Bonjour Sync: waking up connection to 'server'


Bonjour sync has worked without any problems for me since it was first introduced sometime in the 13th Century. For some reason, since Big Sur, I’ve encountered the following problem, which may or may not be related to DT3 — but as DT3 is the only program it affects, I thought I’d ask here to see if anyone can shed any light on it.


  • ‘Server’ DT3 databases on the iMac
  • ‘Client’ DT3 database on the laptop
  • Both on the latest DT3 and Big Sur versions
  • I occasionally get the same problem connecting from an iPad
  • all the devices are on the same wireless network, with the same router/gateway and I’ve disabled ethernet so there’s no name clash.

This works flawlessly and has done for years, except…


On first opening, or after a period of lack of use, the laptop stops syncing with the desktop.

The solution is very simple: open up Screen Sharing from the laptop to the Desktop. I don’t even have to log on to the desktop — just opening the connection is enough to set the sync running again.

As soon as I do this, syncing recommences and it will continue happily until it doesn’t and I have to reconnect by clicking inside the Screen Sharing window.


  • The desktop is set to Wake on Network Activity
  • Connecting through Finder doesn’t seem to work (or not as reliably). Screen Sharing seems to be the only solid solution
  • Stealth mode is off on the desktop and DT3 is set to allow all incoming connections.
  • I don’t remember this being a problem with earlier MacOS versions

It feels like that the connection is lost when the desktop sleeps and it’s no longer accepting DT3 as a valid alarm clock.

Has anyone experienced this or has any ideas about how to investigate it?


This is not supported by Bonjour sync currently, therefore only the screen should sleep.

Thanks Christian, but could you please explain how that affects this problem?

Depending on your system settings the desktop might actually sleep and therefore the notebook can’t synchronize.

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I can’t put my finger on it, but I find that Big Sur (and Catalina before that) seemed to have “trouble” occasionally with recognising previously recognised network shares on other devices (NAS and my wife’s MacBook, for example) and other services when coming out of sleep.

Not all the time and I have found no way to reliably reproduce it. I’ve not sought guidance from Apple Care as most likely they will blame the NAS or other, or suggest reinstalling the OS and i don’t think either are useful. When I want to ensure sleep doesn’t get in the way I run Amphetamine to stop sleep. Otherwise I just live with it. Sometimes I just have to re-boot to clear it. Not useful to you, but I sympathise…

I posted the problem on MPUG forum and eventually I got some good advice about tweaking a setting on my network switch. I had a dumb switch so replaced with a newer model “smart” switch and it has helped. But still occasionally experience the “outa sleep” issue. While I didn’t notice it, it might also be affecting Bonjour as it’s also a network service.

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It’s set for the Hard Disks to sleep whenever possible (but it’s been set like that for years).

The odd thing is that connecting through Finder ‘Connect As’ (which presumably doesn’t use Bonjour) doesn’t always trigger the sync.

I wouldn’t be surprised if it is Big Sur and I’ll follow up your post.