Authentication failed because the remote party has closed the transport stream

Running a backup: Authentication failed because the remote party has closed the transport stream?

What back end type are you using?

It’s a QNAP NAS, connected through FTPS.

Ok I recognize you now from the other thread on this same/similar issue. Maybe we can continue the discussion there. My last post had something for you to try.

This thread concerns a different problem, as I am now actually backing up now, but if you prefer to move there, that is okay for me.

Ok thanks for the clarification. If this is a different problem we can continue discussion here.

So your backup starts and runs for a while? (How long?) Then at some point you get the “remote party has closed” error?

My backup says “Counting …”, runs for 3 minutes and then terminates with One or more errors occurred. (Authentication failed because the remote party has closed the transport stream. (Authentication failed because the remote party has closed the transport stream.) (One or more errors occurred. (Authentication failed because the remote party has closed the transport stream.)))

Are you able to see logs on the FTP server side?

All I can see is about 25 login/logouts.

What port number did you set on page 2 of your backup config? I saw in the other thread that 21 and 990 seem to work, but maybe that is true just for the connection test. If it’s set to 21, can you change it to 990 and try again?

The port number doesn’t make a difference.

Are you able to use a standalone FTPS client (maybe FileZilla) as a test? Use the same credentials as Duplicati is using, and see if you can transfer files to/from the destination you configured in Duplicati.

Just trying to figure out if the problem is on the FTP server side or the Duplicati side.

Yes, I can transfer files through lftp, and I can mount my nas as a share through ftps.

With FTPS I would recommend using AFTP instead of FTPS. I had lot of problems with FTPS, currently using AFTP and knock knock, everything is working at least reasonably well. Yet I did change so many things when updating “everything at once” that I can’t be sure if that was a meaningful change or not.

Also it seems that some times idle FTP control sessions are left open. I’ve set suitable timeout for those. But I didn’t figure out the exact logic how the sessions work. Anyway, it’s not a problem with timeout, but it gave me slight impression that something isn’t working exactly as it should. Ie, does FTPS sessions get properly terminated when transfer(s) are done. The timeout doesn’t seem to bother Duplicati, then it just logs in again, if the timeout has been reached.

I don’t think Duplicati is production strength yet. I have wasted enough of my time, so I tossed it.

Yup, if you’ve seen this tread, lots of issues, hard to solve issues, and “logical” issues, the system just breaks down.

FTP and FTPS are probably the least reliable of the protocols Duplicati supports. There are so many differences between various FTP servers and how they respond, lay out directory listings, etc. Sometimes switching between “FTP” and “FTP (Alternative)” can help.

Personally I would avoid FTP/FTPS if at all possible! (This does not include SFTP which is SSH-based and is quite reliable.)