Server plugins

The Source engine comes with a built in 3rd party plugin API similar to the API provided by MetaMod under the HL1 engine. This document provides a brief description of the interfaces provided and how to best use them.

Compiling the Sample

The SDK contains a sample plugin that exercises the various capabilities available in a plugin. You can find the sample in src/utils/serverplugin_sample. Under Windows load the serverplugin_empty.vcproj project, under linux you can type:

make plugin

from the linux_sdk directory.

Running a Plugin

The engine will load plugins based upon specially formatted key value files put in the <mod dir>/addons/ folder (you may have to create this directory, a default server install doesn't come with one). To load your plugin place a file in this folder with the extension vdf and with the following format:

"Plugin"
{
        "file"  "serverplugin_empty"
}

The "file" parameter should point to the file to load. In this example the binary created after you compiled the code should be copied to the bin/ folder of the server install. The file extension (.dll for Windows) is added automatically to the filename when it is loaded. The file name should be relative to the base bin/ folder on the server (i.e you would use ../cstrike/addons/serverplugin_empty to specify a file in the cstrike addons folder).

The IServerPlugin interface

Plugins work by exposing an IServerPluginCallbacks interface to the engine. The engine calls back into this interface when various events happen. The definition of this interface can be found in public/engine/iserverplugin.h. The PLUGIN_RESULT return type of some of the functions allows the plugin to control whether this call is passed onto the underlying mod or not, see the header file for details.

IServerPluginCallbacks explained

Load	This function is called when the plugin is loaded by the engine. This can happen either on initialization or when being re-loaded after being unloaded. The two parameters provide the interface factories that the plugin needs to operate.
UnLoad	Called when a plugin is unloaded, use this to disable any asynchronous tasks and remove any callbacks you have registered with the engine (for example a game events listener).
Pause	Called when the operation of the plugin is paused (i.e it will stop receiving callbacks but should not be unloaded).
UnPause	Called when a plugin is brought out of the paused state. You should re-enable any asynchronous events your plugin uses in this call
GetPluginDescription	This function should return a friendly string describing your plugin. Typically this would be its name and the author.
LevelInit	Called on level (map) startup, it is the first function called as a server enters a new level.
ServerActivate	This is called when the server successfully enters a new level, this will happen after the LevelInit call. This call provides pointers to the list of edicts created on the server and the maxplayer count of the server.
GameFrame	Called once per server frame (typically 60 times a second). Server performance is very sensitive to the execution time of this function so keep anything you do in this function to a minimum.
LevelShutdown	Called when a server is changing to a new level or is being shutdown. Remove any map specific allocations in this call. This can be called multiple times during a map change.
ClientConnect	Called when a client initially connects to a server. Set bAllowConnect to false to stop this user from connecting.
ClientPutInServer	Called when a client spawns into a server. This is called before the server spawn function.
ClientActive	Called after a client is fully spawned and configured by the Mod. Use this call to change any player specific settings.
ClientDisconnect	Called when a client disconnects from the server.
SetCommandClient	Called by the ConVar code to let you keep track of which client is entering a ConCommand. Use this index in ConCommands if you want to see who is running the command. As ConVar commands don't have an edict associated with them when they run you can use this index to look up the entity that is running the command.
ClientSettingsChanged	Called when player specific cvars about a player change (for example the users name). Use this function to control what operations a user is allowed to perform to their settings (for example limiting usernames).
ClientCommand	Called when a remote client enters a command into the console. This should be used to provide commands to clients (and ConCommand used to implement server side only commands).
NetworkIDValidated	Called when the server retrieves a clients network ID (i.e Steam ID). Note that a clients network ID is not set on connect, you must wait for this callback before a users network ID is valid. The client name is passed into this function, you need to search the currently connected players to find the associated edict pointer. Note that the clients name can change between connect and id validation, you should use the entity index to track specific players.

Listening to Events

The IGameEventManager interface allows a plugin to listen to game events. Game events are fired by a Mod when things of interest happen, like a player dying or the bomb being planted. IGameEventManager::AddListener should be called to subscribe to game events. FireGameEvent is then called in your plugin when an event happens. The data contained in each event is described by event configuration files, in particular:

• hl2/resource/serverevents.res
• hl2/resource/GameEvents.res
• <mod dir>/resource/ModEvents.res

Creating ConVars and Commands

ConVars let you specify variables that users can use to configure the behavior of your plugin. ConCommands allow the creation of commands that your plugin provides. Creating both is easy and self contained, the code snippet below creates a new command empty_version and a new variable plugin_empty. These commands can be run from the server or client, you should use the index provided by SetCommandClient to determine the source of the command.

CON_COMMAND( empty_version, "prints the version of the empty plugin" )
{
        Msg( "Version:1.0.0.0\n" );
}

static ConVar empty_cvar("plugin_empty", "0", 0, "Example plugin cvar");

Interacting with Clients

The engine provides the IServerPluginHelpers interface to allow plugins to message clients. This interface provides a single function, CreateMessage that is called with 3 different dialog options to message users in different ways.

1. DIALOG_MSG, this prints a simple message to a client.
2. DIALOG_MENU, this provides a client with a menu of options.
3. DIALOG_TEXT, this shows a user a larger text field.

Examples of how to use this interface are shown in the sample plugin example. Each message will be displayed for 10 seconds in the HUD and for the menu and text option for up to 200 seconds in GameUI. Only 1 message can be displayed at a time, you have to wait for the current one to expire before a new one can be shown. Messages with a lower "level" field can be used to override current messages (the minimum level value is 0). Details of valid message fields can be found in the sample code.