Which ports are used when connecting to Synology Calendar?

[carforge]

Hello.

Until today, I was syncing my calendar on my Android Phone with DAVX5 which worked fine so far. (Scenario 1)

In this scenario 1 I've used a VPS for tunneling (6tunnel) my traffic to my home router which is only reachable by IPv6 addresses. Then I have opened a port in my router and forwarded it to my NAS.

In order to reduce the open ports on my router, I ordered a new VPS and set up a reverse proxy and connected this VPS via OpenVPN to my NAS. So all traffic will be routed through my VPN to the NAS. Everything works fine. I am able to open the calendar web page. I am also able to connect my Android Phone via DAVX5 to the CALDAV service (it seems to work - no error messages). But in DAVX5 my calendars are not listed. Are there any firewall ports to be opened in the reverse proxy VPS? (I also needed to make the VPS accessible by HTTP/HTTPS: https://docs.oracle.com/en-us/iaas/developer-tutorials/tutorials/apache-on-ubuntu/01oci-ubuntu-apache-summary.htm)

[rfc2822]

Hi,

I am also able to connect my Android Phone via DAVX5 to the CALDAV service (it seems to work - no error messages). But in DAVX5 my calendars are not listed.

Then this doesn't sound like a connection problem. Are there any (maybe transparent) HTTP (reverse) proxies or something like that involved? They may rewrite the WebDAV requests so that they don't work anymore. WebDAV uses URLs and paths in the payload, and reverse proxies normally only rewrite the requests itself (and maybe headers like Location). So I'm quite sure that the Reverse proxy in your image is the problem.

For details or if this is not the case, you can

• enable verbose logs in DAVx⁵
• add the account / refresh the calendar/address book list if the account is already there,
• view the verbose logs to see whats happening.

[carforge]

Good shot! I think I found the issue:

