Occasionally you may find yourself in a situation where you are seeking to find what open TCP connections are in a listening state on a Mac. This can be useful whether you’re troubleshooting particular network issues, or simply looking to identify which processes are listening on specific ports on a Mac.

We’ll be using the command line lsof tool to find out what/who is listening on open TCP connections on a Mac, making this most appropriate for advanced Mac users who are comfortable with the Terminal and sudo.

How to Find What Listens on TCP Ports on…