mycelium/docs/packet.md

Packet

A Packet is the largest communication object between established peers. All communication is done via these packets. The packet itself consists of a fixed size header, and a variable size body. The body contains a more specific type of data.

Packet header

The packet header has a fixed size of 4 bytes, with the following layout:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |                    Reserved                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The first 8 bits are used to indicate the type of the body. 0x00 indicates a data packet, while 0x01 indicates a control packet. The remaining 24 bits are currently reserved, and should be set to all 0.