# Sensor/Topic Debugging using the Listener Command

The uORB is an asynchronous publish() / subscribe() messaging API used for inter-thread/inter-process communication. The listener command can be used from the QGroundControl MAVLink Console to inspect topic (message) values, including the current values published by sensors.


This is a powerful debugging tool because it can be used even when QGC is connected over a wireless link (e.g. when the vehicle is flying).


The listener command is also available through the System Console and the MAVLink Shell.


The listener command is only available on NuttX-based systems (Pixhawk, Pixracer, etc.) and Linux / OS X.

The image below demonstrates QGroundControl being used to get the value of the acceleration sensor.

QGC MAVLink Console

For more information about how to determine what topics are available and how to call listener see: uORB Messaging > Listing Topics and Listening in.