mirror of
https://github.com/meshtastic/meshtastic.git
synced 2024-11-13 17:14:25 -08:00
24 lines
1.3 KiB
Markdown
24 lines
1.3 KiB
Markdown
|
---
|
||
|
|
id: python-stream
|
||
|
|
title: Meshtastic-python stream protocol
|
||
|
|
sidebar_label: Stream Protocol
|
||
|
|
---
|
||
|
|
|
||
|
|
# Stream protocol
|
||
|
|
|
||
|
|
Documentation on how out protobufs get encoded when placed onto any stream transport (i.e. TCP or serial, but not UDP or BLE)
|
||
|
|
|
||
|
|
## Wire encoding
|
||
|
|
|
||
|
|
When sending protobuf packets over serial or TCP each packet is preceded by uint32 sent in network byte order (big endian).
|
||
|
|
The upper 16 bits must be 0x94C3. The lower 16 bits are packet length (this encoding gives room to eventually allow quite large packets).
|
||
|
|
|
||
|
|
Implementations validate length against the maximum possible size of a BLE packet (our lowest common denominator) of 512 bytes. If the
|
||
|
|
length provided is larger than that we assume the packet is corrupted and begin again looking for 0x4403 framing.
|
||
|
|
|
||
|
|
The packets flowing towards the device are ToRadio protobufs, the packets flowing from the device are FromRadio protobufs.
|
||
|
|
The 0x94C3 marker can be used as framing to (eventually) resync if packets are corrupted over the wire.
|
||
|
|
|
||
|
|
Note: the 0x94C3 framing was chosen to prevent confusion with the 7 bit ascii character set. It also doesn't collide with any valid utf8 encoding. This makes it a bit easier to start a device outputting regular debug output on its serial port and then only after it has received a valid packet from the PC, turn off unencoded debug printing and switch to this
|
||
|
|
packet encoding.
|