Can a RMI Server trap an exit event of its client ?

Question

Hi all,
Can a RMI Server trap an exit event of its client ??
For example
If I close the client using Ctrl-C, can the Server known what one of its client is closed ??

Answer 1

You could consider allocating a new remote object per client via some login object. In my book I called this the 'remote session' pattern. That way each client can have its own server-side context, i.e. like an EJB session bean, which can have its own advantages. In fact if you're interested in when a specific client disappears, you must already have some client context so this is a clean solution to that as well.
Then the session object can use the Unreferenced technique to know when the client has gone away unexpectedly, albeit with a 10 minute delay. This can be tuned via the java.rmi.dgc.leaseValue setting at the server. This works because each session object only has one client.
If you can't do this and you can't control the client code, I'm not aware of any other solution under RMI.
Except that as a last resort you could do something really fancy with custom socket factories at both ends that both implement a special ping protocol I suppose, but this is getting pretty hairy and you'd need to understand the RMI wire protocol to make it work.