I am trying to provide a way for users on my LAN to "register" with the Network admin (me) without having to either a) host a page on my computer b) host a script on the central server (since it is only a router, not really a solid HTTP server) or c) sign up for a Dynamic Domain in order to either either of the first two and avoid the confusion of sending out a URL to a link to a local IP.
Is there a simple way to display the local IP address on screen via a client-side script? I'm thinking maybe I could have an iframe that points to some generic url with some javascript in the path, so that I can have the users go to a non-local site, and the iframe would pop up with their IP address that they can then enter into a form in the main remote page.
If all else fails, is there a way for them to look up their IP that is cross-platform and doesn't involve using the command line (I think the first, even if impossible, is probably more realistic than the second).