title: RMI notification from server to client on update
body: <p>I'm writing a dummy shipping app. The client sends a product, and the server keeps all products that are sent. </p>
  
  <p>Now the server - because it is just virtual - updates the state of the product every minute (SEND -> ACCEPTED -> SHIPPED -> RECEIVED), now i want the server to update the corresponding client when it has updated the state.</p>
  
  <p>Most RMI information I fiend only talks about client -> server.. But i need my server to call my client for this one..</p>
  
  <p>Hope you guys can help !</p>