Notes

So we start from this very simple set up:

class Setup {
  public static void main(String[] args) {

    Server server = new Server(); 

    Client a = new Client(); 
    a.registerWith(server); 

    Client b = new Client(); 
    b.registerWith(server); 

    Client c = new Client(); 
    c.registerWith(server); 

  } 
}

Three clients and a server: clients register with the server.