If you want to connect in from the internet you need to know the IP of your server, or of the router. If you have ddns setup, I'd have thought you would be able to find that out by DNS assuming you know the domain name that you are using. You would also need to have a route opened up through the various firewalls along the way - they would probably not be opened up by default and you should think twice about opening them since your system will then be open to attack.