Shodan is used by blackhats and whitehats to quickly find open ports and other fingerprints of IP's and servers. https://www.shodan.io/
Check local machine for open ports:
netstat -aon
If you want to show the process name in the list, add b so netstat -aonb. Not that this makes it quite slow.
This site is meant to be used as a reference for myself, although others may find it useful. I use it to keep track of certain fixes, software, and other solutions which I may need while assisting customers. The page layout is pure HTML/CSS and is kept simple to optimize loading time and fast results.