A tiny bit of googling says that vpnkit is used by docker. As an experiment, I shut off the docker beta on mac … then ofcourse the port becomes available again … Hurray … but now: No docker!
What to do? Can I tell vpnkit to use a different port?
I actually had the same problem on 17.09.0-ce-mac35 . (using port 80).
Your message prompted me to check for updates, but I was already up to date, so the next obvious step… Turn it off and turn it back on again. What do ya know?
Restarting docker fixed it. Thanks for posting this, probably saved me a ton of time.