MQTT: Wildcard support

[arunvtec]

Hello,

Does the ESP-MQTT support wildcard in the MQTT topic? Is there an example on this?

I published the topic -

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/multisensor/device-ID/measurements/temperature/GET

and it works fine.

But with wildcard in the topic

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/multisensor/+/measurements/temperature/GET

, there is no response. 'mqtt_event_handler' is never called.

Thanks,
Arun

[ESP-Marius]

Which version are you running (IDF and MQTT)?

It worked fine when I tested it right now with the master branch and a local Mosquitto broker.

Subscribing to

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/topic/+/esp32

and then publishing to

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 /topic/qos0/esp32

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 /topic/qos1/esp32

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/topic/qos2/esp32

gives me the expected result. I receive the data from all the published messages.

Could it be that your broker doesn't support wildcards?

[tommeyers]

I have a feeling that the OP is publishing a wildcard not subscribing with a wildcard. OP what do you say. Sorry if I am wrong.

[ESP-Marius]

I have a feeling that the OP is publishing a wildcard not subscribing with a wildcard. OP what do you say. Sorry if I am wrong.

Re-reading the question I see that you are probably right.

OP: if you are trying to publish with a wildcard then the answer is that this is not a part of the MQTT spec.

It says that:

The Topic Name in the PUBLISH Packet MUST NOT contain wildcard characters

Although technically there should be nothing in the esp MQTT client preventing you from publishing to an invalid topic, we don't do any checks on the content of the topic, but a well-behaving broker will probably close the connection.

[tommeyers]

One other suggestion:

My MQTT broker (mosquitto) gives me some tools for debug and monitor:

I can start the broker with verbose logging and see all kinds of events

There is a generic subscriber

There is a generic publisher.

Good tools for an MQTT developer.

Tom Meyers