Here's the open source program I am using to monitor disconnects. I can't promise it works perfectly but it is doing a good job for me. https://code.google.com/archive/p/internetconnectivitymonitor/. Source: almost 2 years ago

Internet Connectivity Monitor. This is Freeware, but hasn't been updated since a couple of years. https://code.google.com/archive/p/internetconnectivitymonitor/. Source: over 2 years ago

Try https://app.freshping.io/ instead, think is more reliable than uptimerobot. Or if you can run a custom script (with crontab) https://healthchecks.io/ is the way to go, here's an example script https://gist.github.com/1activegeek/9a932346d85d20123eb3a60d3b03a095. Source: almost 2 years ago

There are others. LogRocket does this for frontend monitoring, and there are also Freshping, Uptime, Logicmonitor,, all of which should tell you that the health of applications is really important! - Source: dev.to / almost 2 years ago