I venture a response although it is not entirely clear what you are trying to achieve.
Remote Method Invocation, RMI for short, is a mechanism in the Java world to communicate between objects/classes on potentially different hosts or Java containers. For example. the SAS Remote Services use it. It is actually a mechanism that is largely under the hood of SAS and will only require attention when things fail.
Adding ports would not likely help in any way. Adding same-numbered ports would cause conflicts and yield errors. Adding ports below 1024 would potentially cause authorization issues as these are priviliged.
Hope this helps,
- Jan.