February 20, 2008 at 10:21 PM by Dr. Drang
In two recent posts, I discussed my (so far limited) experiences with the new screen sharing feature in Leopard. I’ve done a little more experimenting and have some new information.
Forwarding port 5900
In the first post, I described how I did screen sharing over the internet through an SSH tunnel. Near the end of the post, I mentioned that an SSH tunnel may not be necessary if you configure your router to forward port 5900 to the computer you want to control. I can now confirm that this works. Yesterday, I opened port 5900 on my office router and forwarded it to port 5900 on my iMac. When I got home, I fired up my iBook and did a Connect to Server… from my iBook. The Screen Sharing application launched and I was soon looking at a scaled version of my iMac screen.
I’ve since turned off the forwarding of port 5900 because:
- The non-tunnel connection didn’t seem any faster than going through the SSH tunnel.
- I don’t like opening up any more ports to the outside world than is absolutely necessary.
- I just trust SSH more than I trust the security setting of the Screen Sharing application. This may be unfounded—Screen Sharing could be using SSH, for all I know. But since I don’t know what Screen Sharing is doing and I do know what SSH is doing, I’ll stick with SSH.
In my first screen sharing post, I mentioned that when Screen Sharing first launches with a scaled remote screen, the window showing the remote screen doesn’t update when you click or type. Resizing that window just a bit or toggling to the unscaled view and back “wakes up” the window, and it will update just fine from that point on.
In my second screen sharing post, I described a much weirder behavior in which pressing the tab key while using the Screen Sharing application causes the remote computer’s application switcher to appear, as if you had pressed Command-Tab.
Even weirder, the remote computer then behaves as if the Command key were pressed until you press a modifier key—Command, Option, Control, Shift, or Caps Lock.
I wondered if these two bugs were somehow related to my use of the SSH tunnel (at that point, I had run Screen Sharing only through a tunnel), so I tested them out last night while I was connected directly through port 5900. Same behavior; the bugs are unrelated to SSH tunneling.
Sharing through iChat
I tried to get screen sharing working through iChat but was unsuccessful. I was at work, my wife was at home, and we tried to establish a screen sharing connection through an AIM chat. No dice. The error message is the very helpful
Failed to start Screen Sharing because: Screen sharing could not be established.
The iChat help doesn’t say anything about router configuration, and it does say you can screen share over AIM, so I suspect the problem is an AIM issue. We’ve had only spotty success in doing video chats with each other and with our daughter at college, which I also attribute to “issues” with AIM.
Local network screen sharing
Screen sharing my wife’s iMac from my iBook G4 within our home network was a snap. Interestingly, the “nonresponsive window” bug didn’t appear; mouse clicks and keystrokes in the Screen Sharing window got immediate responses with no need for the window resize or scaling toggle tricks outlined above.
The Tab key bug, on the other hand, was the same as when I screen shared over the internet. I’ve filed a bug report with Apple.