[dudik]

Thank you, but I don't use a notification server.

[Spivak]

Nothing is stopping you, even if you don't run any kind of GUI session: https://github.com/Sweets/tiramisu

[yipbub]

notify-send is for desktop(possibly gnome only?) notifications.

[jlgaddis]

notify-send works by sending notifications to a notification daemon (a.k.a., a "notification server", as defined in the "Desktop Notifications Specification").

notify-send won't work for dudik since, as he said, he doesn't use a notification server.