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Are there any MQTT libraries that do not block while connecting?

I'm currently using PubSubClient, and the connection part contains this code: https://github.com/knolleary/pubsubclient/blob/master/src/PubSubClient.cpp 

        while (!_client->available()) {
            unsigned long t = millis();
            if (t-lastInActivity >= ((int32_t) MQTT_SOCKET_TIMEOUT*1000UL)) {
                _state = MQTT_CONNECTION_TIMEOUT;
                _client->stop();
                return false;
            }
        }

I'd like my main loop to continue, or a callback to be called, while the MQTT connection is established, rather than waiting for ages if the MQTT server is unavailable.

Update:

I wrote a modification to take a callback function, and called it in an else clause added to that if statement, and discovered that the blocking delay is not this while loop. I think it's in the _client->connect at the start of the method.

VE7JRO
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Stephen Denne
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1 Answers1

4

I had the same question and found an mqtt library that is completely non-blocking.

You need to manually install it and the docs give instructions:

It requires one additional library:

I also liked the example's use of the Ticker library as a general tool for non-blocking code.

Rudy Albachten
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