This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
You cannot send a remote object reference over the wire and call it. That's not how it works. There is a Remote interface. Your remote interface extends that. Your remote class impelements the interface. You must then deploy your remote interface to an RMI server to indicate where the actual remote object lives. The client (e.g., socket B) does a lookup in the registry and gets an instance of the remote proxy that implements the remote interface. The proxy calls are marshalled over the wire to the actual object on the remote server.