Arma3 Server Browser v3 and DayZ Server Browser v2 Protocols

Both protocols are designed for server information transmission and share a similar structure, differing only in minor details. They are implemented as nested sub-protocols within the Steam A2S_RULES protocol. The keys encode chunk metadata (current index and total count), while the values store the actual chunks.

Server details are transmitted through the A2S_RULES protocol in messages formatted as described below.

During decoding, the parser replaces these escape pairs with their original bytes:

• {0x01, 0x01} -> 0x01
• {0x01, 0x02} -> 0x00
• {0x01, 0x03} -> 0xFF

During encoding, AppendEscapeSequences applies the inverse mapping:

• 0x01 -> {0x01, 0x01}
• 0x00 -> {0x01, 0x02}
• 0xFF -> {0x01, 0x03}

After escaping, EncodePages splits the message into ordered fragments and places them into A2S_RULES key-value pairs. A page size of zero selects the documented default of 124 bytes.

If the entire message exceeds 1400 bytes (the maximum size of a single UDP packet in the Steam API), some data must be truncated. However, in practice, a buffer of up to 8192 bytes is often sufficient, allowing servers to respond with all data in a single packet.

Background information: https://community.bistudio.com/wiki/Arma_3:_ServerBrowserProtocol3

Arma3 Server Browser v3 Protocol

DayZ Server Browser v2 Protocol