PUBREC packet - Publish received (QoS 2, part 1).
MQTT 5.0 §3.5
Readonly
Packet identifier
Optional
PUBREC properties (5.0)
Reason code (5.0, defaults to 0x00)
Packet type discriminator.
PUBREC packet - Publish received (QoS 2, part 1).
See
MQTT 5.0 §3.5