Forward /dev/input/js0 from control station to robot

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Is there a way for me to write the events to a file similar to the /dev/input/js0 file so that ROS Joy can utilize it?

yes: keep the binary format that you read from /dev/input/js0 and use something like uinput to inject it into the kernel of your control station. Alernatively use socat (or a similar tool) to pipe /dev/input/js0 (on your control station) to a socket on your on-board PC (similar to this). Then have joy open that socket instead of an actual device.

Other than that I would say you have two options:

1. publish Joy msgs on your control station and subscribe those on your on-board pc
2. use a custom node running on your on-board pc, that, through a custom protocol, gets joystick event data and then publishes it as Joy msgs there