[ultrablue]

curllib will tell you whether there's something there, presuming the network is available.

In fact, a simple HEAD request will suffice for that.

That would also prove that the domain is registered, presuming DNS is working.

[icebraining]

That's not enough; some registrars keep a domain parked and responding after the registration has expired.

[lookingfj]

And this is exactly the problem I want to solve and the key challenge