Protocol:Packet Header

Different versions of PSO use slightly different formats for the headers on all packets sent to and from the server. PSO versions up to, and including, PSOGC use a 4-byte header, while PSO Blue Burst uses an 8-byte header. All packets should generally be some multiple of their header in size (since that's how the encryption is dealt with).

Note that some versions (namely, Japanese Dreamcast v1) of the game do silly things and send packets that aren't multiples of the header size on some occasions.

Dreamcast/Gamecube Header Format

Bytes	Meaning
0x00	Packet Type
0x01	Flags
0x02-0x03	Packet Size (Little-Endian)

PC Header Format

Bytes	Meaning
0x00-0x01	Packet Size (Little-Endian)
0x02	Packet Type
0x03	Flags

Blue Burst Header Format

Bytes	Meaning
0x00-0x01	Packet Size (Little-Endian)
0x02-0x03	Packet Type (Little-Endian)
0x04-0x07	Flags (Little-Endian)