FTP Connection Erro 421 - Client limit reached

mepi0011 · December 19, 2024, 8:15am

When I start the backup via FTP, I get the following error message after a while:

2024-12-18 16:04:38 +01 - [Error-Duplicati.Library.Main.Operation.BackupHandler-FatalError]: Fatal error

FtpCommandException: Code: 421 Message: Client limit reached. Try again later.
2024-12-18 16:04:38 +01 - [Error-Duplicati.Library.Main.Controller-FailedOperation]: Die Operation Backup ist mit folgenden Fehler fehlgeschlagen: One or more errors occurred. (Code: 421 Message: Client limit reached. Try again later. (Code: 421 Message: Client limit reached. Try again later.) (One or more errors occurred. (Code: 421 Message: Client limit reached. Try again later.)))

AggregateException: One or more errors occurred. (Code: 421 Message: Client limit reached. Try again later. (Code: 421 Message: Client limit reached. Try again later.) (One or more errors occurred. (Code: 421 Message: Client limit reached. Try again later.)))

I use latest Duplicati 2.1.0.2 from November 29. Duplicati runs on Windows Server 2019.
The FTP counterpart is a FTP (FTPS only) release on my FritzBox (Router).

Suggestions what causes the error?

ts678 · December 19, 2024, 12:52pm

Is this a new backup or one that worked on an older Duplicati before an upgrade to 2.1.0.2?

2.1.0.2 possibly needs one more connection, as ftp is now more like aftp, which needed it.

Is its client limit either known or settable?

If low and fixed, you can try lowering this Advanced option from default 4 to something lower:

asynchronous-concurrent-upload-limit

mepi0011 · December 19, 2024, 1:54pm

It’s a new backup.
I’m not yet experienced with Duplicati, the PC on which Duplicati is running is connected to a firewall and the FTP release on my router (Fritz!Box) is also new. Therefore, I currently have three possible error sources

On the router (Fritz!Box) I can’t set anything on the FTP or I haven’t found anything yet. Neither have I found any hints on the Internet. I have sent a support request to the manufacturer of the router.

ts678 · December 19, 2024, 2:29pm

If it has a low fixed limit (or while waiting for their support to say) you can lower Duplicati’s use.

In FileZilla Server, I tested that a limit of 2 was enough to do a backup with lots of remote files, provided I turned down the concurrent upload limit to 1. Two connections is odd. The end was

If Fritz!Box has a fixed limit of 1, this behavior may be troubling.

kenkendk · December 19, 2024, 10:43pm

I think the link you posted is for the previous FTP client (aka FtpWebRequest) that made one (control) connection per operation?

FluentFTP which is used now, has only one (control) connection, but for FTP you get a new connection for each file transfer (regardless of client).

Usually the connection is closed when no longer being used, and this frees up a port. If the operating system or something prevents the socket from shutting down cleanly, this will be in a wait state until a timeout occurs. If this happens often, you could easily exhaust the number of available ports on the FTP server.

If that happens, you should be able to use netstat or similar to see it. Figuring out why is harder.

ts678 · December 19, 2024, 10:55pm

The GitHub Issue comment is from Feb 15, but I’m pretty sure the FileZilla Server image is new. Supporting evidence for that is it shows the recent bug of percent-encoding test 2 as test%202.

If it helps any, the old issue was thinking that SFTP had the one-too-many connections quirk too.

I still have the FileZilla Server open. Session 49 was a whole lot of STOR. Session 48 looked like:

<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 [Response] 220-FileZilla Server 1.8.1
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 [Response] 220 Please visit https://filezilla-project.org/
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 [Command] USER duplicati
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 [Response] 331 Please, specify the password.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 [Command] PASS ****
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 [Response] 230 Login successful.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] FEAT
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 211-Features:
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 211 End
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] OPTS UTF8 ON
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 202 UTF8 mode is always enabled. No need to send this command
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] SYST
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 215 UNIX emulated by FileZilla.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] TYPE I
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 200 Type set to I
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||52609|)
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] MLSD /test%202
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 226 Operation successful

and we don’t hear from it again until its QUIT which is the last thing done. Why no QUIT sooner?

kenkendk · December 20, 2024, 7:38am

Not sure how the internals of FluentFTP are organized. From Duplicati’s perspective, there is one backend instance, and each backend instance has one FluentFTP instance.

I would expect this to translate to one control connection being used for all operations, but your observations suggests that there are two control connections.

