Universal Robots+

How externalcontrol urcap sends data to remote PC with ros driver


I am trying to understand how ros gets data from the externalcontrol urcap. I looked at ros hardware_interface_node.cpp at Universal_Robots_ROS_Driver package. I saw that there is a loop and at each iteration ros receives datapackage from externalcontrol urcap. I looked at the java code of external_controller fromhttps://github.com/UniversalRobots/Universal_Robots_ExternalControl_URCap/tree/master/src/main/java/com/fzi/externalcontrol/impl. I haven’t found any sending of any datapackages. I saw only gathering a urscript code that ros sends and sending to the controller for execution.
Can you explain how the urcap sends data, for example joints states to /joint_states topic?

Thanks in advance.

As a quick answer: I wrote a tiny bit of the details here: https://github.com/UniversalRobots/Universal_Robots_ROS_Driver/tree/master/ur_robot_driver