On boot, Marty will call a startup script which initialises the required ROS parameters, such as the required subscriber/publisher handles. From here, it will then initialise the core command server, calibrate the servos and open a port for handling incoming connections (for example from a remote computer).

ros_marty Documentation
Here you can find the documentation for the ros_marty stack

marty_msgs Documentation
Documentation for the messages used by Marty's ROS stack