One thing I can think of is that RMI in an
applet is usually restricted to connecting back to the server that served the web page, not to any other server. Other than that, I'm not sure what you mean by Applet-Servlet communication.
Servlets process requests, usually HTTP requests. An RMI client needs to talk to an RMI server, not a Servlet. This server may be running in the same JVM that runs Servlets, but it would at least be in a different
thread from the Servlet runner.