Screen Sharing doesn't work with the Firewall turned on.

Question

Marianco1 Author

Level 2

243 points

Screen Sharing doesn't work with the Firewall turned on.

I updated one of my Macs (MBP 13-Inch 2012) with Yosemite.

Unlike my other Macs, I cannot access via screen sharing this Mac if the Firewall Turned ON.

1. screen sharing

2. Remote Desktop

3. Screens

4. iTeleport

5. VPN

I can access its hard drive and copy files. I just can't see its screen. I get an error message that the connection could not be established.

This is despite Screen Sharing being explicitly allowed when the Firewall is turned ON.

So I have to turn the Firewall OFF to remotely access this Mac, leaving it in a vulnerable position.

Any ideas?

I restarted.

I updated Remote Desktop

I Reset the Parameter RAM.

Any ideas?

Thanks.

MacBook Pros, Other OS, Mac OS X 1.6.x

Posted on Feb 1, 2015 9:37 PM

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Answer 1

mario49

Community Specialist

Feb 4, 2015 8:35 AM in response to Marianco1

Hey Marianco1,

Thanks for the question. If I understand correctly, you are not able to share computer screens. It looks like you have already done some troubleshooting. I would recommend that you read this article, it may be able to help the issue.

OS X Yosemite: If you can’t share computer screens

Thanks for using Apple Support Communities.

Have a good one,

Mario

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Answer 2

Sep 24, 2015 8:40 PM in response to mario49

Mario49, I have the same problem as the original submitter, and the article you linked is nice, has all the basics, but it offered no new information for me.

On the same Wi-Fi network, trying to screen share from my MBP to my wife's iMac (both on Mac OS X 10.10.5). On the iMac Screen Sharing is permitted for "All users." If I turn off the firewall on the iMac, I can get it. Turning on the firewall prevents the connection ("Connection failed. Make sure that....").

I've already removed all the user-modifiable applications from the list (under "Firewall Options...") so that only File Sharing (AFB, SMB), Remote Login (SSH), and Screen Sharing are listed (green dots). Nothing else is permitted or forbidden. I've also checked the box to allow signed software.

Nothing short of turning the firewall off completely lets me into that iMac. Something is wrong, but I'm at a loss to be able to identify it.

Any suggestions would be welcome.

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Answer 3

Sep 26, 2015 12:42 PM in response to Steve Davidson

After doing what I described above, I disabled and reinvoked Screen Sharing. The I rebooted and logging back in, and was presented with a dialog that asked if I want to allow sharingd to accept incoming connections. And subsequent to that, it worked. Not sure why the previous allowance didn't work, but at least now it does.

Case closed (for me, anyway).

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