Hi there,
Plesk does use a non-standard port I'm afraid. It uses port 8443. The main control panel is accesible over port 80, however this does not give you much control in relation to
plesk or logging into the
VPS
If you have access through the ports
SSH uses (for a linux
VPS) or remote desktop (on windows) then you could access the
VPS directly as you would indeed have full control in your own
VPS.