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Reconnecting the Mqtt client after network failure - receives the previously received messages again [message #1751457]

Tue, 10 January 2017 14:15

Kaveri Hindi

Messages: 5
Registered: January 2017

Junior Member

Hi All,

I am using paho for Mqtt connection
I have subscribed to few topics and I am able to receive the messages properly.

In case of poor network or no network, Mqtt connection is lost. So I am trying to reconnect to Mqtt with the same client and subscribe to the same topics.
After reconnecting I am receiving the previously received messages again. (last message on each topic)

I am hoping if its the previously connected client, It shouldn't receive the previously received messages again after reconnecting.

How should i handle this case if I don't want to receive the previously received messages.

I am not using any unique identifier for any messages recieved.

Hoping for a positive reply !
Thanks in advance

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Re: Reconnecting the Mqtt client after network failure - receives the previously received messages a [message #1752000 is a reply to message #1751457]

Tue, 17 January 2017 15:36

James Sutton

Messages: 71
Registered: July 2015

Member

Could it be that you are publishing the messages with the retain flag set? If you want messages to be retained, you will need to disable clean session when you reconnect your client.

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Re: Reconnecting the Mqtt client after network failure - receives the previously received messages a [message #1752171 is a reply to message #1752000]

Thu, 19 January 2017 12:46

Kaveri Hindi

Messages: 5
Registered: January 2017

Junior Member

We want to ensure that messages are NOT re-delivered to the clients upon reconnection.
How do we ensure the same ? Either avoid redelivery or detect duplicates.

We are using configurations 1) Clean Session as false 2) with QOS = 1 3) retain flag to true. While reconnect also , we use the same client Id.
We have RabbitMq as the Mqtt broker.

Please guide how to avoid redelivery or detection of duplicates mqtt messages. Does QOS = 2 work with RabbitMq ?

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