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A2S Query protocol

Learn about the A2S Query protocol, a popular method for game clients to discover available servers.
Read time 1 minuteLast updated 3 days ago
A2S is a UDP-based game server query protocol that Valve Software keeps 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 Multiplay Hosting, you must configure at least the following variables: It’s important to make sure the values reported for 
Players
and 
Max Players
in 
A2S_INFO
responses are correct. Multiplay Hosting uses these values to calculate and watch resource usages on the machine. If the values are inaccurate or in the wrong format, Multiplay Hosting won’t be able to manage resources, which can cause errors, game server crashes, or sub-optimal performance. The recommended best practice is to include correct map type data, which enables Multiplay Hosting to report crashes by map type.