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Solve Snow Leopard's Screen Sharing Bug

[Update: This bug appears to be fixed in 10.6.1 on some systems. In my tests, I no longer get the black screen error described below on one computer; on another, the problem remains.]

I'm addicted to remote access to my Macs. I have LogMeIn and Timbuktu Pro installed on most of the several computers I own or manage, in addition to using Leopard and now Snow Leopard remote access.

But Snow Leopard has thrown a spanner in the works. The first time I connected using built-in screen sharing, the remote screen was black (see this demonstration screencast I made). I assumed I'd made an error, and tried other methods to no avail. I switched to LogMeIn, and the remote system was fine.

After some experimentation, I discovered the bug appears to be in Snow Leopard in the Screen Sharing application that handles connections via Bonjour, Back to My Mac (which uses Bonjour), and directly entered addresses. (The Screen Sharing program is hidden in /System/Library/CoreServices.)

The solution is tedious but works every time I've tried it. The View menu shows Full Quality (no lossy screen compression) or Adaptive Quality (lossy but faster display). Choosing either whichever quality option is not selected or - bizarrely - the currently selected view option, and the remote screen starts streaming.

Apple needs to fix this bug, which has occurred on every system I've updated to Snow Leopard, although I haven't heard vociferous complaints. Apple's support forums have reports from other puzzled and irritated users. There's no way to know how widely used remote screen sharing is. (Commenters on this article are divided: some aren't seeing the problem; others are on one or more of their computers.)

To initiate a screen sharing session in Leopard or Snow Leopard, you use the Sharing section of the Finder sidebar, selecting a server and then clicking the Share Screen button in the upper right of the Finder window. That button appears only if the Bonjour or Back to My Mac system has Screen Sharing enabled in the Sharing system preference pane. You can also launch the Screen Sharing program and enter an IP address, Bonjour name, or hostname.

Some portion of the Screen Sharing program's underlying framework is also used for screen sharing via iChat, but it's sufficiently different to avoid this problem.

I'm currently revising my book, Take Control of Screen Sharing in Leopard, to cover changes in Snow Leopard, and add details about screen sharing via Skype and using iPhone applications. If you have screen sharing questions or tips, please send them my way.


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Comments about Solve Snow Leopard's Screen Sharing Bug
(Comments are closed.)

David McNamara  2009-09-07 14:22
I too use Screen Sharing a great deal, but have had no problems sharing back and forth between 2 Snow Leopard and 1 Leopard machines. Seems like it may be a conflict with something else you have on those machines.
aresee  2009-09-07 14:29
I hate to be in the "That's not happening to me" crowd. But I do not have this problem. I am using an original MacBook Air updated to 10.6 to connect to a 20" iMac running 10.5.7. This has always worked with no problem both locally on my LNA and over the internet, 300 miles away.
Glenn Fleishman  2009-09-07 17:05
As I note, others are seeing this problem and talking about it in the Apple support forums. As far as I know, none of the four machines I've tested among share nearly anything in common. One is stock Snow Leopard machine on loan from Apple.
Craig Morgan  2009-09-07 17:27
I'm with David above ... very heavy user, my MBP on SL, 3 target systems on SL and 1 target on Leopard (PPC) and none of them exhibit the issue.

For the last 6 months or so I've been alternating with using JollysFastVNC to the same systems as its somewhat faster and more reliable making initial connection, might be worth a try as its free and very functional these days.

SS has been a great boon, a little slow to mature but now in 10.6 hopefully the MobileMe integration will settle down and it will be a nice stable feature.
Gerhard Giedrojc  2009-09-07 18:17
I have this problem when connecting from my Macbook Pro to my desktop pro machine, black frozen screen. However there is no problem when I connect the other way around, from the desktop to the laptop. It works fine this way. Strange little bug.
Glenn Fleishman  2009-09-07 18:37
Both running Snow Leopard? Hm. I wonder if enabling VNC compatibility is the problem. Nope: Just went and checked, and was unable to remove the black screen.
C. Hussussian  2009-09-07 18:43
I have been having this exact same problem and agree that it is an issue with Snow Leopard. Sharing that has been without any problems for a year was broken under 10.6. Exactly as you describe: black screen initially, red screen with changing to "full" quality, normal screen with changing back to "adaptive". Thankfully this workaround continues to work for now. Hopefully this will be fixed in the next updat.
Hmmm...I have a Macbook running Snow Leopard.
I can Screen Share to both an iMac running Snow Leopard, and a PPC Mac Mini still running Leopard

