Good. So the switch works.
Now connect the BrewTroller to the switch and fire it up. Initiate communications between the RPi and the BrewTroller. Then open a terminal on the RPi and ping the IP address of the BrewTroller. Let the ping run for a while, say 20-30 seconds. We are looking for 0 lost messages, just like we've seen between the RPi and the Internet so far.
I'm off to my monthly brew club meeting.
If the ping comes back with errors, run
nmap <BrewTroller IP Address>
and
traceroute <BrewTroller IP Address>
and report what they return.
If the ping comes back clean, it looks like you have a good network between the RPi and the BrewTroller. I suggest doing a mock brew (brewing water) and controlling the BrewTroller exclusively from the RPi.
If that works, start controlling it from an external device.
I'm anxious to see how this all turns out. There is no reason for the communication between the RPi and the BrewTroller to be anything but 100% reliable. If any of these steps turn up a problem, we'll backtrack and figure it out. This stuff is pretty straight forward if you go step by step.