Network Protocol

Wire format, RPC ids and compatibility notes.

Knight speaks the SA-MP 0.3.7 wire protocol, including the 0.3.DL additions. It is byte-compatible with the official client, so no client patch is needed.

Transport

• UDP with the RakNet legacy offline handshake (cookie + auth key).
• Obfuscation: the server port masks the encryption key.
• Reliable ordered channels 0–31, unreliable and unreliable-sequenced packets.
• Payload fragmentation above the MTU with reassembly.

Connection handshake

client                 server
  | OpenConnectionRequest1 -> |
  | <- OpenConnectionReply1   |
  | OpenConnectionRequest2 ->
  | <- OpenConnectionReply2   |  (cookie challenge)
  | ConnectionRequest      ->
  | <- AuthKey                |  (GPCI serial challenge)
  | AuthKey(response)      ->
  | <- ConnectionAccepted     |
  | NewIncomingConnection  ->
  | RPC_ClientJoin (25)    -> |  version, name, serial, version string
  | <- RPC_InitGame (139)     |  hostname, limits, vehicle models

Key RPCs

Client versions

Knight reads the version from ClientJoin and only sends custom-model RPCs to 0.3.DL clients. Older clients receive base models instead.

Text encoding

SA-MP strings are Windows-1252. Knight encodes gamemode UTF-8 strings to CP1252 on the wire and decodes incoming text back to UTF-8.