To send data from a web-connected device like a point-of-sale system to Google Analytics, what would you use?
The Networking Protocol
The Measurement Protocol
The Measurement Protocol lets you send data to Analytics from any internet-connected device. It’s particularly useful when you want to send data to Analytics from a kiosk, a point of sale system, or anything that is not a website or mobile app
Read more here: https://support.google.com/analytics/answer/6086079