The PINGREQ message is an "are you alive" message that is sent from or received by a connected client.
The table below shows the fixed header format.
bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
---|---|---|---|---|---|---|---|---|
byte 1 | Message Type (12) | DUP flag | QoS level | RETAIN | ||||
1 | 1 | 0 | 0 | x | x | x | x | |
byte 2 | Remaining Length (0) | |||||||
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
The DUP, QoS, and RETAIN flags are not used.