I found many posts about running x11vnc at boot up on various flavors of Ubuntu 16.04 (Xenial Xerus). None of the posted suggestions would work for me as-is. I ended up finding a solution that works on Xubuntu 16.04 (Xenial Xerus), so am posting just the Systemd service file here as a suggestion of what works for me:
I found myself trapped within a Vinagre Remote Desktop Viewer VNC session to a remote Linux server console. Trying all keys to find the magic key to pop mouse control back to my local Linux system, finally I found it: the F10 key! In the mean time, I had found the key to make the Vinagre on-line help come up, was navigating through it using keyboard only... and what few help suggestions there were, they always told to go to the Vinagre menu to click on something...
In this brief HOW-TO I will explain the steps necessary to get the popular VNC Server working on a Windows computer which has Comodo Free Firewall + Antivirus for Windows also installed on it.
First you will need to open the Comodo Free Firewall + Antivirus for Windows interface, click Firewall at the top, click Advanced on the left hand side of the window, next click Network Security Policy, click the tab for Global Rules, then click the Add button to add a new rule. Below is the window adding the new rule, with the first page of details already filled in: