Caldav Probleme nach Port wechsel

[HefeHannes]

Guten Abend Community,

habe meine DS220j, an einer FritzBox hängen, und diese mittels DyDNS von außen zugänglich gemacht.
Vor einigen Tagen habe ich den Standard Port 5001 zu 6666 (fiktiv) geändert.

Hat auch wunderbar funktioniert, musste mich nur auf dem Smartphone in DS-File, Note & Photo neu einloggen.

Nur in der OneCalendar app funktioniert dies nicht, weder via lokaler Adresse noch von außen. Port und sämtliche anderen Infos passen sicher.
Folgenden Fehler gibt's immer:
An error occurred while sending the request : NO RESPONSE

Action: CheckAccountStatus

XCalendarApp.CalDavProvider.DavAccountRequestException: An error occurred while sending the request : NO RESPONSE ---> XCalendarApp.Common.Net.HttpException: An error occurred while sending the request ---> System.Net.Http.HttpRequestException: An error occurred while sending the request ---> System.Net.WebException: Error: ConnectFailure (Connection refused) ---> System.Net.Sockets.SocketException: Connection refused
at System.Net.Sockets.SocketAsyncResult.CheckIfThrowDelayedException () <0x733b31c79c + 0x000ac> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.Sockets.Socket.EndConnect (System.IAsyncResult asyncResult) <0x733b313404 + 0x0007f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection+<>c.<Connect>b__16_1 (System.IAsyncResult asyncResult) <0x733b300ed4 + 0x0006f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) [0x00019] in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x001e1] in <840d5dda0035423dbdb338172d2a7a58>:0
--- End of inner exception stack trace ---
at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x0025d] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection.InitConnection (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x000cc] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebOperation.Run () [0x0009a] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebCompletionSource`1[T].WaitForCompletion () <0x733b2ff5a8 + 0x0024f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.RunWithTimeoutWorker[T] (System.Threading.Tasks.Task`1[TResult] workerTask, System.Int32 timeout, System.Action abort, System.Func`1[TResult] aborted, System.Threading.CancellationTokenSource cts) <0x733b384c50 + 0x0054c> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) <0x733b2f4c40 + 0x000b8> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) <0x733e40bc60 + 0x00067> in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x0041b] in <ab47bb4827974b51bb5a33abcf2496e6>:0
--- End of inner exception stack trace ---
at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x00476] in <ab47bb4827974b51bb5a33abcf2496e6>:0
at System.Net.Http.HttpClient.FinishSendAsyncBuffered (System.Threading.Tasks.Task`1[TResult] sendTask, System.Net.Http.HttpRequestMessage request, System.Threading.CancellationTokenSource cts, System.Boolean disposeCts) [0x0017e] in <ab47bb4827974b51bb5a33abcf2496e6>:0
at XCalendarApp.Common.Net.CalendarHttpClient.ExecuteRequest (System.Threading.CancellationToken cancellationToken, System.String url, System.String httpMethod, System.String requestContent, System.String soapAction) [0x00276] in <8e9678fa97144123bb4a5bafd314fbce>:0
--- End of inner exception stack trace ---
at XCalendarApp.Common.Net.CalendarHttpClient.ExecuteRequest (System.Threading.CancellationToken cancellationToken, System.String url, System.String httpMethod, System.String requestContent, System.String soapAction) [0x004b6] in <8e9678fa97144123bb4a5bafd314fbce>:0
at XCalendarApp.CalDavProvider.DavHttpWebRequest.Request (System.Uri url, System.String httpMethod, System.String contentType, System.String requestContent, System.Int32 maxRedirects) [0x000ed] in <f373407d60214f4280d4d13a7f1ce8ff>:0
--- End of inner exception stack trace ---
at XCalendarApp.CalDavProvider.DavHttpWebRequest.Request (System.Uri url, System.String httpMethod, System.String contentType, System.String requestContent, System.Int32 maxRedirects) [0x002ce] in <f373407d60214f4280d4d13a7f1ce8ff>:0
at XCalendarApp.CalDavProvider.DavHttpWebRequest.Request (System.Uri url, System.String method, System.String contentType, System.String requestContent) <0x73358d65bc + 0x00127> in <f373407d60214f4280d4d13a7f1ce8ff>:0
at Dav.Client.Common.DavCommon.Request (System.Uri url, System.String method, System.String contentType, System.String requestContent, System.Collections.Generic.Dictionary`2[TKey,TValue] headers) [0x000e2] in <f56deadeacd74c3bae693356bcd1d51b>:0
at Dav.Client.CalDav.CalDavServer.GetOptions () <0x73358917f0 + 0x0011b> in <f56deadeacd74c3bae693356bcd1d51b>:0
at Dav.Client.CalDav.CalDavServer.Create (System.Uri url, Dav.Client.Common.IConnection connection) <0x7335890d44 + 0x00173> in <f56deadeacd74c3bae693356bcd1d51b>:0
at XCalendarApp.CalDavBaseProvider.CalDavBaseAccount`1[TCachedCalDavBaseCalendar].GetCalDavClient (XCalendarApp.Model.Settings.AccountSecurityInfo accountSecurityInfo) <0x733581c2dc + 0x00117> in <fae083817ada44479291bc758539a4dc>:0
at XCalendarApp.CalDavBaseProvider.CalDavBaseAccount`1[TCachedCalDavBaseCalendar].CheckProviderAccountInfo (XCalendarApp.Model.Settings.AccountSecurityInfo accountSecurityInfo) <0x733581b4c8 + 0x0011f> in <fae083817ada44479291bc758539a4dc>:0
at XCalendarApp.ProviderBase.AccountProviderBase`9[TCachedCalendar,TProviderCalendarItem,TCachedAppointment,TProviderAppointmentItem,TCachedContacts,TCachedContact,TProviderContactItem,TAppointmentDbData,TAccountOptions].CheckAccountStatus (XCalendarApp.Model.Data.SyncResults.AccountSyncResult accountSyncResult) <0x7335a3ba40 + 0x001b7> in <486d19f8ca8c4c0d9740bc42f807a0f1>:0
RequestType: OPTIONS
RequestUrl: https:// ei edomain. de:6666/caldav/ich

