There is no need to use hostname, you can provide ip address of your rendezvous server.
The plug connects to the ntp server and synchronizes the time. At this point I have no idea what would happen if the plug did not have access to the internet.
If does have acces, every hour on the hour (eg 8:00, 9:00 ), plug sends the overall consumption data to the provisioning server. Actual power draw and partial consumption (past hour) is provided on request. Actual power consumption is provided on every single request, partial consuption data are availible each circa 5 minutes and more frequent request are rejected.