MQTT Publish (ESP32) and Subscribe (Paho software client)

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falbriard
 
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MQTT Publish (ESP32) and Subscribe (Paho software client)

Post by falbriard »

I've successfully connected an MQTT topic in an Adafruit "io" feeder, loaded the data by an “UIflow” using the MQTT topic's publish function. I also was able to connect a MQTT PAHO client written in a Python code, using a subscribe function for my topic: “myuserid/feeds/myqueue/json”.

As long there is a real-time situation, I see the MQTT message recording in the feed, as well as the data reception at the client. There remains two open questions, regarding the following scenarios:

. Why the Adafruit feed (acts as MQTT broker) does not delete the records once the subscribed data was successfully delivered by the MQTT protocol. Is this possible by a setup option?

. What happens when a MQTT subscriber temporarily goes “off-line”? Is it possible to receive records written in past reading it from the feed queue? Is this available as an automatic process in order to synchronize the subscriber without any data loss?

Thanks for guidance.

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brubell
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Re: MQTT Publish (ESP32) and Subscribe (Paho software client

Post by brubell »

. Why the Adafruit feed (acts as MQTT broker) does not delete the records once the subscribed data was successfully delivered by the MQTT protocol. Is this possible by a setup option?
You may disable feed history from the feed page itself on io.adafruit.com/feeds/
. What happens when a MQTT subscriber temporarily goes “off-line”? Is it possible to receive records written in past reading it from the feed queue? Is this available as an automatic process in order to synchronize the subscriber without any data loss?
You can - please see this documentation about retained values here: https://io.adafruit.com/api/docs/mqtt.h ... ned-values

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falbriard
 
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Re: MQTT Publish (ESP32) and Subscribe (Paho software client

Post by falbriard »

Thanks a very precise answer. It helped to identity the reason for the data loss. This is a known and pending issue at the UIFlow software, as there is yet missing the support for the retain flag. Hope the M5stack team will fix this soon.

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