Re: RMI & connection refused

"Matt Humphrey" <>
Mon, 3 Aug 2009 14:39:00 -0400
"Nigel Wade" <> wrote in message

Matt Humphrey wrote:

If your server
happens to create additional remote objects, each will get its own port.
don't have to know or handle the port number, but a firewall will block
access. Similarly, remote objects instantiated on the client (RMI
callbacks) will open a server socket on the client and the server's
proxy will attempt to connect to that port. Again, you don't have to
any of the port numbers for this to work, I'd rather not open ports on

If you don't use the rmiregistry, and you don't know or handle the port
how does the client determine the port number on which the server is

Sorry, I was unclear. Clients need the port number to find the top-level
server object. Remote objects instantiated within the server get dynamic
port numbers, but the client doesn't need to know them (see below). For
other instantiated remote objects and RMI callback objects, the port numbers
are managed automatically. The code below shows the basic structure (but is
otherwise uncompiled, untested, unstructured, etc.) In using Eclipse w/ Java
1.6 I don't need to invoke rmic--stubs and skeletons are handled
automatically. Just make sure all the class referenced by the client are
actually available to it. In the example below, that would be Server and
Session. ServerImpl and SessionImpl are not needed by the client.

To setup direct server (note that rmic is not needed under more recent Java
1.5?)--uncompiled, untested, structured only as an example

// Declare your server interface
public interface Server extends Remote {
  void doThis (String p0) throws RemoteException;

  // Example of dynamic remote object
  Session createSession (String username, String pw) throws RemoteException;
public interface Session extends Remote {
  void doThat () throws RemoteException;

// Declare your session object--totally optional
public class SessionImpl extends UnicastRemoteObject implements Session {
  public void doThat () throws RemoteException { // whatever

// Declare your server
public class ServerImpl extends UnicastRemoteObject implements Server {
  public void doThis (String p0) throws RemoteException {
    // Do whatever here
  public Session createSession (String u, String pw) throws RemoteException
    SessionImpl newSession = new SessionImpl ();
    // whatever session needs.
    // Once returned, it will appear to the client as a proxy object, not
    // actual SessionImpl object, hence the client always sees it as Session
   return newSession;

  public static final void main (String [] args) {
    LocateRegistry.createRegistry(5005 /* your port number */);
    ServerImpl actualServer = new ServerImpl ();
    Naming.rebind("YourServerName", actualServer );
    // Wait until directed to exit

public class ClientApp {
  public static final void main (String [] args) {
    Server remoteServer = Naming.lookup ("//<host>:5005/YourServerName");
    Session newSession = remoteServer.createSession ("my", "pw");

Matt Humphrey

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