Server Socket Java send several message but Client receive always the same

Question

I've a problem with Server/Client socket. The server sends several object to the client, but the client always has the first message that receive and doesn't receive the other. If I print a message in the client, it receive message, but if I print these message they are always the same. But if I print the message on server side the message are different. Can you help me? I've seen that if I send Integer all works fine. There is the problem only with the object that I must send. This is the code of the server and the client(they are linked to a GUI and a controller):

Server

    @Override
public void update(Observable o, Object arg) {

        if(o instanceof ModelChanges){
            arrayPlayersSocket = socketServerCreate.getArrayPlayerSocket();
            Iterator<ObjectOutputStream> arrayIterator = arrayPlayersSocket.iterator();
            while(arrayIterator.hasNext()){
                outputMessage = (ObjectOutputStream)arrayIterator.next();
                System.out.println(((ModelChanges)arg).getAzione());
                try {
                    outputMessage.writeObject(arg);
                    outputMessage.flush();
                    /*if(arrayPlayersSocket.indexOf(outputMessage) != controller.getTurn().getCurrentPlayer()){
                        ModelChanges modelChanges = new ModelChanges();
                        modelChanges.spegniBottoniOnLine(false, false, false);
                        outputMessage.writeObject(modelChanges);
                        outputMessage.flush();
                    }*/
                } catch (IOException e) {
                    System.out.println("IOException while the server sends an object to the client!");
                    return;
                }
            }
        }

}

Client

    @Override
public void run() {

    while(true){
        try {
            message = inputMessage.readObject();
            if(message instanceof Integer){
                socketClientCreate.setArrayIndex((Integer)message);
            }else if(message instanceof ModelChanges){
                ModelChanges modelChanges = (ModelChanges)message;
                view.getMappa().repaintView(modelChanges);
            }

        } catch (ClassNotFoundException e) {
            System.out.println("ClassNotFoundException waiting a message from the server!\n"+e.getStackTrace());
            return;
        } catch (IOException e) {

        }
    }

}