Source® game servers are the means by which people are able to play certain multiplayer games online. Any game that is built on the Sourge® engine and is capable of online play uses this kind of server. It is possible to install a Source® game server on a personal computer that makes use of a regular Internet connection, though game service providers (GSPs) typically rent them as well. These servers can be installed manually, though it is also possible to use a free program known as the Half-Life dedicated server (HLDS) update tool to download, update, and set up the necessary files. Using this tool, a Source® game server can be created without needing to own the game in question.
First introduced in 2004, the Source® game server uses a fairly standard client-server basis for online gaming. In this type of relationship, the server computer is responsible for calculating all of the various relationships between in-game objects. Client computers connect to the server, which processes their inputs and then returns the results. If there is ever any discrepancy between the server's version of game world and the version contained on a client, the server is considered authoritative. This can lead to discrepancies in high lag situations, such as poor hit detection.
There are two different kinds of Source® game servers, which are differentiated based on the type of install. A dedicated Source® game server is the version that can be rented from GSPs, though it is also possible to perform such an install on a personal machine. Dedicated servers run independently from any clients and can remain operational regardless of whether anyone is connected. This kind of server can typically also be created without owning the game in question. The HLDS update tool can be used to obtain the server files for a range of Source®, GoldSrc, and third party games.
The other type of Source® game server is referred to as a listen server. In order to start this type of Source® game server, the game in question must be purchased and fully installed because the necessary option is usually contained within the menu. These servers are operated concurrently with a client version of the game so that one player serves as both a host and a client. Other clients can then connect to the server and play as normal. If the host stops playing, the listen server ceases to exist and the game will terminate.