I'm baffled more off I'm discussing msging and networking in general and its foundation, while you seem to be discussing more higher level abstract implementations on the different game engines, but the foundations has not changed a lot used to be UDP and then when over to TCP and now we are back in UDP with some Tcp functionality but don't quoate me i'm not keeping up to date xD. But anyhow just knowing the basic concepts of how a server send message to another server on a network would tell you that if you build something that can do it over the internet, doing it for offline local is much simpler.

Perhaps it is my upbringing with watching kid friendly short movies explaining this that make it seem obvious to me.