Haven't look at that code for a while, but IIRC it does a simple HTTP request then checks the returned HTML for anything that looks like a v4 literal, eg. http:

Haven't look at that code for a while, but IIRC it does a simple HTTP request then checks the returned HTML for anything that looks like a v4 literal, eg. http://174.136.109.18 http://174.136.109.18.