Do you have the start of session 49? Does it look similar with a login and feature probe?

mepi0011 · December 20, 2024, 8:18am

In the meantime I reduce the concurrent-upload-limit and test different FTP settings with different error messages:

"Errors": [
    "2024-12-19 21:19:45 +01 - [Error-Duplicati.Library.Main.Operation.BackupHandler-FatalError]: Fatal error\r\nSocketException: Eine vorhandene Verbindung wurde vom Remotehost geschlossen.",
    "2024-12-19 21:19:45 +01 - [Error-Duplicati.Library.Main.Controller-FailedOperation]: Die Operation Backup ist mit folgenden Fehler fehlgeschlagen: One or more errors occurred. (Eine vorhandene Verbindung wurde vom Remotehost geschlossen. (Eine vorhandene Verbindung wurde vom Remotehost geschlossen.) (One or more errors occurred. (Eine vorhandene Verbindung wurde vom Remotehost geschlossen.)))\r\nAggregateException: One or more errors occurred. (Eine vorhandene Verbindung wurde vom Remotehost geschlossen. (Eine vorhandene Verbindung wurde vom Remotehost geschlossen.) (One or more errors occurred. (Eine vorhandene Verbindung wurde vom Remotehost geschlossen.)))"
  ]

or

"Errors": [
    "2024-12-19 18:49:28 +01 - [Error-Duplicati.Library.Main.Operation.BackupHandler-FatalError]: Fatal error\r\nTimeoutException: Timed out trying to read data from the socket stream!",
    "2024-12-19 18:49:28 +01 - [Error-Duplicati.Library.Main.Controller-FailedOperation]: Die Operation Backup ist mit folgenden Fehler fehlgeschlagen: One or more errors occurred. (Timed out trying to read data from the socket stream! (Timed out trying to read data from the socket stream!) (One or more errors occurred. (Timed out trying to read data from the socket stream!)))\r\nAggregateException: One or more errors occurred. (Timed out trying to read data from the socket stream! (Timed out trying to read data from the socket stream!) (One or more errors occurred. (Timed out trying to read data from the socket stream!)))"
  ]

PS: Please give me feedback if I should create a new ticket for these error messages.

ts678 · December 20, 2024, 12:30pm

Added 48 end and first two STOR of 49:

<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Command] MLSD /test%202
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:15:13 AM> FTP Session 48 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:15:40 AM> FTP Session 49 127.0.0.1 [Response] 220-FileZilla Server 1.8.1
<12/19/2024 9:15:40 AM> FTP Session 49 127.0.0.1 [Response] 220 Please visit https://filezilla-project.org/
<12/19/2024 9:15:40 AM> FTP Session 49 127.0.0.1 [Command] USER duplicati
<12/19/2024 9:15:40 AM> FTP Session 49 127.0.0.1 [Response] 331 Please, specify the password.
<12/19/2024 9:15:40 AM> FTP Session 49 127.0.0.1 [Command] PASS ****
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 [Response] 230 Login successful.
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] FEAT
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 211-Features:
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 211 End
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] OPTS UTF8 ON
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 202 UTF8 mode is always enabled. No need to send this command
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] SYST
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 215 UNIX emulated by FileZilla.
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-b3f3f570500a648ae8e19d12a1c870edf.dblock.zip
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 550 Couldn't open the file or directory
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] TYPE I
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 200 Type set to I
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||52617|)
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] STOR /test%202/duplicati-b3f3f570500a648ae8e19d12a1c870edf.dblock.zip
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-b3f3f570500a648ae8e19d12a1c870edf.dblock.zip
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 213 69315
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-i5cc084814d064410b47664adabeefd94.dindex.zip
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 550 Couldn't open the file or directory
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||52619|)
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] STOR /test%202/duplicati-i5cc084814d064410b47664adabeefd94.dindex.zip
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-i5cc084814d064410b47664adabeefd94.dindex.zip
<12/19/2024 9:15:41 AM> FTP Session 49 127.0.0.1 duplicati [Response] 213 587

Interestingly it doesn’t send the dlist in session 49, but creates 50 for that.
Session 51 looks like it might be list verification, and 52 a test download.

