I was able to reproduce the problem. As soon as DAVdroid tries to download the contacts with REPORT addressbook-multiget, the server returns “500 Internal Server Error”.
addressbook-multiget is mandatory for CardDAV servers and required for fast contact synchronization.
Can you please report this problem to the server vendor and provide some reference (for instance, a link to the bug report) here?
What about giving Internet access to your device and using a firewall to restrict traffic?
My local network is entirely airgapped with no external internet access, and that’s the way it has to be. My tablet is never going to touch the internet, and neither are any of the computers on my local network.
DAVx⁵ is designed for the Android sync framework, which requires an Internet connection. Synchronizing without ever having Internet access is a special requirement, which is covered by the design goal of DAVx⁵ .
So people who don’t have access to the wider internet are “special requirements”? This is mildly infuriating. Why the hell do so many developers design their apps to simply NOT WORK if you have a device that never touches the internet? There are a shit ton of people in the world who have devices that cant connect to the internet!
In particular its annoying because you guys made the design decision to build an app for CalDAV, which does not require access to the internet, and you ADDED ON A REQUIREMENT FOR AN INTERNET CONNECTION!
And your app is the only option availible on f-droid too. Now i need to start shoping around for open source apps availible on the play store, which is a massive pain in the butt.
By the way, this does not only affect DAVx5, but all apps which use the sync framework, including the Android email app, Firefox (Firefox Sync uses the sync framework), messengers (contact lists are synced over the sync framework) and probably much more.
Of course firefox and email and messengers dont work when you dont have internet, those are all apps that at their core involve communication with other people in one form or another, which is what the internet is for.
But thats not what calendars are for. Calandars are just a way of keeping track of events, no communication with other people nessisary. Saying I cant sync my calander without an internet connection is like saying I cant sync tasks or notes to self or text files without a connection to the internet. Its entirly ignoring a big part of what people use calanders for.