If you are sitting at the internet side looking in, the chances are you will never know if it has been properly configured.
Many internet facing addresses/ports will not respond to any ping requests etc, or acknowledge there existence. If they did ack, that is just advertising to potential hackers that there is 'something' there.
For example, Visit http://www.grc.com/
] follow the links to ShieldsUp and put your internet ip in.