Client/server - sending ArrayList over network

Question

Hi all
I have have written a multithreaded client/server application where multiple clients connect to the server. For each client, the server spawns a new thread to handle the connected client. When a client connects to the server, the client sends its name to the server. The server stores the name in an ArrayList and sends the whole ArrayList to all the connected clients.
It worked fine a few days ago. But now I have a problem: When I send the ArrayList to all the connected clients then only the newly connected client gets the updated ArrayList while the previously connected clients get the ArrayList that they got previously i.e. they are not updated. If instead of sending an ArrayList, I just send the name of the newly connected client to all other connected clients then it works i.e. each client gets updated with that name. It also works fine if I just send an Integer value to all the clients upon a new connection.
I know the ArrayList implements Serializable, but I dont know how it doesnt work anymore!
Plz help me with this. I have been trying all combinations, but no luck so far.
thank you
taurean

Answer 1

thank you jwentling
to make sure that we are on the same page, here is the relevant code.
This method updates the list of the peers' names on the Gui (that extends JFrame).
public void update(final ArrayList dataPacket)
          SwingUtilities.invokeLater(new Runnable()
               public void run()
                    setTitle(dataPacket.toString());
                    peerList.setListData(dataPacket.toArray());
                    peerList.updateUI();
     }This inner class continuously listens to server to get the arraylist that contains the names of the other peers/clients that are connected.
The con varibale is the Connection where I obtain input/output streams for this client.
Note: con.getInputStream() returns ObjectInputStream.
     private class Listener implements Runnable
          public void run()
               while(true)
                    ArrayList dataPacket = (ArrayList) Receiver.receiveObject(con.getInputStream());
                    if (dataPacket != null)
                         update(dataPacket);
     }Here is how the static receiveObject() metod looks like:
public static Object receiveObject(ObjectInputStream stream)
          Object obj = null;
          try
               obj = stream.readObject();
          catch(ClassNotFoundException cnfe)
               System.out.println(cnfe.getMessage());
          catch(IOException ioe)
               System.out.println(ioe.getMessage());
          return obj;
     }i think that the receiveObject() method should return the updated list (sent from server), but i get the previoulsy sent list fromt his method!!!
Has it to do something with the stream? I mean could it be that the list is still in the stream (as you pointed out) and instead of the updated list, i just get the one from the stream that i got initially?!
thank you for ur time