When to use message vs subscribe callback method to receive published data ?

[luan-dang-techlabs]

New to MQTT , trying to understand when you use 'message' callback to receive message vs 'subscribe' method to receive published method.

1. If I use both 'message' and 'subscribe' callback, does that mean i will receive in both places via published?

[robertsLando]

The subscribe callback is called with the subscription result, it tells you if there was an error on subscription or not. The message callback is called everytime a message is received.

Then there is also the client.handleMessage(packet, done) function that can be used to handle messages with backpressure support (the next message that comes is not processed until you call done callback.

[luan-dang-techlabs]

thanks - i see what you mean now. some reason i thought subscribe's callback has the payload from publish, but message callback is used to receive payload.