Windows 10 → Start → Windows Administrative Tools → Resource Monitor
This will start you in the Overview tab of the Resource Monitor
In the Processes with Network Activity section, left-click the column title image to sort it alphabetically
Scroll down until you find Diablo III64.EXE and tick the box to its left
This will now put it to the top of the column
Now click the Network tab and you should see something like this…
Now, choose your hero and start a game. This will cause the client to select one of the available servers in the farm for your game to be hosted on. Once your hero is in-game, alt tab back to Resource Monitor and you’ll see an extra connection, like this…
Now, have a look in this thread for the list of servers and whether the IP address your game is hosted on is one of the known good, or known bad, servers. If it’s a known good server, your clearance should be recorded. If it’s a known bad server, leave the game and repeat the process until you get a known good server.
If you get a server that’s not in the list, and you’re willing to risk it, get a clearance and update the thread with whether that IP address was a working one or not.