I actually had the opposite problem with a mid-2011 MBP and an early 2009 Mac Mini. The Mini allowed screen sharing while the firewall was turned on (without having entries for screensharingd and kdc in the allowed list) but the MBP did NOT allow screen sharing while the firewall was turned on (with having entries for screensharingd and kdc in the allowed list). The solution for the problem in my case with the MBP turned out to be removing the entries for screensharingd and kdc from the allowed list, and screen sharing magically started working again.
But if you want to try adding them to the firewall, the trick is to navigate to the screensharingd and kdc executables in the Finder. Then in the Firewall Allowed list, click the Plus button to add a new entry, and either drag the screensharingd executable file from the Finder window into the file browser window for the firewall, or drag the folder proxy icon from the Finder window into the file browser window for the firewall and select the screensharingd executable. That should let you add an executable from within a package to the firewall allowed list. Then repeat for the kdc executable.
i'm not using my firewalls at all, and i have not been able to get screen sharing to work at all, which has never been a problem for me. i'm registered as an authorized user on both computers, the passwords are correct, but it keeps telling me that the username/passwords don't work. and this is after the computers have already been "connected" using the exact same passwords and user name.
Seems like you have the same or similar problem to the one I've described in another post:
Try connecting for screen sharing using the "Go/Connect to server" method in the finder menu. Use the format:
"vnc://(insert local ip here)"
This will request your login information but for some reason it will accept it and allow screensharing. At least it does in my case.
I had similar difficulty. Neither my Mini nor my MBP would share screens after the upgrade. I ensured Screen Sharing was enabled (in Sharing) and KDC, Screen Sharing and screensharingd all Allow Incoming Connections (in Security & Privacy -> Firewall).
That initially had no effect. Then I did two more things. I trashed the existing *.vncloc file on my MBP (~/Library/Application Support/Screen Sharing/*.vncloc) but not the *.vncloc on my Mini. Then I rebooted both systems.
On restart Screen Sharing worked fine on both systems. In my case it seems that it was a matter of updating the System Settings and rebooting. Even though I deleted the *.vncloc on the MBP I don't think that made any difference. That is because I didn't delete the original *.vncloc file on my Mini and everything still worked fine after updating System Settings and reboot.
Your mileage may vary. Good luck.
Opening port 5900 in my firewall settings worked for me.
5900 TCP Virtual Network Computing (VNC)
- vnc-server Apple Remote Desktop 2.0 or later (Observe/Control feature)
Screen Sharing (Mac OS X 10.5 or later)
My problem was that I could Screenshare from my iMac to my MacBook but not the other way round. I had been able to Screenshare in both directions before I upgraded both machines to 10.7.3
At the AppleStore I was able to Screenshare from the MacBook to another Mac so that ruled out a problem with the MacBook. The Genius advised me to turn the Firewall off on the iMac so I went home to do this. It didn't help. But...
I found the following did solve the problem.
On the iMac>System Preferences>Security & Privacy>Firewall
Leave Firewall On. I did not need to turn this off.
Unlock the pane if required then click Advanced
Then scroll down to
screensharingd (in my case this had a red dot and Block incoming connections)
Change Block to Allow. The red dot turns green
Relock the pane
Now Screensharing works in both directions
daveinabin has likely solved his problem by now, but since I just wasted a good many hours trying to solve the identical problem without any of the suggested solutions from my google searches helping, I thought I'd post my solution here, in case someone else runs into this problem.
Summary of the problem:
After upgrading the host machine to Lion, I could no longer screen share (didn't even get the login window) into it from other machines (running Lion or Snow Leopard) unless I turned its firewall off. Changing the 'allow incoming traffic' settings for screensharingd didn't change anything. The console showed that any screensharing attempts were being denied, even though the preferences pane was set to have it permitted.
Solution that worked for me:
1) Turned off all sharing in System Preferences.
2) Deleted everything (using the minus sign icon) in the Security -> Firewall -> Advanced panel (This may or may not be necessary; I tried this along the way and by itself it didn't help.)
2) Turned off firewall in System Preferences.
3) Trashed the following two files:
4) Rebooted the (host) computer.
5) Turned screen sharing back on in System Preferences.
6) Turned firewall on in System Preferences.
Now screen sharing works again as before.