Let's see if more people ask for this.

martin wrote:

Thanks for your report.
...
Please contact Wasabi support and ask them to fix their FTP interface.

Thanks Martin for your verification.
Is it possible to implement some workaround (e.g. in the configuration parameters) like: "Continue even if a directory listing fails" ?
My point is that WinSCP aborts the connection when this event happen.
Maybe some parameter might allow to connect anyway, despite a directory listing failed (and the directory is considered, necessarily, empty or not even shown)

Thanks, Pablo

P.S.
Please note that it's totally clear to me that the problem is 100% server side, no doubt !
My point is since I don't think they will fix the server (they probably use some close solution to implement a virtual ftp filesystem over their cloud) maybe a simple workaround would be / is already possible in the configuration of the client. This is what, for example, YummyFTP for mac does.

Thanks for your report.
I've created a trial account and I was able to reproduce the problem.
Though, I'm pretty sure that it's server-side problem. Their FTP server/interface does not close a transfer connection for a directory listing, when a directory is empty.
I've tested other FTP clients, some have the same problem as WinSCP (e.g. FileZilla), some not (e.g. CyberDuck). Those who do not have the problem, probably stop waiting for listing, once they receive 226 response. But I do not believe that this is right approach as it's prone to race conditions.
Please contact Wasabi support and ask them to fix their FTP interface.

WinSCP version: latest: 5.13.4 / 8731
OS: Windows 7
Protocol: FTP (but also FTPS)
The problem is very specific and fully reproducible. It only happens handling empty directories on a specific ftp server.
I can provide, of course privately, my account and a temporary password to connect to the server.

PROBLEM DESCRIPTION:

I am using the (relative) new cloud storage provider called WASABI (www.wasabi.com).
The service has a free trial (no credit card, no contract, fully anonymous) of 30 days.
So anyone can open a temporary account and try it.

The cloud storage is organized as "Buckets" -- basically, directories in a filesystem.
After creating your account, you can turn on the option "Access your cloud space via FTP".
The ftp server is: s3.wasabisys.com (to use that, you need to create your buckets choosing region: us-east-1).

Of course, I enabled the FTP server and I connected via WinSCP.
It works perfectly, but there is ONE problem.
WinSCP is unable to handle any EMPTY DIRECTORY in the wasabi cloud space.
I mean: You CANNOT HAVE any empty directory inside your cloud space, otherwise WinSCP aborts the connection.

The error message is quite clear, returned after the unsuccessfully login: "Lost connection. Could not retrieve directory listing. Error listing directory: /yourbucket/emptydir"
Where "emptydir" is an empty directory.

1. If you REMOVE the empty directory from the cloud, WinSCP works without issues with all the other directories.
2. If you use a different ftp client (I used YummyFTP on Mac) you don't have problems handling empty directories.

Attached is the log of the WinSCP connection, using DEBUG2 logging.

Thanks for any support.
Pablo