Inner exception: XCalendarApp.Common.Net.HttpException: An error occurred while sending the request ---> System.Net.Http.HttpRequestException: An error occurred while sending the request ---> System.Net.WebException: Error: ConnectFailure (Connection refused) ---> System.Net.Sockets.SocketException: Connection refused
at System.Net.Sockets.SocketAsyncResult.CheckIfThrowDelayedException () <0x733b31c79c + 0x000ac> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.Sockets.Socket.EndConnect (System.IAsyncResult asyncResult) <0x733b313404 + 0x0007f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection+<>c.<Connect>b__16_1 (System.IAsyncResult asyncResult) <0x733b300ed4 + 0x0006f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) [0x00019] in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x001e1] in <840d5dda0035423dbdb338172d2a7a58>:0
--- End of inner exception stack trace ---
at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x0025d] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection.InitConnection (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x000cc] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebOperation.Run () [0x0009a] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebCompletionSource`1[T].WaitForCompletion () <0x733b2ff5a8 + 0x0024f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.RunWithTimeoutWorker[T] (System.Threading.Tasks.Task`1[TResult] workerTask, System.Int32 timeout, System.Action abort, System.Func`1[TResult] aborted, System.Threading.CancellationTokenSource cts) <0x733b384c50 + 0x0054c> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) <0x733b2f4c40 + 0x000b8> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) <0x733e40bc60 + 0x00067> in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x0041b] in <ab47bb4827974b51bb5a33abcf2496e6>:0
--- End of inner exception stack trace ---
at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x00476] in <ab47bb4827974b51bb5a33abcf2496e6>:0
at System.Net.Http.HttpClient.FinishSendAsyncBuffered (System.Threading.Tasks.Task`1[TResult] sendTask, System.Net.Http.HttpRequestMessage request, System.Threading.CancellationTokenSource cts, System.Boolean disposeCts) [0x0017e] in <ab47bb4827974b51bb5a33abcf2496e6>:0
at XCalendarApp.Common.Net.CalendarHttpClient.ExecuteRequest (System.Threading.CancellationToken cancellationToken, System.String url, System.String httpMethod, System.String requestContent, System.String soapAction) [0x00276] in <8e9678fa97144123bb4a5bafd314fbce>:0
--- End of inner exception stack trace ---
at XCalendarApp.Common.Net.CalendarHttpClient.ExecuteRequest (System.Threading.CancellationToken cancellationToken, System.String url, System.String httpMethod, System.String requestContent, System.String soapAction) [0x004b6] in <8e9678fa97144123bb4a5bafd314fbce>:0
at XCalendarApp.CalDavProvider.DavHttpWebRequest.Request (System.Uri url, System.String httpMethod, System.String contentType, System.String requestContent, System.Int32 maxRedirects) [0x000ed] in <f373407d60214f4280d4d13a7f1ce8ff>:0
Inner exception: System.Net.Http.HttpRequestException: An error occurred while sending the request ---> System.Net.WebException: Error: ConnectFailure (Connection refused) ---> System.Net.Sockets.SocketException: Connection refused
at System.Net.Sockets.SocketAsyncResult.CheckIfThrowDelayedException () <0x733b31c79c + 0x000ac> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.Sockets.Socket.EndConnect (System.IAsyncResult asyncResult) <0x733b313404 + 0x0007f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection+<>c.<Connect>b__16_1 (System.IAsyncResult asyncResult) <0x733b300ed4 + 0x0006f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) [0x00019] in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x001e1] in <840d5dda0035423dbdb338172d2a7a58>:0
--- End of inner exception stack trace ---