2022-03-21 10:05:29 2 [CustomCertService] CustomCertService created
2022-03-21 10:05:29 61501 [ui.setup.DavResourceFinder] Finding initial carddav service configuration
2022-03-21 10:05:29 61501 [ui.setup.DavResourceFinder] Checking user-given URL: https://home.my-domain.de/cal/caldav/my_username
2022-03-21 10:05:29 61501 [HttpClient] --> PROPFIND https://home.my-domain.de/cal/caldav/my_username http/1.1
2022-03-21 10:05:29 61501 [HttpClient] Depth: 0
2022-03-21 10:05:29 61501 [HttpClient] User-Agent: DAVx5/4.2-gplay (2022/03/18; dav4jvm; okhttp/4.9.3) Android/11
2022-03-21 10:05:29 61501 [HttpClient] Accept-Language: de-DE, de;q=0.7, *;q=0.5
2022-03-21 10:05:29 61501 [HttpClient] Content-Type: application/xml; charset=utf-8
2022-03-21 10:05:29 61501 [HttpClient] Content-Length: 290
2022-03-21 10:05:29 61501 [HttpClient] Host: home.my-domain.de
2022-03-21 10:05:29 61501 [HttpClient] Connection: Keep-Alive
2022-03-21 10:05:29 61501 [HttpClient] Accept-Encoding: gzip
2022-03-21 10:05:29 61501 [HttpClient] 
2022-03-21 10:05:29 61501 [HttpClient] <?xml version='1.0' encoding='UTF-8' ?><propfind xmlns="DAV:" xmlns:CAL="urn:ietf:params:xml:ns:caldav" xmlns:CARD="urn:ietf:params:xml:ns:carddav"><prop><resourcetype /><displayname /><CARD:addressbook-description /><CARD:addressbook-home-set /><current-user-principal /></prop></propfind>
2022-03-21 10:05:29 61501 [HttpClient] --> END PROPFIND (290-byte body)
2022-03-21 10:05:29 61501 [at.bitfire.dav4jvm.BasicDigestAuthHandler] Trying Basic auth preemptively
2022-03-21 10:05:29 61501 [at.bitfire.dav4jvm.BasicDigestAuthHandler] Adding Basic authorization header for https://home.my-domain.de/cal/caldav/my_username
2022-03-21 10:05:30 61501 [HttpClient] <-- 207 Multi-Status https://home.my-domain.de/cal/caldav/my_username (607ms)
2022-03-21 10:05:30 61501 [HttpClient] Server: nginx/1.18.0 (Ubuntu)
2022-03-21 10:05:30 61501 [HttpClient] Date: Mon, 21 Mar 2022 09:05:31 GMT
2022-03-21 10:05:30 61501 [HttpClient] Content-Type: text/xml; charset="utf-8"
2022-03-21 10:05:30 61501 [HttpClient] Content-Length: 703
2022-03-21 10:05:30 61501 [HttpClient] Connection: keep-alive
2022-03-21 10:05:30 61501 [HttpClient] Content-Location: /caldav.php/my_username/
2022-03-21 10:05:30 61501 [HttpClient] DAV: 1, 2, 3, access-control, calendar-access, calendar-schedule
2022-03-21 10:05:30 61501 [HttpClient] DAV: extended-mkcol, bind, addressbook, calendar-auto-schedule
2022-03-21 10:05:30 61501 [HttpClient] ETag: "d2a590f20709cfa302672f60acd682f5"
2022-03-21 10:05:30 61501 [HttpClient] X-DAViCal-Version: DAViCal/1.1.9; DB/1.2.12
2022-03-21 10:05:30 61501 [HttpClient] 
2022-03-21 10:05:30 61501 [HttpClient] <?xml version="1.0" encoding="utf-8" ?>
<multistatus xmlns="DAV:" xmlns:VC="urn:ietf:params:xml:ns:carddav">
 <response>
  <href>/caldav.php/my_username/</href>
  <propstat>
   <prop>
    <resourcetype>
     <collection/>
     <principal/>
    </resourcetype>
    <displayname>my_username</displayname>
    <VC:addressbook-home-set>
     <href>/caldav.php/my_username/</href>
    </VC:addressbook-home-set>
    <current-user-principal>
     <href>/caldav.php/my_username/</href>
    </current-user-principal>
   </prop>
   <status>HTTP/1.1 200 OK</status>
  </propstat>
  <propstat>
   <prop>
    <VC:addressbook-description/>
   </prop>
   <status>HTTP/1.1 404 Not Found</status>
  </propstat>
 </response>
</multistatus>

2022-03-21 10:05:30 61501 [HttpClient] <-- END HTTP (703-byte body)
2022-03-21 10:05:30 61501 [ui.setup.DavResourceFinder] Found address book home-set at https://home.my-domain.de/caldav.php/my_username/
2022-03-21 10:05:30 61501 [HttpClient] --> OPTIONS https://home.my-domain.de/caldav.php/my_username/ http/1.1
2022-03-21 10:05:30 61501 [HttpClient] Content-Length: 0
2022-03-21 10:05:30 61501 [HttpClient] User-Agent: DAVx5/4.2-gplay (2022/03/18; dav4jvm; okhttp/4.9.3) Android/11
2022-03-21 10:05:30 61501 [HttpClient] Accept-Language: de-DE, de;q=0.7, *;q=0.5
2022-03-21 10:05:30 61501 [HttpClient] Host: home.my-domain.de
2022-03-21 10:05:30 61501 [HttpClient] Connection: Keep-Alive
2022-03-21 10:05:30 61501 [HttpClient] Accept-Encoding: gzip
2022-03-21 10:05:30 61501 [HttpClient] --> END OPTIONS
2022-03-21 10:05:30 61501 [at.bitfire.dav4jvm.BasicDigestAuthHandler] Adding Basic authorization header for https://home.my-domain.de/caldav.php/my_username/
2022-03-21 10:05:30 61501 [HttpClient] <-- 404 Not Found https://home.my-domain.de/caldav.php/my_username/ (17ms)
2022-03-21 10:05:30 61501 [HttpClient] Server: nginx/1.18.0 (Ubuntu)
2022-03-21 10:05:30 61501 [HttpClient] Date: Mon, 21 Mar 2022 09:05:31 GMT
2022-03-21 10:05:30 61501 [HttpClient] Content-Type: text/html
2022-03-21 10:05:30 61501 [HttpClient] Transfer-Encoding: chunked
2022-03-21 10:05:30 61501 [HttpClient] Connection: keep-alive
2022-03-21 10:05:30 61501 [HttpClient] Content-Encoding: gzip
2022-03-21 10:05:30 61501 [HttpClient] 
2022-03-21 10:05:30 61501 [HttpClient] <html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>nginx/1.18.0 (Ubuntu)</center>
</body>
</html>

