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Unreliable screen sharing connection to headless MacMini M1 Big Sur

Well not exactly headless. I installed my MacMini in my entertainment center and use it for playing music. The HDMI output is connected to a 50" LG TV, but I don't like to have the TV on all the time, so I mainly like to connect to the mini via Screen Sharing from a MacBook Pro (Catalina) in the same room. The screen sharing connection works most of the time, but eventually disconnects. Sometimes it only works for an hour or so, sometimes for a day or two, but at some point the screen sharing display will show a spinning wheel and "Reconnecting". Once that happens it never reconnects. If I quit Screen sharing and try to connect again, it times out without connecting. The only way I can get it to reconnect is to SSH into the Mini and run `sudo killall screensharingd`, then I'm able to connect again.


In the Energy Saver Preference pane on the MacMini, I have it set to never turn the display off (but I do have a ScreenSaver that comes on after half an hour). On the MacBookPro the display will go to sleep after about 2 hours (no screensaver), but I have `Prevent computer from sleeping automatically when display is off` checked.


I've currently have "Remote Management" enabled on the Mini. I was using "Screen Sharing" at first. They seem to work the same way and have the same problem. I'm not sure what the difference is-- they both seem to be basically VNC.


Both machines are connected to the same network with ethernet.


Is this a known problem with the M1 MacMini? Or screen sharing in general?



Mac mini, 11.0

Posted on Dec 10, 2020 2:42 PM

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Posted on Dec 23, 2020 11:53 AM

This seems to have fixed itself. I rebooted the server to try to define the problem better. First, I decided I should make sure the TV was turned on when first connecting via Screen Sharing. That worked and the session stayed up for over 3 days. Then I tried to break it. Experimenting with connecting and disconnecting under various conditions, I could get it to fail only once, when it popped up a message saying the server and client were incompatible. I can't remember what I did just before that, but since I was intentionally "abusing the relationship", I feel that's an acceptable outcome.


Embarrassing to think that I may have fixed this with a simple reboot.

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13 replies
Question marked as Top-ranking reply

Dec 23, 2020 11:53 AM in response to Chester Wood

This seems to have fixed itself. I rebooted the server to try to define the problem better. First, I decided I should make sure the TV was turned on when first connecting via Screen Sharing. That worked and the session stayed up for over 3 days. Then I tried to break it. Experimenting with connecting and disconnecting under various conditions, I could get it to fail only once, when it popped up a message saying the server and client were incompatible. I can't remember what I did just before that, but since I was intentionally "abusing the relationship", I feel that's an acceptable outcome.


Embarrassing to think that I may have fixed this with a simple reboot.

Jan 26, 2021 5:51 PM in response to Chester Wood

My previous reply indication that the issue was solved turns out to be incorrect. The problem returned repeatedly, sometimes just after rebooting. The screen sharing session will fail sometimes within a couple of seconds, sometimes a couple of days.


An Apple senior advisor has assured me that this is a known problem the the M1 graphics driver and a fix should be coming in the next OS release.

Apr 1, 2021 1:33 PM in response to Chester Wood

I have what may be a related issue—at least it's similar. I have a 2014 Mini headless but connected to HDTV (it's my media server for PLEX.) I often screen share into the Mini from my MBP on same network. the Mini never sleeps and I rarely have the HDTV on and connected to the Mini (I use an apple TV for all media watching.)


Anyway, until Big Sur I was able to easily screen share into the mIni using "share screen" from the finder or Apple Remote Desktop. After Big Sur, if I do not access the Mini for a few days ScreenSharing & ARD time out when attempting to connect. I can get in using Team Viewer and after doing that, ARD or ScreenSharing work again for a period of time. But after a day or two they time out again.


I too have tried enabling Remote Management and Screen Sharing—behavior is identical with both. I can SSH into the machine but something has happened with screen sharing since Big Sur.


I'd be curious to know if you ever resolve your issue and I plan to try SSH and killing screen sharing as you suggested...sounds like you may be on to something.

Apr 2, 2021 1:57 PM in response to Philip Chadwick1

I suspect Apple made an incompatible change in Screen Sharing in Big Sur. Since I was occasionally getting a message saying the client and server were incompatible, I finally bit the bullet and upgraded my client MBP from Catalina to Big Sur. It's only been a couple of days, but I think it's working better so far. I also upgraded my iMac from Mojave to Big Sur.


On Mojave I was having a different problem: instead of disconnecting frequently, the client would stop sending all the keys to the server. For example, CMD-SPACE would stop invoking Launchbar on the Mini and would invoke it on the iMac instead. So far since upgrading the iMac that problem has gone away.


I am still getting occasional disconnects, but I am also stressing things a bit more by sharing the screen from both clients at once. That was not possible before-- the second client just wouldn't connect.


Oddly, the iMac often fails overnight complaining about authentication while the MBP stays connected. And I authenticate from both machines the same way.

