Install x11vnc by entering the following commands in the terminal:
sudo apt update sudo apt install x11vnc
Description:
VNC server to allow remote access to an existing X session
x11vnc allows one to view remotely and interact with real X displays (i.e. a display corresponding to a physical monitor, keyboard, and mouse) with any VNC viewer. It has built-in SSL encryption and authentication, UNIX account and password support, server-side scaling, single port HTTPS and VNC, mDNS service advertising, and TightVNC and UltraVNC file-transfer.
Homepage: http://www.karlrunge.com/x11vnc/
Version: 0.9.13-3
Section: universe/x11