Pete B  2009-09-07 19:04
I'm having this issue on a Macbook Pro connecting to a Mac mini. Both running Snow Leopard.
Darren  2009-09-07 20:08
Two laptops running Snow Leopard: MBP and white MB - the MBP has the black screen (which is killing me as I use it to admin a Mini) but the MB does not. No ideas why. At least your semi-fix has saved me from jumping out of window.
I suppose this is happening over wifi for most people but it's worth noting that similar black screens used to occur when jumbo frames were enabled on gigabit enabled machines on Leopard. I don't recall whether toggling the quality setting helped with that scenario but perhaps this new issue is network related.
Jeff Greenberg  2009-09-08 05:25
Have you tried this with the system forced at 32 bits? By any chance is the app @64 now?
John VanDyk  2009-09-08 10:51
I have not experienced this, but did experience Screen Sharing repeatedly asking me for a password and erroneously claiming that it's failing. After some investigation, it turned out that if I had a valid kerberos ticket for Mail, screen sharing would do that. Typing kdestroy at the command line allowed me to connect to screen sharing clients (Leopard and Snow Leopard) as normal. If I get the screen sharing connection up first, then I can get a kerberos ticket for Mail and the connection stays up.
I haven't seen this at all and I have multiple Snow Leopard machines and Multiple Leopard machines and screen share freely in either direction from all of them. Are you setting the screen sharing prefs through "Screen Sharing" under the Sharing Pref Pane or Remote Management in the Sharing Pref Pane? Mine are both set in Remote Management.
Glenn Fleishman  2009-09-08 16:16
For me, always in the Screen Sharing service. However, this affects the client machine for me: a Snow Leopard system accessing a Leopard computer gets the same black screen for me on four different computers, one of which is a stock Mac with Snow Leopard's release version being the only version ever installed.
Richard Sampson  2009-09-09 05:18
I am not seeing this problem on a Mac Pro or MacBook Pro. Both with SL installed.
David S.  2009-09-09 14:37
Screen Sharing is working fine between my two SL Macs (a 15" MBP and a 24" iMac). I do, very briefly, get a black window when I connect to the remote machine but in less than a second up comes the remote desktop or screensaver and all works normally. I'm using Adaptive Quality setting.

Something is obviously different in people's environments, but what it is I've no idea. Hmm, routers/networking perhaps? I'm using an Apple AP Extreme (11g) basestation, maybe it only affects 11n routers/networks? Does anyone get this problem over an Ethernet n/w I wonder?
I have 4 Macs on my AP Extreme 11n network (Mac Pro, Macbook Pro Unibody, Macbook Pro, Mac Mini) all of which are wireless except the Mac Pro. All of them are able to share their screen with the exception of the Mac Mini. The work-around stated earlier works however. I haven't been able to determine what's different with the Mac Mini.
Kevin Simmons  2009-09-10 07:16
I'm not having this problem; however snow leopard screen sharing forbids me from saving the parameters from previous sessions. I have to enter the ip address or name every time i initiate a session.
Glenn Fleishman  2009-09-10 15:00
It looks like 10.6.1 solves this problem. I just tested four remote systems; on a couple, just a brief flash of black, then the remote screen, while the other two brought up the remote screen instantly.

Other fellow sufferers?
After a few iterations, it seems the problem (for me) is that the black screen only appears when the resolution is set to full screen and the shared machine is set for a higher resolution than the one I'm using.
Even after updating to 10.6.1, I see the same behavior Bill reports. If you set view to scaled, the display works correctly. If you set full size, then you have to toggle the quality to get the display to appear when the remote screen is too big to display in full.
Glenn Fleishman  2009-09-13 20:34
Fascinating. Toggling full/shrunken screen mode does nothing for me. Strange how this is manifesting in different ways on different people's Snow Leopard installations.
Looking at this again, I found that the problem was that I had Scaling turned on - when I turned it off it worked as before ....
Just Me  2009-09-12 16:13
You fail to mention (what I find to be the most convenient) another way to open screen sharing. That is to use Go To Server ( cmd K) and enter a URL of the form vnc:// or with the IP address vnc://a.b.c.d. You also have the ability to add routinely used URLs to the list.
Glenn Fleishman  2009-09-12 16:18
That's what you find the most convenient way? That's rather cumbersome and requires dynamic DNS or static IPs/hosts.
Jeremy  2009-09-16 11:21
You can use bonjour names with this approach.

