Module mqttsn 

MQTT-SN (MQTT for Sensor Networks) layer implementation.

Implements MQTT-SN v1.2 packet parsing as a zero-copy view into a packet buffer.

Header Format

MQTT-SN uses a variable-length header:

Short form (length 2..=255):
  Byte 0:    Length (1 byte)
  Byte 1:    Message Type (1 byte)
  Byte 2+:   Message body (variable)

Extended form (length 256..=65535):
  Byte 0:    0x01 (marker)
  Byte 1-2:  Length (2 bytes, big-endian)
  Byte 3:    Message Type (1 byte)
  Byte 4+:   Message body (variable)

Flags Byte (used in CONNECT, PUBLISH, SUBSCRIBE, etc.)

Bit:     7     6-5    4      3     2         1-0
Field:   DUP   QoS    RETAIN WILL  CleanSess TID_TYPE

Message Types

Value	Name
0x00	ADVERTISE
0x01	SEARCHGW
0x02	GWINFO
0x04	CONNECT
0x05	CONNACK
0x06	WILLTOPICREQ
0x07	WILLTOPIC
0x08	WILLMSGREQ
0x09	WILLMSG
0x0A	REGISTER
0x0B	REGACK
0x0C	PUBLISH
0x0D	PUBACK
0x0E	PUBCOMP
0x0F	PUBREC
0x10	PUBREL
0x12	SUBSCRIBE
0x13	SUBACK
0x14	UNSUBSCRIBE
0x15	UNSUBACK
0x16	PINGREQ
0x17	PINGRESP
0x18	DISCONNECT
0x1A	WILLTOPICUPD
0x1B	WILLTOPICRESP
0x1C	WILLMSGUPD
0x1D	WILLMSGRESP
0xFE	ENCAPS_MSG

Re-exports

pub use builder::MqttSnBuilder;

Modules

builder

MQTT-SN packet builder.

Structs

MqttSnLayer

MQTT-SN layer – a zero-copy view into a packet buffer.

Constants

ADVERTISE

CONNACK

CONNECT

DISCONNECT

ENCAPS_MSG

GWINFO

MQTTSN_MIN_HEADER_LEN

Minimum MQTT-SN header: 1 byte length + 1 byte type.

MQTTSN_PORT

Default MQTT-SN UDP port.

PINGREQ

PINGRESP

PUBACK

PUBCOMP

PUBLISH

PUBREC

PUBREL

RC_ACCEPTED

RC_REJ_CONGESTION

RC_REJ_INVALID_TID

RC_REJ_NOT_SUPPORTED

REGACK

REGISTER

SEARCHGW

SUBACK

SUBSCRIBE

TID_NORMAL

TID_PREDEF

TID_SHORT

UNSUBACK

UNSUBSCRIBE

WILLMSG

WILLMSGREQ

WILLMSGRESP

WILLMSGUPD

WILLTOPIC

WILLTOPICREQ

WILLTOPICRESP

WILLTOPICUPD

Statics

MQTTSN_FIELD_NAMES

Field names for the MQTT-SN layer.

Functions

decode_mqttsn_length

Decode the MQTT-SN variable length field.

is_mqttsn_payload

Check if a UDP payload looks like an MQTT-SN packet.

message_type_name

Get the human-readable name for a message type.

return_code_name

Get the human-readable name for a return code.