RMI Questions

[Shannon Sims]

Good evening,
I've searched all the posts regarding RMI in this forum and in the Java Intermediate forum and have not found any that address my issues. Can someone please help me?

I'm using Eclipse SDK 3.1.0 to run a small RMI program (if I can get this to work, I can get back to working on my B&S project). If I don't manually start the RMI server via the command line, I get a ConnectionException even though LocateRegistry.createRegistry(1099) is being invoked inside the server code. I understood that by invoking createRegistry(), it would start the RMI server, is this correct?

If I run the RMI server before running the program I then get a NotBoundException invoking Naming.lookup(). I started the RMI server at the root level (E:\ drive). Do I need to start the RMI server in the directory where the stub and skeleton is or where the class files are? My stub and skeleton are in a folder together, a subdirectory where all my class and java files are.

Perhaps the NotBoundException is due to my lack of understanding of what exactly is the parameter for the Naming.lookup()? It's the directory to what, the skeleton directory?

While searching other RMI posts, one post brought on a question about where the stub and skeleton should reside. If I have a client and server jar file, shouldn't the stub reside in the client jar file and the skeleton in the server jar file?

Thanks for you time and feedback!

[Alex Belisle Turcot]

Hi,

Yes LocateRegistry.createRegistry(1099) will start the "rmiregistry.exe".

After that, you need to bind the server object to it:

Naming.rebind("//localhost: port/SomeText", (ServerIF)new ServerObject());
 
//I added a extra space right before the word "port", to avoid create an emoticon. 
//Just remove it.
//port = the port you started the rmiregistry.exe on.

For this code to work, you must create the stubs for the ServerObject.

Then, on the client's side, you need to lookup for the "SomeText" to get the object:

ServerIF serverIF = (ServerIF) Naming.lookup("//IP: port/SomeText");
 
//I added a extra space right before the word "port"... 
//port = the port you started the rmiregistry.exe on.
//IP = ip of the machine you started the rmiregistry.exe on.

Here, IP could be another machine's ip, or "localhost" if the client and server are on the same machine. It's where rmiregistry.exe is running, which is always on the same machine as the server (rmiregistry limitation: meaning a server cannot bind itself to a remote rmiregistry.exe).

The client needs to have access to the stubs too.

I believe in current java version, the skeleton is not used (managed behind the scene). not sure.

NotBOundException is thrown (on the client's side) because your server object was not previously bound successfully before you tried to lookup for it.

Hope this helps, any guru please feel free to correct me and help him some more.

Regards,
Alex
[ February 04, 2006: Message edited by: Alex Turcot ]

[Kevin Conaway]

Shannon,

I use the LocateRegistry classes in my code and bypass Naming all together

Server:

Registry registry = LocateRegistry.createRegistry(1099);
registry.bind("MyServer", new MyServer());

Client:

Registry registry = LocateRegistry.getRegistry(1099);
MyServer server = (MyServer) registry.lookup("MyServer");

Good luck,

Kevin
[ February 05, 2006: Message edited by: Kevin Conaway ]

[Shannon Sims]

Hi Alex,
Thank you for your reply! This is a wonderful place where others are so kind to share their knowledge.

I guess a good nights rest is all I needed...the server side code needed to be executed before running the client code...I was only running the client code, which explains why I was getting a ConnectException.

Thanks Alex!

[Shannon Sims]

Hi Kevin,
Thanks for your reply. Very interesting, most of the posts I've seen use the Naming instead of the Registry? It seems logical to use the Registry, however most of the posts are using the Naming, instead? It is more efficient to use the Registry?

[Kevin Conaway]

Shannon,

I believe the Naming class is just a shortcut for the LocateRegistry methods. Most people use the Naming methods because most tutorials and guides use them. Naming apparently just parses the url that it accepts and passes it along to LocateRegistry.

I don't believe there is an inherent advantage to using either of these. For code consistency however, if you are using LocateRegistry, you should stick with that.

Kevin

[Shannon Sims]

Hi Kevin,
Thanks for the explanation. Either way, I guess I'm safe to utilize the Naming or Registry APIs.

[Bob Nedwor]

Kevin!
You Rock! This info has helped me tremendously!!! Thanks a bunch!

--Bob (the RMI wanna-be)

[Yupp Cook]

Even better it seems to me

using registry.rebind(...) instead of registry.bind(...)
avoid the AlreadyBoundException

Regards
Y