Safely wake up black VNC screen cloud servers

Question

What is the safest way to wake up a cloud server (Windows & Linux) via VNC using the keyboard.

Looking into a taking a screen grab of a large number of servers (Windows & Linux) using the below Python library, what benign keystrokes I can send?

https://github.com/sibson/vncdotool

Answer 1

Actually it is enough to press the shift key. That shouldn't enter any key presses that change anything on screen but it is enough to wake up the screen saver.