2022-03-21 10:05:30 61501 [HttpClient] <-- END HTTP (162-byte, 123-gzipped-byte body)
2022-03-21 10:05:30 61501 [ui.setup.DavResourceFinder] Couldn't detect services on https://home.my-domain.de/caldav.php/my_username/
EXCEPTION at.bitfire.dav4jvm.exception.NotFoundException: HTTP 404 Not Found
	at at.bitfire.dav4jvm.DavResource.checkStatus(DavResource.kt:6)
	at at.bitfire.dav4jvm.DavResource.checkStatus(DavResource.kt:3)
	at at.bitfire.dav4jvm.DavResource.options(DavResource.kt:8)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder.providesService(DavResourceFinder.kt:2)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder.scanCardDavResponse(DavResourceFinder.kt:16)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder$checkUserGivenURL$1.invoke(DavResourceFinder.kt:2)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder$checkUserGivenURL$1.invoke(DavResourceFinder.kt:1)
	at at.bitfire.dav4jvm.Response$Companion.parse(Response.kt:38)
	at at.bitfire.dav4jvm.DavResource.processMultiStatus$parseMultiStatus(DavResource.kt:7)
	at at.bitfire.dav4jvm.DavResource.processMultiStatus(DavResource.kt:13)
	at at.bitfire.dav4jvm.DavResource.processMultiStatus(DavResource.kt:6)
	at at.bitfire.dav4jvm.DavResource.propfind(DavResource.kt:11)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder.checkUserGivenURL(DavResourceFinder.kt:11)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder.findInitialConfiguration(DavResourceFinder.kt:24)
	at at.bitfire.davdroid.ui.setup.DavResourceFinder.findInitialConfiguration(DavResourceFinder.kt:1)
	at at.bitfire.davdroid.ui.setup.DetectConfigurationFragment$DetectConfigurationModel$detectConfiguration$2.invoke(DetectConfigurationFragment.kt:6)
	at at.bitfire.davdroid.ui.setup.DetectConfigurationFragment$DetectConfigurationModel$detectConfiguration$2.invoke(DetectConfigurationFragment.kt:1)
	at kotlin.concurrent.ThreadsKt$thread$thread$1.run(Thread.kt:1)

As you can see, I add the account with https://home.my-domain.de/**cal**/caldav/my_username
It seems that when DAVx5 lookup the settings it receives the answer https://home.my-domain.de/caldav/my_username --> "/cal/" is missing!
Is this an Issue with my proxy, or do I have to define this in Synology Calendar?

[rfc2822]

It seems that when DAVx5 lookup the settings it receives the answer https://home.my-domain.de/caldav/my_username --> "/cal/" is missing!

That's exactly the problem. There could be various methods to solve that, including

• a WebDAV-capable reverse proxy (I don't know if there are any),
• setting the "correct" base path prefix in your WebDAV/CalDAV server (I don't think Synology Calendar can do that).

My suggestion is to use a solution where no URL rewriting is required, because it doesn't work well with WebDAV (it's hacky enough with plain HTTP).

[carforge]

I finally made it...

I created 2 sub-domains:
https://cal.my-domain.de/
https://card.my-domain.de/

For each domain I have a dedicated "proxy destination" through my VPN (e.g.: proxy_pass https://ip_of_my_NAS:port_of_application;)

Web application works, DAVX5 works.