GZDoom multiplayer

how 2 gzdoom multiplayer:

referential material:
http://zdoom.org/wiki/Multiplayer
http://zdoom.org/wiki/Command_line_parameters
http://portforward.com/english/routers/port_forwarding/

first off: don't try to play with more than two players unless you're all on a LAN. It just won't work.

second: make sure both you and the guy you want to play with have the latest version of gzdoom
you can acquire it here: http://devbuilds.drdteam.org/gzdoom/ (the one at the top is the most recent)

third: both players need to have port 5029 forwarded on their routers. The exact steps vary by router - check the third link above for a detailed guide pertaining to your router.

fourth: make sure neither player has anything gameplay-affecting in their autoloads. Sprite/sound replacements are fine.

With G/ZDoom's multiplayer features, you can play many mods that don't currently work in Zandronum, such as Reelism, Hideous Destructor, Terrorists!, and Psychic. While lacking in gamemode options compared to Zandronum (G/ZDoom only has Cooperative and Deathmatch, just like the original game), the greater variety and quality of mods more than make up for it.

Starting a multiplayer game of G/ZDoom isn't especially difficult. If you're willing to use command line, it's a simple matter of typing "gzdoom -host <exact number of players> -file <mods go here> -iwad <doom2.wad and friends> -warp <map number - if playing something episodic such as Heretic or Doom 1, use -warp x y, where x is episode number and y is map number. For anything else, just use -warp XX, where XX is the map number.> -<gamemode - cooperative or deathmatch> +skill <0-4, ITYTD to NM>" while in your GZDoom directory. If successful, the game will not proceed beyond the startup console until all players have connected.

Joining is even easier. Just type "gzdoom -file <mods, in same load order as host> -iwad <same as host> -join <host's IP address>. If everything goes well, you'll connect and begin playing pretty much right away.

If you're afraid of a little CLI fun, you can download ZDL and just use that instead. Casual.

Troubleshooting:
>we tried to play but immediately got an "Out of sync with: X" message and the game was unplayable
One player's load order is not like the other's, you loaded different IWADs, or someone left a gameplay mod in their autoloads. Also, some mods just aren't multiplayer-compatible. You should only assume this is none of the other possible causes are present.

>we tried playing, and it worked fine for one map, but then went out of sync when entering the next map
a known bug. Both players should check to make sure that "wi_noautostartmap" is false.

>I'm typing in the correct IP and the other player is hosting but the game never starts
Both players need to have port 5029 forwarded in order to play.