WebDAV with Linux: Connection Times Out

I’ve tried creating a backup script on multiple Linux machines (running Ubuntu server/desktop) now to upload to my WebDAV server and I keep getting the same issue where I get to “Listing remote folder…” then everything just crashes.

Using the local system as the backup location works just fine, so the program is functioning, just the WebDAV protocol doesn’t work.
I’ve also deployed the script on multiple Windows machines just fine.

Script is basically:
duplicati-cli backup webdav://user:password@backup.server:8081/Folder/backup “/” --no-encryption

The actual script is a bit longer, as I’ve specified other flags, but modifying flags and the backup source doesn’t fix anything. I can literally put webdav://1 as the remote path and it still hangs when attempting to list the remote folder. I put the output below.

Backup started at 9/24/2021 10:02:48 PM
Checking remote backup …
Listing remote folder …
Listing remote folder …
Listing remote folder …
Listing remote folder …
Listing remote folder …
Fatal error => The request requires buffering data to succeed.

System.Net.WebException: The request requires buffering data to succeed.
at System.Net.HttpWebRequest.GetResponseFromData (System.Net.WebResponseStream stream, System.Threading.CancellationToken cancellationToken) [0x0017e] in :0
at System.Net.HttpWebRequest.RunWithTimeoutWorker[T] (System.Threading.Tasks.T ask1[TResult] workerTask, System.Int32 timeout, System.Action abort, System.Fun c1[TResult] aborted, System.Threading.CancellationTokenSource cts) [0x00118] in :0
at Duplicati.Library.Main.BackendManager.List () [0x00049] in :0
at Duplicati.Library.Main.Operation.FilelistProcessor.RemoteListAnalysis (Dupl icati.Library.Main.BackendManager backend, Duplicati.Library.Main.Options option s, Duplicati.Library.Main.Database.LocalDatabase database, Duplicati.Library.Mai n.IBackendWriter log, System.Collections.Generic.IEnumerable1[T] protectedFiles ) [0x0000d] in <e60bc008dd1b454d861cfacbdd3760b9>:0 at Duplicati.Library.Main.Operation.FilelistProcessor.VerifyRemoteList (Duplic ati.Library.Main.BackendManager backend, Duplicati.Library.Main.Options options, Duplicati.Library.Main.Database.LocalDatabase database, Duplicati.Library.Main. IBackendWriter log, System.Collections.Generic.IEnumerable1[T] protectedFiles) [0x00000] in :0
at Duplicati.Library.Main.Operation.BackupHandler.PreBackupVerify (Duplicati.L ibrary.Main.BackendManager backend, System.String protectedfile) [0x0011d] in <e 60bc008dd1b454d861cfacbdd3760b9>:0
at Duplicati.Library.Main.Operation.BackupHandler.RunAsync (System.String so urces, Duplicati.Library.Utility.IFilter filter, System.Threading.CancellationTo ken token) [0x01048] in :0
at CoCoL.ChannelExtensions.WaitForTaskOrThrow (System.Threading.Tasks.Task tas k) [0x00050] in <9a758ff4db6c48d6b3d4d0e5c2adf6d1>:0
at Duplicati.Library.Main.Operation.BackupHandler.Run (System.String sources , Duplicati.Library.Utility.IFilter filter, System.Threading.CancellationToken t oken) [0x00009] in :0
at Duplicati.Library.Main.Controller+<>c__DisplayClass14_0.b__0 (Dupli cati.Library.Main.BackupResults result) [0x0004b] in <e60bc008dd1b454d861cfacbdd 3760b9>:0
at Duplicati.Library.Main.Controller.RunAction[T] (T result, System.String& paths, Duplicati.Library.Utility.IFilter& filter, System.Action1[T] method) [0x 0026f] in <e60bc008dd1b454d861cfacbdd3760b9>:0 at Duplicati.Library.Main.Controller.Backup (System.String[] inputsources, Dup licati.Library.Utility.IFilter filter) [0x00074] in <e60bc008dd1b454d861cfacbdd3 760b9>:0 at Duplicati.CommandLine.Commands.Backup (System.IO.TextWriter outwriter, Syst em.Action1[T] setup, System.Collections.Generic.List1[T] args, System.Collecti ons.Generic.Dictionary2[TKey,TValue] options, Duplicati.Library.Utility.IFilter filter) [0x00119] in :0
at (wrapper delegate-invoke) System.Func6[System.IO.TextWriter,System.Action 1[Duplicati.Library.Main.Controller],System.Collections.Generic.List1[System.St ring],System.Collections.Generic.Dictionary2[System.String,System.String],Dupli cati.Library.Utility.IFilter,System.Int32].invoke_TResult_T1_T2_T3_T4_T5(System. IO.TextWriter,System.Action1<Duplicati.Library.Main.Controller>,System.Collecti ons.Generic.List1,System.Collections.Generic.Dictionary2<string, strin g>,Duplicati.Library.Utility.IFilter) at Duplicati.CommandLine.Program.ParseCommandLine (System.IO.TextWriter outwri ter, System.Action1[T] setup, System.Boolean& verboseErrors, System.String ar gs) [0x00342] in :0
at Duplicati.CommandLine.Program.RunCommandLine (System.IO.TextWriter outwrite r, System.IO.TextWriter errwriter, System.Action`1[T] setup, System.String arg s) [0x00002] in :0

Welcome to the forum @Kelton_Hathaway

Is this a server that you admin? Does it have any logs to see? Are you able to say what software this is?

Multiple Linux machines failing and multiple Windows machines working suggests a Linux-only problem.

Putting error message to a Google search got The request requires buffering data to succeed HttpClient which pointed to some mono code that causes that message, looking like server redirect might factor in.

That answer suggested looking at the unencrypted HTTP traffic. That might be difficult to actually set up.
If need be, a Windows Duplicati might be able to use Network Tracing in the .NET Framework to watch unencrypted traffic from the Duplicati side to test the redirect theory. It’s hard, but maybe a bit less hard.
Posting any quotes from it should be avoided, because there are some normally-encrypted secrets in it.

A simple test that might fail a folder listing the same way is Test connection on Destination screen.
Logging will possibly be different, but the test is basically a folder listing. Contents aren’t verified though.

If you are comfortable with the curl program, that might be another way to see if server does a redirect.

What sorts of versions? Make sure that mono --version reports at least 5.10. Latest is now