The IP you need to enter on
notochord startup is the one of your PC, where the Blender client will be running. It is le local IP address, the one that identifies it within your local network.
in order to find it:
open a command prompt window by [Win menu] > type the word: cmd
issue the command
the IP address will normally appear under the name: IPv4 Address
Linux & Mac
open a terminal window and issue the command
it will list the different network adapters available, if you are conneting with WIFI look for the one starting with w, like wlan0.
Zyzzxander "Could not communicate with wpa_supplicant"
Have you set your country as described here?