at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x0025d] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection.InitConnection (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x000cc] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebOperation.Run () [0x0009a] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebCompletionSource`1[T].WaitForCompletion () <0x733b2ff5a8 + 0x0024f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.RunWithTimeoutWorker[T] (System.Threading.Tasks.Task`1[TResult] workerTask, System.Int32 timeout, System.Action abort, System.Func`1[TResult] aborted, System.Threading.CancellationTokenSource cts) <0x733b384c50 + 0x0054c> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) <0x733b2f4c40 + 0x000b8> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) <0x733e40bc60 + 0x00067> in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x0041b] in <ab47bb4827974b51bb5a33abcf2496e6>:0
--- End of inner exception stack trace ---
at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x00476] in <ab47bb4827974b51bb5a33abcf2496e6>:0
at System.Net.Http.HttpClient.FinishSendAsyncBuffered (System.Threading.Tasks.Task`1[TResult] sendTask, System.Net.Http.HttpRequestMessage request, System.Threading.CancellationTokenSource cts, System.Boolean disposeCts) [0x0017e] in <ab47bb4827974b51bb5a33abcf2496e6>:0
at XCalendarApp.Common.Net.CalendarHttpClient.ExecuteRequest (System.Threading.CancellationToken cancellationToken, System.String url, System.String httpMethod, System.String requestContent, System.String soapAction) [0x00276] in <8e9678fa97144123bb4a5bafd314fbce>:0
Inner exception: System.Net.WebException: Error: ConnectFailure (Connection refused) ---> System.Net.Sockets.SocketException: Connection refused
at System.Net.Sockets.SocketAsyncResult.CheckIfThrowDelayedException () <0x733b31c79c + 0x000ac> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.Sockets.Socket.EndConnect (System.IAsyncResult asyncResult) <0x733b313404 + 0x0007f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection+<>c.<Connect>b__16_1 (System.IAsyncResult asyncResult) <0x733b300ed4 + 0x0006f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) [0x00019] in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x001e1] in <840d5dda0035423dbdb338172d2a7a58>:0
--- End of inner exception stack trace ---
at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x0025d] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection.InitConnection (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x000cc] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebOperation.Run () [0x0009a] in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebCompletionSource`1[T].WaitForCompletion () <0x733b2ff5a8 + 0x0024f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.RunWithTimeoutWorker[T] (System.Threading.Tasks.Task`1[TResult] workerTask, System.Int32 timeout, System.Action abort, System.Func`1[TResult] aborted, System.Threading.CancellationTokenSource cts) <0x733b384c50 + 0x0054c> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) <0x733b2f4c40 + 0x000b8> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) <0x733e40bc60 + 0x00067> in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.Http.MonoWebRequestHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x0041b] in <ab47bb4827974b51bb5a33abcf2496e6>:0
Inner exception: System.Net.Sockets.SocketException (0x80004005): Connection refused
at System.Net.Sockets.SocketAsyncResult.CheckIfThrowDelayedException () <0x733b31c79c + 0x000ac> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.Sockets.Socket.EndConnect (System.IAsyncResult asyncResult) <0x733b313404 + 0x0007f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Net.WebConnection+<>c.<Connect>b__16_1 (System.IAsyncResult asyncResult) <0x733b300ed4 + 0x0006f> in <840d5dda0035423dbdb338172d2a7a58>:0
at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func`2[T,TResult] endFunction, System.Action`1[T] endAction, System.Threading.Tasks.Task`1[TResult] promise, System.Boolean requiresSynchronization) [0x00019] in <5beae699dde34c2a82650f62aa513c30>:0
--- End of stack trace from previous location where exception was thrown ---

at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x001e1] in <840d5dda0035423dbdb338172d2a7a58>:0


Über helfende Beiträge würde ich mich freuen.

Schönen Abend noch

 

[waldemard]

Warum sind da Leerstellen im URL?

https:// ei xxxyyyzzz. de:6666/caldav/ich

 

[HefeHannes]

Da war meine echte Domain drinen, habe ich übers Handy geändert.

 

[MattCB]

Der DSM-Port ist nicht unbedingt auch der Port für CalDAV.

Also wenn ich auf deine URL klicke, steht da immer noch Port 5001 und man sieht deine richtige Domain.

Ich habe bei mir den Kalender und die Kontakte auf eine eigene Subdomain gelegt (siehe Screenshot). Somit ist der verwendete Port egal, da die Synology im Hintergrund wahrscheinlich einen Reverse-Proxy dafür anlegt.

Du kannst ja mal unter Systemsteuerung / Anmeldeportal / Anwendungen eigene Ports für CalDAV vergeben und diese dann testen. Ob das mit der eigenen Subdomain bei deinem DynDNS geht, weiß ich nicht, ich nutze eine Synology-DDNS-Adresse, da sind Subdomains kein Problem.

 

[waldemard]

Da war meine echte Domain drinen, habe ich übers Handy geändert.

Oh. OK ich stand auf der Leitung

 

[HefeHannes]

Guten Abend Leute,

neues von meinem kleinen problemchen...
Zuerst einmal, ist das Log im Startpost, quatsch... da dieses noch auf den alten Port bezogen war.
Irgendwie scheint etwas mit den Zertifikaten nicht in Ordnung zu sein, denn wenn ich in OneCalendar unter "Sicherheitsoptionen" die Option Validiere Zertifikate deaktiviere, synchronisiert er sauber durch.

Alle Dienste sind bei mir auf die Zertifikate, meinedomain.de, eingestellt.
Das Zertifikat hierfür habe ich erst bei LetsEncrypt erneuert.

Selbiges Problem besteht übrigens auch, wenn ich das Standard Synology Zertifikat wähle.

 

[waldemard]

bei mir steht beim Synology Zert. "selbstsigniertes Zertifikat...". Kann es sein dass die selbstsignierten u. die LetsEncrypt nicht akzeptiert werden?

 

[HefeHannes]

Glaubs fast nicht, da vorm portwechsel von 5001 nach 6666 alles funktioniert hat.

 

[waldemard]

Noch eine banale Frage. Hast Du mit nmap geprüft ob der 6666 Port auf deiner Syno offen ist?

 

[HefeHannes]

Nein, habe ich tatsächlich nicht.
Aber über den Browser ist der Kalender ja erreichbar unter besagten Port - sowohl von außen als auch lokal.

 

[waldemard]

Dann ist der Port eindeutig offen und der "Fehler" liegt in der App. Fällt mir nur der Wireshark ein um zu prüfen ob die App wirklich Port 6666 anfragt.

 

[HefeHannes]

Dann ist der Port eindeutig offen und der "Fehler" liegt in der App. Fällt mir nur der Wireshark ein um zu prüfen ob die App wirklich Port 6666 anfragt.

Ist mir gerade auf die schnelle zu kompliziert.
Unter iOS funktioniert alles bestens, mit DAVx⁵ unter Android auch, liegt also am OneCalendar.