Return values of `MqttClient::subscribe` not documented

[UchihaYuki]

auto result = mqttClient.subscribe(commandTopic);
Serial.printf("Subscription result %d\n", result);

Since there isn't doc yet I don't know what happened.

The MQTT broker I use is Mosquitto broker, I use it with Home Assistant. I set the version to 3.1.1. As far as I know, ArduinoMqttClient uses 3.1.1 as well. I don't know what happened so that subscribe failed. Or 1 means successful? But I haven't received any message from the broker.

[UchihaYuki]

I can observe the message gets sent to the MQTT broker by using MQTT Explorer. It's just my Arduino device can't receive the message.

[UchihaYuki]

I found the reason why I didn't receive any message because I forgot to call mqttClient.poll().

I just changed my MQTT broker, and this time I got a return code of 0 and can't receive any message.

[UchihaYuki]

Any updates on what return code 0 means?

[UchihaYuki]

After switching to pubsubclient, it works now. I also tried arduino-mqtt, it doesn't work either, but it at least gives me an error code, although the error code is not that helpful.