Have you set the virtual server (or, in some cases port forwarding) up, on your router, to make your IP-cam visible from the outside? It is shown in the documentation how this is set up in general.
D-Viewcam is viewable over the internet, but there again you need to set the virtual server (port forwarding) for the specific (live viewer, remote playback) ports, and activate the network service in D-ViewCam itself, before you are able to view it...