How To Turn Off Your Monitor Via Command Line in Ubuntu

It turns out the solution is very simple. The xset command is the X server preferences command.
It has a simple command to turn off the monitor:

$ xset dpms force off

and to turn the monitor back on:

$ xset dpms force on

You can also check the status of the X server settings by using:

$ xset -q

Source: How To Turn Off Your Monitor Via Command Line in Ubuntu | systemBash