This message is either the response from the broker to a PUBREL message from a publisher, or the response from a subscriber to a PUBREL message from the broker. It is the fourth and last message in the QoS 2 protocol flow.
The table below shows the fixed header format.
bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
---|---|---|---|---|---|---|---|---|
byte 1 | Message Type (7) | DUP flag | QoS level | RETAIN | ||||
0 | 1 | 1 | 1 | x | x | x | x | |
byte 2 | Remaining Length (2) | |||||||
0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
The variable header contains the same Message ID as the acknowledged PUBREL message.
bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
---|---|---|---|---|---|---|---|---|
byte 1 | Message ID MSB | |||||||
byte 2 | Message ID LSB |