Doesn’t let me sync to an intranet server due to requiring Internet for no reason

[navid-zamani]

Problem scope

• I'm sure that this is a DAVx⁵ problem.

App version

• I'm using the latest available DAVx⁵ version.

Android version and device/firmware type

Android 13 (Blackview BV8900 Pro (DokeOS 3.1))

Steps to reproduce

1. Install Radicale or any other CalDAV/CardDAV server on your PC.
2. Enable a WIFI access point on it. (E.g. via “network sharing”. In my case it is the standard Linux combo of hostapd and dnsmasq, that NetworkManager e.g. on Mint uses internally too. For the purposes of this bug, assume no firewall.)
3. Disconnect your PC from all networks but this AP. Especially from the Internet.
4. Let your DAV server host on that AP.
5. Connect your phone to that AP.
6. Use your phone’s browser to connect to your DAV server’s web interface. (E.g. to add an address book.)
7. Add a new account in DAVx⁵, and enter the details for your DAV server.
8. After it finished, sync DAVx⁵ manually.

Actual result

The browser connects to the DAV server perfectly fine.
DAVx⁵ also can set up the account perfectly fine and get all details from the server, including the address book that was created.
BUT: Syncing does nothing, and DAVx⁵ complains about having no Internet connection (even though that is the whole point here).

Expected result

It should just sync.

If it can set up the account, clearly it can, and Android lets it. It’s just a piece of code that artificially blocks it.

Further info

I run the following setup:
In normal state, my phone offers WIFI tethering, and my PC connects to it to go online.
But on my PC I also run Radicale, on a different WIFI device. So when I want to sync, I would disable tethering and mobile data, then enable wifi on my phone to make my PC the “router”.
Obviously my PC then has no connection to the Internet. (That is the point. It shouldn’t.)

Now I can open Radicale’s web interface perfectly fine in the browser on my phone.
And I can set up the DAV account perfectly fine in DAVx⁵.

But after that, I cannot sync. Ever. No matter what I configure.
It always complains that it has no Internet connection.

This is a piece of code that is really unnecessary.
I’m stuck with no contacts on my phone right now because of it. Worse (but not your fault), I lost all new contacts when my old phone broke, due to not being able to sync anymore for a few months now.

If it can connect to the server, it should work.
No matter if on the the Internet, a secure intranet, or even via localhost loopback or adb forwarding, etc.

I do not have any other way to go online, not only due to cost. Nor do I want to ever bring my Radicale server on the Internet.
And running Radicale on the IP the PC gets when tethered, doesn’t work anyway, mainly because the IP changes every time with modern Android, and DAVx5 doesn’t let me easily change the IP. (That would also be nice, if the host/port, and user/password were editable after account creation). Not that I would want to do that.

So: Can you fix this, by removing this artificial limitation?
Or at least let me turn it off with a switch?

Thank you!
(Otherwise it’s a great tool. I would donate, if I didn’t literally have no money.)