Board Thread:Bug Reports/@comment-27130828-20151226020138/@comment-27723099-20151226052254

Rocket Engineer wrote: Completely unhelpful, but I think an "internal server" is something forge does. It turns your single player worlds into a server so that mods don't have to work for "vanilla single player" and servers. Don't quote me on this, I'm probably wrong. That is a good explanation. Minecraft always uses a server-client model for the reason to make singleplayer and multiplayer the same.