So, vnc//:MyServer.local

Of course, that doesn't apply if you're not on the same network. I really miss the ability to reconfigure the Screen Sharing app to have a bonjour browser.
cfailor  2009-09-17 10:01
I too am having connection problems, new Snow Leo on MB, and connecting to Leo on a mac mini.
runs ok for a minute then slows and or just stops responding. the new 10.6.1 update did not help.
Peter Gerlings  2009-09-19 00:52
I'm glad it's not just me!!

I have a mac mini that acts as a disk server, and I cannot access it for more than a few seconds before it freezes. Sometimes I get the blank screen, other times it does open an initially working screen sharing window, but it lasts for two seconds, tops.

Unfortunately, I just tried your suggestion to change between full and adaptive quality, it doesn't help.

At least I know it's a known issue, and not just me. I don't need to access this machine very often, so I hope that 10.6.2 comes out soon and fixes the problem.

Don Conley  2009-09-19 10:26
It's great to see so many comments about screen sharing! I screen share with Jaadu on my iphone remotely with wifi and 3g.
I am starting to believe that the "revolutionary" in Apples tablet is going to be "screen sharing". The tablet won't need to be smarter than an iphone. It needs to be bigger. Leave out the hard drive and fast processor both of which add to cost and produce heat. Set up the hardware to push a lot of pixels.
Slingbox can get enough pixels and sound to run good video on the iphone. Slingbox is the best comparison. You can't bring your home TV with DVR, cable and recorded programs so you screen share. Now, why have another computer if you don't have to.
There are problems maintaining multiple computers. Sync! cost, upgrades, ram and storage memory, application installation to name a few, and did I mention Sync?
With one computer you will have less maintenance time.
Sorry for redirecting the conversation but I wanted an opinion from someone on the cutting edge.
Don Conley  2009-09-23 16:35
Found a similar problem with a resolution;
"I think that it is safe to say that they updated the Screen Sharing app in Snow Leopard and the version that i had copied and moved to my applications folder was the old leopard version.

When i copied the version from the core services folder into my applications folder it worked like a charm."
piprog  2009-09-27 12:14
Hi Folks,

One question from a MacNewbie: how can I do Screen Sharing in a dual monitor setup, for only one of the screens on Snow Leopard?
Jeff Carlson  An apple icon for a TidBITS Staffer 2009-09-27 12:33
When you're in a screen sharing session and the other, shared, screen has multiple monitors, you'll see a pop-up menu in the upper-left corner of the window that lets you choose which screen to display.
piprog  2009-09-27 16:08
Thanks Jeff for the quick reply!

My "server" is the standard Screen Sharing (VNC) server on Snow Leopard, but the client is a VNC client (TightVNC 1.3) on WinXP.

I suppose your suggestion works with a Mac client? I don't seem to see the popup in TightVNC. Any suggestions?

Jeff Carlson  An apple icon for a TidBITS Staffer 2009-09-27 16:34
Yes, the control I mentioned appears on a Mac-to-Mac connection. I haven't tried mixing environments, so hopefully someone else reading this can chime in with their experience.
Glenn Fleishman  2009-09-27 19:31
The Screen Sharing software is a superset of VNC with some differences, so it's possible that TightVNC won't be able to access that mode. In fact, I don't know what the standards are in VNC (if any) for multiple-monitor access selection. That may be an Apple proprietary extension that's beyond the VNC compatibility mode you enabled.
piprog  2009-09-28 02:56
Thanks Gentlemen!
Planeten Paultje  2009-09-30 01:13
Two macs here and both show the "Black Screen Bug". I just found out that the root user doesn't have this problem; Screen Sharing works as it should.
Ed Howe  2009-10-01 08:25
I have the problem connecting from my MacBook Pro (SL) to my Desktop Pro (L) using Cmd-K. The desktop has dual monitors, so I discovered that by changing the view to a single monitor and back makes the screen visible.

Interestingly, after connecting a couple of times, I can no longer establish a connection and have to restart the desktop. It is a real pain.
Jimi Lee  2009-10-02 21:46
Thanks man, I was too having this issue and you suggestion worked for me too!
BlondoftheWoods  2009-10-03 12:30
I have a MB Pro, recently upgraded to Snow(job) Leopard. I used to be able to connect to my Dad's Mini (when we were both running 10.5) via iChat. Now I get "an unknown connection error has occurred." I NEED this screen sharing ability back to manage his computer! Help!
johnnyduke  2009-10-07 20:41
that's the ticket! switching quality in "when display remote screen:" in Screen Sharing preferences made the flashing black screen revert to proper screen sharing. Thanks for the solution.