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hayderr · Posted: Tue Jul 29, 2008 1:42 pm Post subject:

Hello all,
I have a question around MQTT. I am using a Broker application that publish messages using MQTT.
I am using Quality of Service (QoS) 2.
The communication between the Publisher (Broker) and the Client is through a GPRS network. The protocol flow as follow:
1- Broker sends PUBLISH command
2- Client sends PUBREC message
3- Broker sends PUBREL
4- Client sends PUBCOMP
Sometimes, when the broker sends a Publish message the client receives it, but due to network load, the PUBREC message takes a long time to get to the Broker. So the Broker will send the message again, because it assumes there was a failure. In this case the client will have a duplicate message.
I would like to know how can I change the retry timer to make it longer? I have read the Broker and they say "The time delay (retry interval) before resending a message that has not been acknowledged is specific to the application, and is not defined by the protocol specification." How can I do this in my application?
Thank you

Hayder