Firewall locked you out of screensharing on OS X?

Sadly, I had this experience lately. Even though I had the firewall explicitly set to allow connections using Screen Sharing, for some reason my Mavericks OS X 10.9 server hiccuped and I couldn’t access it via screen sharing.

Here’s how I resolved my dilemma:

I was thankfully able connect via SSH; so I first checked to be sure the screensharing daemon was running:

It was. So, next I looked at the firewall log to see if it was blocking. Sure enough, it was:

Boom, there it is. The firewall’s blocking screensharingd.

Next, I checked my firewall settings:

Oddly, there was no entry for screensharingd…

So, I added it:

I then checked firewall settings again, and saw that it was added and was set to allow incoming connections:

If it were instead set to disallow incoming connections, I would have ran:

Then, I restarted the firewall, noting these important caveats: You need to sudo the unload & load of the daemon (/System/Library/LaunchDaemons/com.apple.alf.agent.plist); otherwise it’ll try to unload & load them from the user launchd, which won’t work right. Do not, however, sudo the commands for the useragent:

Had I wanted to simply disable the firewall, I would have first issue the following command, and then restarted the services:

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