Monitoring the external interface (UL / DL) of a Keenetic router in a desktop widget (Rainmeter Plugin)

Once, I wanted to see a graph of my Keenetic Viva (KN-1910) router's WAN channel load right on my Windows 10 desktop.

Having found no ready-made solutions, I started looking for a desktop widget program that would let me create custom widgets. I liked the open-source program Rainmeter.

After reading the documentation on creating widgets (called "skins" in their terminology) and external plugins, I wrote a plugin in C++. The plugin communicates with the router via a REST API.