Any Android CalDav/CardDav servers out there for syncthing?

Does anyone know of a CalDav/CardDav server you can run locally on Android and output a database/file structure that syncthing can pick up? Something like Fennel which is written in Golang or kcaldav in C but wrapped up as an Android apk?

I’ve read the NextCloud users run DAVdroid to bridge between Android’s Contacts and Calendar to remote server they host or rent (cloud)… So it hit, why not just put in “localhost” in the url instead and run it on the phone/tablet itself? I mean, you don’t need a full fledged web server and encryption if it’s local. You barely need password verification… No?

Am I on to something here?

Also found carldav and davserver coded in Java. Must be something out there for Android…

And we have a winner: DecSync


On the one hand it’s an interesting idea, syncing the actual calendar and contact data as files between devices and then running the CalDAV and CardDAV service locally.

On the other hand it’s quite absurd to sync key-value mappings to a file system, which then is synced to another device, just to be synced to a database again, with a backend which then serves the data to a calendar/addressbook client - when CalDAV/CardDav is just a protocol to access ics/vcf files anyway.

Just for completeness the Android app for DecSync is DecSyncCC which can be installed from F-Droid: DecSyncCC on F-Droid

You might also be interested in EteSync which tries to replace CalDAV/CardDAV with something encrypted.