not properly stored in variable image

      image = Toolkit.getDefaultToolkit().createImage( b ,0, b.length
);
      paintPicture(image);

//go to paintPicture second time doesn't work

class ImageComponent extends JComponent {
 Image image;
 Dimension size;

 public ImageComponent(Image image) {
   this.image = image;
   MediaTracker mt = new MediaTracker(this);
   mt.addImage(image, 0);
   try {
     mt.waitForAll(  );
   }
   catch (InterruptedException e) {
     // error ...
   };

   size = new Dimension (image.getWidth(null),
                         image.getHeight(null));
   setSize(size);}
  public void paint(Graphics g) {

    g.drawImage(image, 0, 0, this);
 }

 public Dimension getPreferredSize(  ) {
   return size;
 }
}

The above code works fine for (the first time).But when i try to
display a different socket image (the second time) it doesn't work.

I didn't know what the problem is...
---whether the previous image didn't get erased from RAM or
---the OS is not aware of the current changed image in variable (image)
or the
---JScrollPane is unable to redraw it second time.

How can i display one changed image from the socket onto the
JScrollPane? (the second time).

Also i want to know if we are using one file with the name "screen.jpg"
and at runtime if i changed that file with another file with the same
name. How can i display that changed file?Is it possible in Java or
not.(Is it the limitation of Java).

I totally get frustated by reading all forums but i didn't get the
answer.Please reply me soon with the complete code?

The complete source code for the problem:
(SERVER):
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.text.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class Remote extends JFrame
{
 private JPanel btnpnl,picpnl;
 private JButton button[];
 private UIManager.LookAndFeelInfo looks[];
 private static int change = 1;
 private JLabel label1;
 private Icon icon[];
 private String names[] = { "looks","connect","control", "refresh",
"auto",    "commands" };
 private String iconnames[] = {
"gifs/look.gif","gifs/connect.gif","gifs/control.gif","gifs/refresh.gif","gifs/auto.gif","gifs/command.gif"
};
 private String looknames[] = { "Motif", "Windows", "Metal" };
 private int port=5000;
 private ScrollablePicture picture=null;
 private ServerSocket server;
 private Socket client;
 private ObjectInputStream ins = null;
 private ObjectOutputStream ous = null;
 private File file;
 private String fileName;
 private boolean autocontrol=true;
 private Image image=null;
 private Container c;

    public remote()
    {
        super( "Remote Desktop" );
               c = getContentPane();
        c.setLayout( new BorderLayout() );
       //String file = "screen.jpg";
               looks = UIManager.getInstalledLookAndFeels();

        btnpnl = new JPanel();
        btnpnl.setLayout( new FlowLayout() );

        button = new JButton[names.length];
        icon = new ImageIcon[iconnames.length];
        Buttonhandler handler = new Buttonhandler();

        for( int i=0; i<names.length; ++i )
        {
                  icon[i] = new ImageIcon( iconnames[i] );
            button[i] = new JButton( names[i], icon[i] );
            button[i].addActionListener(handler);

                        btnpnl.add(button[i]);
                }

        c.add( btnpnl, BorderLayout.NORTH );

        //Adding Label1

        label1 = new JLabel("LABEL1");
        c.add( label1, BorderLayout.SOUTH );

           picpnl = new JPanel();
       picpnl.setLayout(new BorderLayout());
        //image = Toolkit.getDefaultToolkit(  ).getImage(file);
      // paintPicture(image);
        c.add( picpnl, BorderLayout.CENTER );
        //setResizable(false);
        setSize( 808, 640 );
        show();

}

public void paintPicture(Image image)
   {
       picpnl.add(new JScrollPane(new
ImageComponent(image)),BorderLayout.CENTER);
       picpnl.setVisible(true);
   }

public class Buttonhandler implements ActionListener
    {
        public void actionPerformed( ActionEvent e )
        {

              try{
            if( e.getActionCommand() == "looks" )
        {
              try
              {
            label1.setText( Integer.toString( change ) );

        UIManager.setLookAndFeel( looks[change++].getClassName() );

SwingUtilities.updateComponentTreeUI(remote.this);

             if(change==3)
                 change=0;

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

            if( e.getActionCommand() == "connect" )
            {
                label1.setText( "connect" );
               runServer();
              }

            if( e.getActionCommand() == "refresh" )
                      {
                label1.setText( "refresh" );
                ous.writeObject("refresh");
                ous.flush();
                recieveFile();

            }

            if( e.getActionCommand() == "auto" )
            {
                label1.setText( "auto" );
                ous.writeObject("auto");
                button[4].setText("stop");
                ous.flush();
                setButton(false,false,false,false,true,false);
               auto();
            }

            if( e.getActionCommand() == "stop" )
            {
                ous.writeObject("stop");
                ous.flush();
                button[4].setText("auto");
                setButton(true,true,true,true,true,true);
               autocontrol=false;
            }

        }
        catch(Exception ef)
        {
            ef.getMessage();
        }

     }
    }

    public void auto()
       {
        while(autocontrol)
        {
          recieveFile();
       }
    }

    public void setButton( boolean b1, boolean b2, boolean b3, boolean b4,
       boolean b5, boolean b6)
    {
        button[0].setEnabled(b1);
        button[1].setEnabled(b2);
        button[2].setEnabled(b3);
        button[3].setEnabled(b4);
        button[4].setEnabled(b5);
        button[5].setEnabled(b6);
    }

    public void recieveFile()
    {
       int flag = 0;

        try{
            while(flag<=2){
            Object recieved = ins.readObject();
            System.out.println("from client:" + recieved);

           switch (flag) {
                       case 0:

                           if (recieved.equals("sot")) {
                           System.out.println("sot recieved");
                            flag++;
                       }
                       break;

            case 1:
                           fileName = (String) recieved;
                           file = new File(fileName);
                        System.out.println("fileName                         received");

                        flag++;

                       break;

            case 2:

                 if (file.exists())
                {
                 file.delete();
                }
                    byte[] b = (byte[])recieved;

                FileOutputStream ff = new FileOutputStream(fileName);

                              ff.write(b);
                              flag = 3;
                              if(image!=null)
                    image.flush();
                                                              Runtime rt = Runtime.getRuntime();
                  rt.runFinalization();
                  rt.gc();

                  image = null;
        Image = Toolkit.getDefaultToolkit().createImage( b ,0, b.length );

                paintPicture(image);

                       break;
                   }

            }

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

    }

class ImageComponent extends JComponent {
 Image image;
 Dimension size;

 public ImageComponent(Image image) {
   this.image = image;
   MediaTracker mt = new MediaTracker(this);
   mt.addImage(image, 0);
   try {
     mt.waitForAll(  );
   }
   catch (InterruptedException e) {
     // error ...
   };

   size = new Dimension (image.getWidth(null),
                         image.getHeight(null));
   setSize(size);}
  public void paint(Graphics g) {

    g.drawImage(image, 0, 0, this);
 }

 public Dimension getPreferredSize(  ) {
   return size;
 }

 }

    public void runServer()
    {
       try{
            server = new ServerSocket(port);

            client = server.accept();

JOptionPane.showMessageDialog(null,"Connected");
            System.out.println("connection received from" +
  client.getInetAddress().getHostName());

            ous = new ObjectOutputStream( client.getOutputStream() );
                       ous.flush();
            ins = new ObjectInputStream( client.getInputStream() );
            System.out.println("get i/o streams");
        }
        catch(Exception e)
       {
            e.printStackTrace();
        }

    }

    public static void main(String[] args)
    {
      remote app = new remote();
      app.addWindowListener(
          new WindowAdapter(){
                public void windowClosing( WindowEvent e )
               {
                    System.exit( 0 );
                }
          }
        );

    }

}
CLIENT code:
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.image.*;
import javax.imageio.*;

public class Client extends JFrame
{
  private JLabel label1;
  private JButton button1;
  private Socket server;
  private ObjectInputStream ins=null;
  private ObjectOutputStream ous=null;
  private File file;
  private boolean autocontrol=true;

  public Client()
    {
      super("Client");

      Container c = getContentPane();

      ButtonHandler handler = new ButtonHandler();
      c.setLayout( new FlowLayout() );

      label1 = new JLabel("");
      button1 = new JButton("connect");

      c.add(label1);
      c.add(button1);
      button1.addActionListener(handler);
      setSize(300,300);

      show();
    }

class ButtonHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e)
    {
       if(e.getActionCommand()=="connect")
       {
            runClient();
        }
    }
}

public void runClient()
{

    try{
        server = new Socket(InetAddress.getByName("127.0.0.1"),5000);
      System.out.println("connected to" +
server.getInetAddress().getHostName());

        ous = new ObjectOutputStream(server.getOutputStream());
           ous.flush();
        ins = new ObjectInputStream(server.getInputStream());

        System.out.println("get i/o streams");

            file = new File("screen.jpg");

        listencommands();
    }catch(Exception e)
    {
        e.getMessage();
    }
}
public void listencommands()
{
    try
        {

        while(true){
        Object message = ins.readObject();

       if(message.equals("refresh"))
         {
             screenshot();
             sendFile(file);
         }

       if(message.equals("auto"))
         {
             autocontrol=true;
             while(autocontrol)
             {
                 screenshot();
                 sendFile(file);
             }
         }

        if(message.equals("stop"))
        {
            autocontrol = false;
        }

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

}

public void sendFile( File file ) throws IOException
    {

    try{

        System.out.println("Ready to send file");
        ous.writeObject("sot");
               ous.flush();
               System.out.println("sot send");

        ous.writeObject("screen.jpg");

        ous.flush();
               System.out.println("fileName send");

        FileInputStream f = new FileInputStream (file);
               System.out.println("fileinputstream received");
        int size = f.available();
               byte array[] = new byte[size];
               f.read(array,0,size);
        System.out.println("Declared array");
                //ous.write(size);
                //ous.flush();

        ous.writeObject(array);
               ous.flush();

        System.out.println("image send");

        }
        catch (Exception e)
        {
            System.out.println(e.getMessage());
        }

    }
public void screenshot()
{
try
{
    //Get the screen size
   Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Rectangle rectangle = new Rectangle(0, 0, screenSize.width,
screenSize.height);
       Robot robot = new Robot();
    BufferedImage image = robot.createScreenCapture(rectangle);
    File file;

       //Save the screenshot as a png

    file = new File("screen.jpg");

    ImageIO.write(image, "jpg", file);
}
catch (Exception e)
{
    System.out.println(e.getMessage());
}
}

public static void main( String args[] )
    {
        Client app = new Client();

       app.addWindowListener(
          new WindowAdapter(){
                public void windowClosing( WindowEvent e )
               {
                    System.exit( 0 );
                }
          }
        );

     

    }
}

Good advice Roedy, the thread(s) has been a little confusing.
It must have been some work for ajay to keep them all
relatively up to date as well!