Apr 11, 2021 8:33 AM in response to Chester Wood

My screen sharing works intermittently. Big Sur, v11.2, late 2020 Mac Mini M1. Seems to go out overnight. Works fairly reliably during the day. Come back the next morning to try and open a screen, can't connect. Can share files though. Additionally, once connected, I can cut and paste (back and forth) for a while, but then that stops working. And, there are control keys and other key sequences accepted for a while, but then that stops working. For example, I use emacs from the terminal and it stops working after a while. I really need this. I hope it gets fixed soon.

Apr 11, 2021 1:37 PM in response to sumarc

Things have improved since I updated my clients to Big Sur, but I'm still having problems that I'm beginning to think are due to limitations of the graphics hardware on the clients. Lower resolutions work better than higher. I use SwitchResX to set the same resolution on both sides so I can take advantage of the maximum resolution of the monitor without scaling. On my 2017 iMac with Radeon Pro 580 8 GB graphics, when using the native resolution of 2560x1440, it works pretty well most of the time, doesn't disconnect permanently, but sometimes has a noticeable lag (all machines are connected by gigabit ethernet) and a couple of times the connection stops and the "Reconnecting..." screen displays for a minute or so, then comes back. But with 2048x1152 resolution (thankfully my preferred setting) it works perfectly and stays up for days.


My late 2013 MacBook Pro has Intel Iris 1536 MB graphics and I use an external Apple Cinema Display for screen sharing (1680x1050 native resolution). When set to that resolution (1680x945 on the Mini) things are pretty much as bad as before. It can disconnect permanently and I have to kill screensharingd on the Mini while actively using it after an hour or two. But 1280x800 (1280x720 on the Mini) resolution seems to work much better. I haven't had time to see how long it stays up at that resolution yet because it's not very useful for my current project--- I need to use the higher res of the iMac. 


Also since my last post I have stopped trying to screen share from both clients at once. There wouldn't be much point since given what I've discovered I would have to run at 1280x720 on both clients.

Apr 29, 2021 1:58 PM in response to Chester Wood

It does appear that the performance of the client hardware is the key here. I turned off encryption by executing


defaults write com.apple.ScreenSharing encryptRFBDataStream 0


on the server and both clients. This fixed the problem and finally I am able to reliably view screen sharing at full native resolution on the Apple Cinema display.


In hindsight, this is pretty obvious, but when I noticed the problem I'd just started using a machine with a new architecture and new OS, so I assumed the problem was there.


But OS compatibility is also part of the problem. To verify, I tried booting my MBP off a Catalina SSD clone made just before I upgraded it to Big Sur. I turned off RFB encryption and experimented with that for several days, and basically had the same results as before--- frequent disconnects at either resolution.


So is this the place to complain about Apple's consistent disregard for backwards compatibility? I mean, this is VNC, for heavens sake, an ancient protocol. Any client should be able to connect, even an old Windows machine. Why should it only work with exactly the same version of MacOS? I suppose, to give them the benefit of the doubt, that they could have come up with a more efficient transfer protocol in Big Sur, which of course would have to be negotiated and present on both sides, which could add just enough efficiency to overcome the deficiency of the older hardware.


It would be interesting to know if that's the case.

Jun 6, 2021 5:12 AM in response to Chester Wood

I think I might be having as similar issue, so am looking for advice. I'm running a 2020 MacBook Pro (Intel chip) with Big Sur 11.3.1, and I'm using Screen Sharing to view my MacMini 2014 Big Big Sur 11.3.1. Similar to the member above, I use the Mac Min for media, so its connected via hdmi to a Sony tv, and often I view the Mac mini on the MBPro via Screen Sharing with the tv off (actually on stand-by).


The issue started after installing Big Sur. When I view the MacMini screen via Screen Sharing a message pops up from the Screen Sharing icon in the menu bar over and over again on the MMini saying "Your screen is being observed". It then does an abrupt sort of flicker and I find the connnection has been lost for a second or so. It wouldn't be so bad, but it seriously disrupts what ever I'm working on such as moving/copying files, general maintenance, or choosing songs etc on Music.


Both machines are connected via normal wifi ie not a private local wifi, such that I can use internet on the MMini if I need to. I wondered if my wifi was up to the task of connecting two machines running Big Sur. But there seem to be so may other little changes in Big Sur (eg my Automation scripts no longer work), that it maybe some residual setting left over from previous OS (Catalina), addressing the backward compatibility issue raised above? Any help appreciated. Thanks.


Jul 5, 2021 12:44 PM in response to peb2021

Have you tried a lower screen resolution on the Mini? If you are driving the TV with full 4K res, for example, the mini could be struggling to provide another 4K stream to screensharing. Also, the wifi could be a problem, depending on your router and your wifi configuration options, and competition with other services using wifi. That wasn't an issue in my case, cause everything's connected with gig ethernet.


Good luck!

Unreliable screen sharing connection to headless MacMini M1 Big Sur

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