How to determine what process is listening on OSX

Question

Trying to help configure Laravel Valet on a Mac running El Capitan, and the user had installed MAMP previously. MAMP is disabled but anytime we load a valet address (mysite.dev) we get a standard Apache 404 page.

Is there a way to determine what process is listening on port 80 and conflicting with Valet so I can disable it?

Answer 1

See Who is listening on a given TCP port on Mac OS X?

lsof -n -i4TCP:80 | grep LISTEN

Or some such.