Delete retained messages

#1

Hello,

Is there a way to delete retained messages in the broker?
I tried deleting the stashed messages, but the retained messages aren’t deleted.

Thanks!

#2

Have you tried clicking on the following button?

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#3

Thank you for your answer, I don’t mean this messages.

When a client subscribes to a topic, if there are retained messages, the client receives the last retained message. I want to delete those retained messages so when the client subscribes to the topic doesn’t receive anything until something new is published.

#4

Buff! Sorry for the confusion, certainly “unconfirmed” is not the same as “retained”.

To clear those retained messages you can use standard MQTT method which is to send a PUBLISH message with the topic to clear with retain flag enabled and zero payload. That will trigger:

    http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html
    [MQTT-3.3.1-10] A PUBLISH Packet with a RETAIN flag set to 1 and a payload containing zero bytes will be processed as normal by the Server and sent to Clients with a subscription matching the topic name. Additionally any existing retained message with the same topic name MUST be removed and any future subscribers for the topic will not receive a retained message

At the same time, we will pass an indication to programming to see if it is possible to implement a retained inspector to better track and clear retained messages in your MQTT HUB.