如何在RMI中的服务器上正确注册客户端？

Question

I'm currently working on a small project that manages attendance for a summer program that I'm helping run. The RMI server is run from the office and has a specific port set for it by using the following code:

Registry registry = LocateRegistry.createRegistry(4051);
RemoteManager stub = (RemoteManager) UnicastRemoteObject.exportObject(theServer, 4051);
registry.rebind(SERVER_NAME, stub);

where theServer is a reference to the object that will serve as the system's server and SERVER_NAME is simply a static String used to represent the server. As is shown the registry binds the server to port 4051 so that clients can query for it. Now I'm working on cross-communication between the server and multiple client instances (12 teachers running the same client program) and currently it is set such that the clients send stubs of themselves to the server for client registration.

public void registerClient(INTERFACE_Client teach) throws RemoteException {
.
.
.
}

where INTERFACE_Client extends the Remote interface and the client is sent down by calling:

server.registerClient((INTERFACE_Client) UnicastRemoteObject.exportObject(this, 4052));

where I just chose port 4052 because I didn't know what I was doing. I also didn't bind the stub to a registry. Is a good way to do it? Because I've hardcoded the client port, all 12 teachers will be exporting the object using port 4052 (at least that's how I see it) from their respective client instances. Should the ports be randomized? Should I not include a port (there's a method that doesn't require that as well)? Any helpful hints would be greatly appreciated.

As a disclaimer, I do need a reference to the client in the server so that people in the office can send messages to the teachers. (Server -> Client communication). The client already has the reference to the server because it can look it up on the registry.
Any suggestion?

Answer 1

I just chose port 4052 because I didn't know what I was doing.

That's OK, as long as port 4052 is open in both directions in both intermediate firewalls, if there are any firewalls. There's no real reason why you can't use the RMI Registry port 1099 for this, at both ends: it's already reserved by IANA, unless the hosts already contain some other RMI application.

I also didn't bind the stub to a registry. Is a good way to do it?

That's OK. You don't need a Registry at the client. All you need is your existing registration API.

Because I've hardcoded the client port, all 12 teachers will be exporting the object using port 4052 (at least that's how I see it) from their respective client instances.

That's OK as long as the 'client instances' are all separate TCP hosts.

Should the ports be randomized?

Not unless you have > 1 client per TCP host.

Should I not include a port (there's a method that doesn't require that as well)?

No.

Any helpful hints would be greatly appreciated.

Your clients must implement a remote interface and be exported and then registered with the server via your existing API. You're doing well. As long as there are no firewalls, or they are all under your control, you will be OK.