From EduVNC

Value

This is the port number the service will listen on. To access EduVNC from a browser you would visit the URL http://computertname:port. I.E. if the port value was 8080 then the URL would be http://computertname:8080

Registry Information

HKLM\Software\EduVNC contains ServiceName\Port which is the value of the box. Valid values are:

• Integers between 1 and 65535 inclusive.
• Not used by another started EduVNC service.
• Not conflicting with any other running service. See IANA Assigned Port Numbers for a list of potential conflicts.

Additional Notes

If there is a conflict between this services port and an already running service the start / stop button will instead read error. Change the port and then restart the service with the button and it should begin working. In some cases you many have to close and open EduVNC before to continue using that same service name.