Notes

Here are two objects; the object on the left could easily remotely access the object on the right (because of the microphone, headphones).

Still, the object on the left does not have to be far away to communicate (the way it does) with the object on the right.

This is what RMI provides: a pair of headphones, that the objects can forget about, to yell at each other when they need to, and from any distance.

It is important to understand that having the headphones on is virtually transparent to objects, as in the picture above.

So you can start the programs locally (in the same address space) or separately (on the same machine, or on different machines).

By contrast, using sockets to connect remotely requires learning a specific API, one that may have nothing to do with your problem.