iOS 12.1.2 Not Connecting to private CalDav and CardDav server

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iOS 12.1.2 Not Connecting to private CalDav and CardDav server

I recently upgraded to iOS 12 on my iphone SE and 2018 iPad, and on both devices, I am unable to connect to a CalDav/CardDav server I host on a Synology NAS. In the Calendars App, under my CardDav calendar, it says "unable to connect to the internet".

Troubleshooting steps taken:

-Reboot and Soft Reboot (Power + Home Button)

-Verified that the server is reachable on non-iOS related devices (Thunderbird 65 on Windows 7/10, OnePlus 3T Android Oreo).

-Removed CalDav account and attempted to re-add the account. Confirmed the credentials are valid on other systems.

-Verified the port is open on yougetsignal.com and canyouseeme.org

-Tried to use both IP and DNS name in the server settings.

-Verified I can navigate to the server through Firefox and Safari on iPhone.

-Rebooted Router and Synology server.

Is there any other documented cased of iOS 12 having connectivity issues with calDav/cardDav protocol? Any insight is appreciated.

iPhone SE

Posted on Jan 7, 2019 12:34 AM

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Answer 1

konnor240 Author

Level 1

4 points

Jan 14, 2019 7:27 PM in response to konnor240

OP here. Turns out iOS 12 doesn't support CalDAV/CardDAV over http. You must use HTTPS. To solve this, you get import a cert to your Synology using a domain name you own (or DDNS through Synology) and receive a certificate through LetsEncrypt.

Information on how to do this is through Synology's support page here: https://www.synology.com/en-us/knowledgebase/DSM/help/DSM/AdminCenter/connection_certificate

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