lsof can list all open files in osx. As directories, sockets are all also files in unix. lsof can also be used to find open ports/sockets/directories:

• To list all open TCP sockets with port numbers:

  sudo lsof -i -P

• To find processes open a folder or any file in that folder

  sudo lsof +D /the/foler

• To find process open any file on a dev

  sudo lsof /dev/disk0s2

• To print all found process id only

  sudo lsof -t <other commands>

Details can be looked up in the man page.