What is the REVERSE_PORT?

In these instructions: GitHub - ros-industrial/universal_robot: ROS-Industrial Universal Robots support (http://wiki.ros.org/universal_robot) to bring up the robot it says to execute this command:

roslaunch ur_bringup ur5_bringup.launch robot_ip:=IP_OF_THE_ROBOT [reverse_port:=REVERSE_PORT]

Is the REVERSE_PORT documented somewhere? What is the port I should use?

Thank you in advance for your help!

The launchfile you are mentioning is deprecated. For using a UR robot with ROS, please use the ur_robot_driver with its according launch files. Use that driver together with GitHub - ros-industrial/universal_robot at melodic-devel-staging or GitHub - fmauch/universal_robot at calibration_devel. As this driver also uses a reverse port, I’ll add an explanation below.

The reverse_port is opened by the driver’s reverse interface which establishes a custom communication protocol between the driver and the robot. This does not have to be changed necessarily, only if the default value does not suffice.

Changing the reverse port can be necessary e.g. when starting multiple driver instances on one control PC (as then each driver instance has to open its own reverse port) or when there is another application already using the default reverse port 50001.

Thank you for your quick reply and help!