Gunz Packet Structure

             Packet
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/  ===========================  \
/  |      -- Header --       |  \
/  |  [uint16_t] version     |  \
/  | *[uint16_t] fullSize    |  \
/  |  [uint16_t] checksum    |  \
/  ---------------------------  \
/  |      -- Payload --      |  \
/  | *[uint16_t] dataSize    |  \
/  | *[uint16_t] commandID   |  \
/  | *[uint8_t ] packetID    |  \
/  | *[ Buffer ] parameters  |  \
/  ===========================  \
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If a member has a * beside it, it will be encrypted when version == 0x65. These must be passed off to the decrypt() function in the crypto module for processing.

version: The version is 0x64 for unencrypted packets, and 0x65 for encrypted packets. There is an extra decryption step when a packet with a version of 0x65 is encountered.

fullSize: The full size of the packet, including the header.

checksum: This value is set to zero during packet construction, then, once everything else is filled in and the packet is encrypted if necessary, the checksum algorithm in cockpit/src/packet/crypto.cpp is used to update this parameter.

dataSize: The size of the packet’s payload. This can be expressed as sizeof(packet) - sizeof(header). My guess is that this is provided to potentially expand the header’s data structure; but that’s just a guess.

commandID: Each packet has a registered commandID. This is shipped off to the appropriate packet::Registry’s dispatch method for processing.

packetID: A counter, incrementing by one every time a packet is sent out to the client. Since it’s only 8 bits wide, an overflow wraps the counter back around to zero. No biggie. It starts out at 1, but I have a feeling the starting number is totally arbitrary.

parameters: All the packet’s parameters, serialized and concatenated in left-to-right order.