I've got a solar panel system with a Growatt inverter. The system has a monitoring platform. To connect the inverter to the internet to let it communicate with the monitoring portal, you need a "data logging stick". This stick is an apart (optional an relatively cheap) device you plug into the USB port on the inverter. The stick comes in multiple types, like Wifi, LAN, and GPRS. I've got a Wifi stick.
The stick sends data to the server every 5 minutes. But I came to the conclusion that the system is capable of two-way communication. In the app you have options to change settings of the inverter. When you do this, a command is sent to the inverter. This works regardless of wether your phone is in the same wifi network or just has internet through another way. In addition, it seems that the support can remotely operate/update/read the inverter. How can this work while the end-user (me) never had to change any router configuration or the like. And what about security?