3.6 PUBREL - release version (release received QoS 2, Part 2)
PUBREL PUBREC packet is a response packet. It is the third QoS 2 data exchange protocol packets.
3.6.1 Fixed Header fixed title
FIG 3.16 - PUBREL fixed packet header
| Place |
7 |
6 |
Fives |
4 |
3 |
2 |
1 |
0 |
| Byte 1 |
MQTT control packet type (6) |
reserved |
||||||
|
|
0 |
1 |
1 |
0 |
0 |
0 |
1 |
0 |
| Byte 2 |
The remaining length (2) |
|||||||
|
|
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
PUBREL fixed control packet header and 3,2,1 0 Reserved, must be set to 0, 0 and 0, respectively. The server must be treated as any other value malformed and network connections turned off [the MQTT-3.6.1-1] .
The remaining length field
This is a variable length header. For PUBREL packet, a value of 2.
3.6.2 Variable Header variable header
Variable header contains packet being acknowledged PUBREC same packet identifier.
FIG 3.17 - PUBREL packet header variables
| Place |
7 |
6 |
Fives |
4 |
3 |
2 |
1 |
0 |
| Byte 1 |
MSB packet identifier |
|||||||
| Byte 2 |
LSB packet identifier |
|||||||
3.6.3 Payload Payload
PUBREL packet no load.
3.6.4 Actions Action
This is described in detail in Section 4.3.3.