Multiplayer

Multiplayer is a term used to represent a game with multiple players. This can be in a competition style, such as deathmatch, or a cooperative style of play against the game's monsters.

Technical details

ZDoom uses UDP/IP for all network play. The game state is tracked on a peer-to-peer system, unlike the csDoom derivatives or Skulltag, which are much better suited to larger-scale games because of their focus on improved networking efficiency and client-server architecture.

Multiplayer games must be started either from the command line or from a launcher of some sort. A sample set of command lines follows:

zdoom -host 2 -warp 01 -skill 4
zdoom -host 2 -deathmatch -warp 01
zdoom -join 192.168.0.1

For more information, please see Command line parameters.

• The first command line tells the computer to host two nodes (itself and one other), warp immediately to MAP01, and set the skill level to Ultra-Violence.
• The second one also hosts two, but uses the default skill level (Hurt Me Plenty), and sets the game mode to deathmatch.
• The third one joins a server hosting any kind of game, at the specified IP address, and on default port 5029.

A person joining a game does not need to specify any additional parameters aside from loading any custom WADs or DeHackEd patches that the host is using. Using custom levels and patches that are not in use by everyone in the game will cause consistency failures and the game will desynchronize.

If you want to play online, you can use a tool such as Doom Connector, Doomseeker, or IDE to find opponents and to set up a game by simply setting the settings with a mouseclick and then launch it. This system also works if you want to play over LAN, but you do need an Internet connection.

Game modes

ZDoom supports three different multiplayer game modes. Multiplayer source ports may also implement additional game modes, such as Capture The Flag or Domination.

Deathmatch

Deathmatch is a multiplayer game style pioneered by Doom in which players face off against each other, connected to a common area via a network.

• A point, called a frag, is granted to a player whenever he or she kills an opponent.
• Upon death, players restart at a random deathmatch start.
• Players spawn with all keys, and keys are never placed on the map (there is currently no clean way to circumvent this).

Team deathmatch

Team deathmatch is a variant of deathmatch where players are placed into two or more teams. Players score frags by killing members of opposing teams. Gameplay options allow to reduce or remove friendly fire damage.

Cooperative

Cooperative gameplay, often referred to as co-op or coop, is a multiplayer game mode in which human players cooperate against a given game's monsters. Cooperative play is the default game mode if the -deathmatch parameter is not specified at the command line.

Savegames

It is possible to create savegames in multiplayer (useful for cooperative gamemode). When saving, the save is written on each computer. Loading a savegame, however, is more complicated: it must be done from the command line. Both the host and each joiners must use -loadgame name_of_savefile in addition to -host or -join. It is not possible to load while the game is already in progress.

Multiplayer source ports

There are five ZDoom-based ports that have improved networking code, specialized for online multiplayer:

• csDoom is no longer being maintained. It was based on ZDoom's version 1.22 source code and had its own network code. csDoom was the first client/server multiplayer port.
• Odamex is a continuation of csDoom developed with a "back to basics" approach and the only one to be open source. It has recently started to implement support for some features of ZDoom 1.23 beta so as to compete with ZDaemon.
• Skulltag, not just a multiplayer-oriented source port, but full multiplayer mod with new weapons, bots with their own set of unique character traits, new levels designed to make use of the special features available in that port, and more. It was based on the modern ZDoom 2.x codebase.
• Zandronum is the successor of Skulltag. The additional weapons, levels and other extra content have been moved to an optional add-on pack, but it is otherwise fully compatible with Skulltag.
• ZDaemon is another continuation of csDoom by a different team and with additional features, including some features from ZDoom 1.23 betas, such as slopes.