PUBCOMP

Assured Publish Complete (part 3)

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 final message of the QoS 2 protocol flow. See the Protocol Flow section for more details.
 
 

Fixed Header

See the Fixed Header section for more information,
 
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

 

QoS level

The QoS level is not used for the PUBCOMP message.
 

DUP flag

The DUP flag is not used for the PUBCOMP messasge.
 

RETAIN flag

The RETAIN flag is not used for the PUBCOMP messasge.
 

Remaining Length

The Remaining Length is the length of the Variable Header (2 bytes)
This may be a multi-byte field. See the Fixed Header section for more details.
 

Variable Header

The Variable Header portion of the PUBCOMP message contains the same Message Identifier as the PUBREL message that is being acknowledged.

See the Variable Header section for more information.
 
 
bit
7
6
5
4
3
2
1
0
byte 1
Message Identifier MSB
byte 2
Message Identifier LSB

 

Payload

NONE
 

Actions

Upon receipt of a PUBCOMP message, the client can discard the original message, as it has been successfully delivered, exactly once, to the broker. For more discussion on actions to be performed, see the Protocol Flow section.

Discussion

ASC on DUP flag
The protocol flows for QoS2 do not require the use of the DUP flag, so it has been dropped.
ASC on naming
This is the message formerly known as PUBACK3
ASC on message mnemonics
PUBACK1, 2 and 3 are rather boring names for these messags. Can we think of more meaningful names?
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Last Modified: 19-Oct-99