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.

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


 * A point, called a frag, is granted to a player whenever he or she kills an opponent.
 * Frags are deducted when a player commits suicide, or dies in a crusher or damaging floor.
 * 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).
 * When the level ends, the intermission screen gives each player's frag count. (Note that many PWADs specialized for deathmatch play do not contain exits.)

A deathmatch game may use either normal or altdeath rules (see Command line arguments).

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 deathmatch mode is not explicitly specified at the command line.

Because the players are not adversaries under coop rules, they are visible on one another's automaps, and each can even "look through the eyes" of his companions (though their status bars cannot be viewed).

In vanilla Doom, certain game interface features behave differently in multiplayer mode. For example, any player can pause or unpause the game at any time, and using the "save" command causes the game to be saved in the same slot on each machine. Also, when accessing the in-game menus (options, sound, save, load, etc) the game does not pause.

During the design of a map, objects can be flagged to appear only in multiplayer games. In stock maps, this is normally used to insert extra weapons and powerups, which provide a more balanced supply of armaments in cooperative play and more interesting "arms races" during deathmatch play. Beginning with Doom II, most stock levels also contain extra monsters, usually boss monsters; these provide more fearsome opposition for cooperative play and act as booby traps in deathmatch play. (Because of the extra monsters, some speedrunners enjoy the challenge of completing max runs in multiplayer mode, using DOS utility programs to create a fake "second player" who neither moves nor attacks.)

Chocolate Doom
This is a source port which attempts to mimic almost all of vanilla Doom's original behaviour. This port remains compatible with Doom, but not on a network level, since TCP/IP and IPX are incompatible.

Chocolate Doom's network engine is still under development, but it is already quite stable.

A program such as Doomwire which is dedicated to using Chocolate Doom can be used to play peer-to-peer on the Internet or on a LAN with other players.

ZDoom-based source ports
ZDoom uses a TCP/IP architecture for all network play; the game state is tracked on a peer-to-peer system. Players in search of co-op allies or deathmatch opponents can use Doom Connector or Internet Doom Explorer to set up a game. This system also works with LANs, but an Internet connection is also required.

Three further ports have improved on ZDoom's networking code by incorporating client/server network architecture:


 * csDoom, based on ZDoom version 1.22, was the first client/server multiplayer port.
 * ZDaemon is derived from csDoom (with a new maintainer). The current version of ZDaemon incorporates code from newer versions of ZDoom, and therefore supports many of ZDoom's newer map-making features.
 * Skulltag features new weapons, customizable AI "bots", entirely new variants of multiplayer rules, and sample levels designed around ZDoom's non-vanilla features.

These ports are capable of running large-scale multiplayer games more smoothly, as they were written specifically with network play in mind.