Very horrible applet problem

Hi,

I'm writing a server-client program that communicates over TCP. When
a user connects, a new thread is created (yes, this is very bad, but
I'm learning).

The problem I'm having is when the user disconnects. If the user is
running the client program as an applet in a web browser, the server
does not remove their connection from the hashtable of clients when
they disconnect

Here is the code for the ServerThread class:

package server;

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

public class ServerThread extends Thread
{
    // The main server thread
    private Server server;
    // The Socket that the client is connected to
    private Socket socket;
    String message;
    // Constructor.
    public ServerThread( Server server, Socket socket ) {
        this.server = server;
        this.socket = socket;
        start();
    }
    public void run() {
        try {
            // Create a BufferedReader for communication
            DataInputStream din = new DataInputStream(socket.getInputStream());
            // Create an output stream for commands like ping
            DataOutputStream dout = new
DataOutputStream( socket.getOutputStream() );
            // Over and over, forever ...
            while (true) {
                // ... read the next message ...
                message = din.readUTF();

                System.out.println("Client "+socket+" sending command");

                if (message != null)
                {
                    // The input from the client is handled here, which results in a
message being sent back, and/or a message being sent to other clients
                }

            }
        } catch( EOFException ie ) {
        } catch( IOException ie ) {
            ie.printStackTrace();
        } finally {
            System.out.println("Client disconnected");
            // The client has disconnected, so have the server remove them from
the hashtable with this method
            server.removeConnection( socket );
        }
    }
}

Is this something to do with Java Applets? I have tested this with
Firefox, and with the applet viewer, and the applet viewer closed the
connection fine.

Thanks in advance,

--James.