RoboRIO / FMS / mDNS / lessons learned

[Mr. Lim]

Having competed at GTRC last weekend, I noticed sometimes my students had a lot of difficulty getting a tethered connection to the robot in the pits, possibly due to some of the items raised in this thread.

It's still speculation at this point, but I think it has to do with stale DHCP leases from when the robot and DS were connected to the FMS (10.xx.yy.zz) vs falling back to link-local (169.254.xxx.xxx) in the pits.

If you are connected to the FMS and play a match, the DHCP server will give all your devices a 10.xx.yy.zz address. After leaving the field, when you power cycle the robot, or disable/enable the network connection on the DS, or wait an unspecified amount of time, those devices get a new 169.254.xxx.xxx link-local IP.

If you have one device that still has the IP from the FMS's DHCP, and another with the link-local, the two won't communicate.

The solution we stumbled up is to make sure the robot is power cycled, and the DS's network connection is disabled and re-enabled after every match (to refresh the DHCP lease).

Has anyone else run into this?