Reelism can be played in online multiplayer with your friends for a co-operative you-and-your-pals-against-the-slathering-canine-horde experience you won't forget in a hurry, no matter how much therapy you hurl at it. However, there's a few things you'll need to keep in mind before you go all crazy and start plotting out 32-player competitive contests at Dreamhack and whatnot.
Since Zandronum lags behind GZDoom feature-wise, we can't guarantee that this will work. You may need to use an unstable pre-alpha build. We recommend using GZDoom and doing the command-line shuffle (or more likely, the find-a-launcher shuffle) to get everyone in-game. Sorry!
Frankly, you should just read this.
MAKE SURE EVERYBODY IS USING THE SAME VERSION OF GZDOOM AND REELISM! MAKE SURE EVERYONE HAS THE SAME ADD-ON WADS LOADED IN THE SAME ORDER! One slight difference and the game will go out of sync really quickly, requiring the game to restart.
Reelism only supports co-op play. Obviously, monsters must be enabled.
Now, this one's important. Set your starting map to LOBBY. Do this by having the host add "+map lobby" to his/her commandline. This will provide you with a convenient map select for multiplayer. Decide on a map to play then jump through the gate! Sorted!
So as to allow for maximum carnage to ensure, you can freely respawn in Reelism. However, dying will cost you 2000 points. Once the boss has been killed, your team's combined score will be displayed and you'll be sent back to the Lobby to try another map.