UPnP support in the router allows applications such as NetSnap to automatically open and close mappings from the public IP address to the internal IP address and port of the application.
In order to view images, pages, and streams from the Internet. NetSnap must be reachable on the public IP address. If uPnP support is disabled, and no manually configured mappings on the router exist, then NetSnap may not be reachable on the public side of your Internet connection.
Not all routers support uPnP or have uPnP disabled by default. Check the support documentation of your router on how to enable uPnP. Alternatively configure your router to manually add port mapping to your NetSnap server internal IP address.