Network connectivity is more fickle than just checking for a service. It can come and go dynamically. You wander in and out of range of a Wi-Fi base station. You plug in or remove the USB networking adapter. The cleaning crew temporarily—or perhaps permanently—unplugs the Ethernet cable because it prevents them from vacuuming the floor.

https://devblogs.microsoft....0201102-00/?p=104411
Даже Рэймонд Чен в своё время пострадал от выдернутых шваброй шнурков!