WebSphere Message Brokers
File: ac10990_
Writer: Kate Hostler

Reference topic

This build: July 31, 2007 21:18:10

PUBREL Assured Publish Release (part 2)

A PUBREL message is the response either from a publisher to a PUBREC message from the broker, or from the broker to a PUBREC message from a subscriber. It is the third message in the QoS 2 protocol flow.

Fixed header

The table below shows the fixed header format.

bit 7 6 5 4 3 2 1 0
byte 1 Message Type (6) DUP flag QoS level RETAIN
  0 1 1 0 x x x x
byte 2 Remaining Length (2)
  0 0 0 0 0 0 1 0
QoS level
Not used.
DUP flag
Not used.
RETAIN flag
Not used.
Remaining Length field
The length of the variable header (2 bytes). It can be a multibyte field.

Variable header

The variable header contains the same Message ID as the PUBREC message that is being acknowledged. The table below shows the format of the variable header.

bit 7 6 5 4 3 2 1 0
byte 1 Message ID MSB
byte 2 Message ID LSB

Payload

There is no payload.

Actions

When the broker receives a PUBREL message from a publisher, the broker makes the original message available to interested subscribers, and sends a PUBCOMP message with the same Message ID to the publisher. When a subscriber receives a PUBREL message from the broker, the subscriber makes the message available to the subscribing application and sends a PUBCOMP message to the broker.

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Copyright IBM Corporation 1999, 2007Copyright IBM Corporation 1999, 2007. All Rights Reserved.
This build: July 31, 2007 21:18:10

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