Socket I/O question

Is there a standard pattern to follow for developing network applications that do request-response type conversations?
I've built something but it's kludgy and relies upon instanceOf in delivering the response to the object that requested it. The remote system is non-java based.

You're passing an object back and forth but one side isn't Java-based? I'm not sure I understand.
There's pretty much two general ways to do this sort of thing: use object serialization and define your own protocol for the request-response communication, or use a framework like RMI or CORBA to manage some of the lower-level details of that protocol.

Actually I was thinking along other lines. I can only communicate with the remote host at the socket api level. I implement a ServerSocket class and need to maintain stateful info about the sessions which operate asynchronously. This is probably a common thing to do, and so thought there just might be an oop design pattern suitable that I could use.