I have Plex on a Fire Stick attached to one tv and Plex on my second streamer, a Roku, as well as an iPad. All devices are on the same aforementioned (network) wifi hotspot.
So, under this arrangement, will the Plex apps on the Fire, Roku and iPad, treat the connection as local,
or will I be using my internet data ?
Do you need remote access to your server? If not just set up a router or switch and connect everything to it. It won’t have internet access but if all you need it for is local playback that should make for a much better experience. If the little hotspot has an ethernet port (I doubt it, but you never know) You may even be able to feed that into said router or switch. I honestly don’t know how one of those hotspots would handle what we would call local traffic.
Monitor playback via Plex Dashboard → Now Playing. Make sure the connection is Local, not Remote or Indirect.
If the connection is Indirect, then it is definitely using your Internet data. Indirect connections use Plex Relay and are tunneled through servers at Plex. It also means something is wrong with your network setup if a local server & client have an indirect connection.
Contact AT&T and verify how they measure data and traffic. If they can view stats in real time, stream a movie and ask what they see on their system. Their might be an online customer portal or app where you can view stats yourself.
In theory, streaming from a local Plex server to a local Plex client is no different than printing to a WiFi printer or accessing a WiFi attached file server. However, it is still best to verify with AT&T regarding how they count data packets through the hotspot.
