Querying for Ethereum nodes (like how ethernodes.org does it)

Hi all,

I'm wondering how https://ethernodes.org/nodes works on the backend -- did they just have a script using devp2p discovery.py or otherwise to pull this data?

For example, is there an example of getting such node stats such as total # nodes on the network, getting a list of them, getting client diversity info from them and so on?

Appreciate your insight Ethereum-ites!