How to test for the client to be connected or not?

[SiebrenW]

I'm looking to use Boost::MQTT5 for my application, an embedded device communicating with other devices, but I kind of need to know (preferably also on a callback) whether the client has been connected/disconnected.

My current application uses mosquitto and asio, making the interface between the two a common pain point. My abstraction was easy to convert, but the missing part seems to be the on_disconnect/on_connect callbacks.

The application has different behaviour based on the connection (ie: stop sending more messages and create a safe state/recover)

So is there such a thing, or should I keep looking?

[biljazovic]

Connection state can be observed via a custom logger object. On a successful connection, the on_connack callback is invoked. For disconnection, the at_transport_error callback can be used. For example, if no packets are received from the broker for 3 * keep_alive / 2 seconds, at_transport_error will be triggered with boost::asio::error::timed_out.

See also #45 (comment)