How to get local IP address

Some time ago I was need to detect local IP address of the machine where my Firefox add-on is installed. I've not found complete example. Finally, I've found the next solution:

var dnsService = Components.classes["@mozilla.org/network/dns-service;1"].
getService(Components.interfaces.nsIDNSService);
var ip = dnsService.resolve(dnsService.myHostName, false).getNextAddrAsString();

Nothing difficult!