Non-server side method of getting local IP address in browser?

ip-address

Solution

Thankfully to Webrtc it is possible to access local IP from javascript.

Take a look at: http://net.ipcalf.com/ (source)

( It works in chrome )

However accessing local IP from Javascript could be a privacy and security issue.

and below simpler example then net.ipcalf.com

and on the jsfiddle

var RTCPeerConnection = window.webkitRTCPeerConnection || window.mozRTCPeerConnection;

var configuration = { "iceServers": [] };
var pc;
var localIP;

if(RTCPeerConnection){  

    pc = new RTCPeerConnection(configuration);
    pc.onicecandidate = function (evt) {  
        if (evt.candidate) { 
            if (!localIP) { 
                localIP = getIpFromString(  evt.candidate.candidate );
                console.log(localIP);
            }
        }
    };

     pc.createOffer(function (offerDesc) {;
        pc.setLocalDescription(offerDesc);                                      
    }, function (e) { console.warn("offer failed", e); });

    function getIpFromString(a)
    {
        var r = a.match(/\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/);
        return r[0];
    }

} else {
 //browser doesn't support webrtc   
}

Problem

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).

Original source