For safety reason, it's impossible to expose the system to the public internet, we can only use the "push" strategy to report the up status. This tool is just for this purpose: request an URL at some interval repeatedly.
Recommend to use this with uptime-kuma (https://github.com/louislam/uptime-kuma)
[1] https://github.com/louislam/uptime-kuma
[2] https://ntfy.sh/
Uptime Kuma is one of the few open-source projects that feels like a commercial product: polished user experience, frequent release cadence, and a rich set of features including monitoring PostgreSQL servers, Docker containers, and so much more. Its list of supported notification services is so long that I don't even recognize half of the options available. Truly impressive.
Side note and shameless plug… We love Uptime Kuma so much that we made it one of the cornerstone applications provided by Fortressa, which we think of as the “App Store for Open Source”: https://fortressa.com/