A2S query protocol

A2S is a popular UDP-based game server query protocol that Valve Software maintains as a part of the Steam SDK. Many game engines support A2S natively, but if yours doesn’t, you can add support for A2S manually by using one of the A2S libraries for your preferred language (for example, go-a2s for Golang, QueryMaster for C#).

Visit the Valve Software wiki page for server queries to learn more about the technical details of the A2S protocol, including the protocol specification, response body format, and a list of implementations in various languages.

To integrate a manual A2S implementation with Game Server Hosting (Clanforge), you must configure at least the following variables:

It’s important to ensure that the values reported for Players and Max Players in A2S_INFO responses are accurate. Game Server Hosting uses these values to calculate and monitor resource usages on the machine. If the values are inaccurate or in the wrong format, Game Server Hosting won’t be able to manage resources properly, which can cause errors, game server crashes, or sub-optimal performance. Game Server Hosting recommends that you also provide accurate maptype data, which allows us to report crashes by maptype.

Note: A2S is a legacy protocol. Unity’s SQP protocol is newer and integrates more easily into the Unity ecosystem.