Sadly there is non,

There is a "Dedicated" mode in JJ2, where you minize your jj2 window and your player disappears from the game, but theres a bug in that (Levels wont change).

the main way a lot of servers are down now is using tools like Catacylism by Overlord, if your interested in hosting a server I'd recommend that.


Although with all Dedicated servers, im pretty sure this wont last..... JJ2 is just to unstable.