emqx/apps/emqx_bridge_syskeeper/doc/protocol_v1.md

Table of Contents

1. Packet Format
2. Common Header
   1. Types
   2. Shared Flags
3. Handshake Packet
4. Forward Packet
   1. Flags
   2. Payload
      1. Message Content map structure
5. Heartbeat Packet

Packet Format

bytes	0	1	2	3	5	6 .. end
	variable length				common header	payload

The length of the remaining part(common header + payload) is indicated by the Length Header of each packet

Common Header

bits	0	1	2	3	4	5	6	7
	packet type				shared flags

Types

type	usage
0	handshake
1	forward
2	heartbeat

Shared Flags

The usage of each bit is determined by the type of packet

Handshake Packet

bytes	0	1
	common header	version

Forward Packet

bits	0	1	2	3	4	5	6	7	...
	packet type							ACK	payload
					forward flags

Flags

flag	usage
ACK	This packet need a ACK response

Payload

bytes	0	..	n	n+1	..	x
	Content Length			Message Content

• Content length is a variable length number.
• Message content is a list in an opaque binary format whose element is a map structure

Message Content map structure

{
  id: "0006081CCFF3D48F03C10000058B0000", // unique message id
  qos: 1,
  flags: {dup: false, retain: false},
  from: "clientid",
  topic: "t/1",
  payload: "hello, world",
  timestamp: 1697786555281
}

Heartbeat Packet

bytes	0
	common header