<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-ia0d7c7a316db44979464ecb7d38ee518.dindex.zip
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Response] 550 Couldn't open the file or directory
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||53461|)
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Command] STOR /test%202/duplicati-ia0d7c7a316db44979464ecb7d38ee518.dindex.zip
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-ia0d7c7a316db44979464ecb7d38ee518.dindex.zip
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Response] 213 10101
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Command] QUIT
<12/19/2024 9:18:17 AM> FTP Session 49 127.0.0.1 duplicati [Response] 221 Goodbye.
<12/19/2024 9:18:17 AM> FTP Server [Status] Session 49 ended gracefully.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 [Response] 220-FileZilla Server 1.8.1
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 [Response] 220 Please visit https://filezilla-project.org/
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 [Command] USER duplicati
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 [Response] 331 Please, specify the password.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 [Command] PASS ****
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 [Response] 230 Login successful.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] FEAT
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 211-Features:
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 211 End
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] OPTS UTF8 ON
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 202 UTF8 mode is always enabled. No need to send this command
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] SYST
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 215 UNIX emulated by FileZilla.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-20241219T141513Z.dlist.zip
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 550 Couldn't open the file or directory
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] TYPE I
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 200 Type set to I
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||53464|)
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] STOR /test%202/duplicati-20241219T141513Z.dlist.zip
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-20241219T141513Z.dlist.zip
<12/19/2024 9:18:17 AM> FTP Session 50 127.0.0.1 duplicati [Response] 213 742
<12/19/2024 9:18:18 AM> FTP Session 50 127.0.0.1 duplicati [Command] QUIT
<12/19/2024 9:18:18 AM> FTP Session 50 127.0.0.1 duplicati [Response] 221 Goodbye.
<12/19/2024 9:18:18 AM> FTP Server [Status] Session 50 ended gracefully.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 [Response] 220-FileZilla Server 1.8.1
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 [Response] 220 Please visit https://filezilla-project.org/
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 [Command] USER duplicati
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 [Response] 331 Please, specify the password.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 [Command] PASS ****
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 [Response] 230 Login successful.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] FEAT
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 211-Features:
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 211 End
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] OPTS UTF8 ON
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 202 UTF8 mode is always enabled. No need to send this command
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] SYST
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 215 UNIX emulated by FileZilla.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] TYPE I
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 200 Type set to I
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||53467|)
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Command] MLSD /test%202
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:18:18 AM> FTP Session 51 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:19:30 AM> FTP Session 51 127.0.0.1 duplicati [Command] QUIT
<12/19/2024 9:19:30 AM> FTP Session 51 127.0.0.1 duplicati [Response] 221 Goodbye.
<12/19/2024 9:19:30 AM> FTP Server [Status] Session 51 ended gracefully.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 [Response] 220-FileZilla Server 1.8.1
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 [Response] 220 Please visit https://filezilla-project.org/
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 [Command] USER duplicati
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 [Response] 331 Please, specify the password.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 [Command] PASS ****
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 [Response] 230 Login successful.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] FEAT
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 211-Features:
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 211 End
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] OPTS UTF8 ON
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 202 UTF8 mode is always enabled. No need to send this command
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] SYST
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 215 UNIX emulated by FileZilla.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] PWD
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 257 "/" is current directory.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-20241215T165416Z.dlist.zip
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 213 666
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] TYPE I
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 200 Type set to I
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||53481|)
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] RETR /test%202/duplicati-20241215T165416Z.dlist.zip
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-i61bcbc0a09304dab8453c38c33729d94.dindex.zip
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 213 587
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||53483|)
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] RETR /test%202/duplicati-i61bcbc0a09304dab8453c38c33729d94.dindex.zip
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] SIZE /test%202/duplicati-b2c6eb577841b4cce945ebf37e5a906a4.dblock.zip
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 213 1044786
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] EPSV
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Response] 229 Entering Extended Passive Mode (|||53485|)
<12/19/2024 9:19:30 AM> FTP Session 52 127.0.0.1 duplicati [Command] RETR /test%202/duplicati-b2c6eb577841b4cce945ebf37e5a906a4.dblock.zip
<12/19/2024 9:19:31 AM> FTP Session 52 127.0.0.1 duplicati [Response] 150 Starting data transfer.
<12/19/2024 9:19:31 AM> FTP Session 52 127.0.0.1 duplicati [Response] 226 Operation successful
<12/19/2024 9:19:31 AM> FTP Session 52 127.0.0.1 duplicati [Command] QUIT
<12/19/2024 9:19:31 AM> FTP Session 52 127.0.0.1 duplicati [Response] 221 Goodbye.
<12/19/2024 9:19:31 AM> FTP Server [Status] Session 52 ended gracefully.
<12/19/2024 9:19:31 AM> FTP Session 48 127.0.0.1 duplicati [Command] QUIT
<12/19/2024 9:19:31 AM> FTP Session 48 127.0.0.1 duplicati [Response] 221 Goodbye.
<12/19/2024 9:19:31 AM> FTP Server [Status] Session 48 ended gracefully

kenkendk · December 20, 2024, 12:34pm

Thanks! I will try to debug on my system and see if I can figure out why it would create multiple sessions.

There is an older related topic here that also mentions error 421 with FluentFTP.

That issue also details the multiple connections, so maybe the problem has been there for a while, but most people fixed it by using the FtpWebRequest based backend.

Edit: Also related issue: