Topic "0kb Transfer Issue"

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Joined: 2015-05-28
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Currently having some issues while using WinSCP 5.7 on Windows XP which seem to be a new occurrence in the past month.

The issue occurs both in command line and GUI modes, with the command line being used both manually and as part of a script.

I'm using a scheduled .bat file in order to automate nightly downloads of new files from a server which we can only access via SFTP due to firewall requirements. This initially seemed to work correctly but over the last couple of days I've noticed a tendency for certain files to fail during download. In command line mode this results in the file being skipped and creating a 0kb named version of the file on the local system, in GUI mode this asks the user for prompt and will then correctly download the file once I click retry.

I believe this also relates to an issue occasionally occurring during browsing of the remote server which I have not logged, in which I receive an error message stating "Could not retrieve directory listing, Cannot open data connection". This again occurs once and then if the action is repeated the directory structure will be accessed and displayed.

I've uploaded a zip file of my script files and logs from all 3 debug modes privately. The logs are from separate recreations of the issue and so the files which fail may or may not be the same.

Any help with this matter is greatly appreciated, it's entirely possible this is actually a server based issue but I'm hoping you'll be able to point me in the rough direction of which server settings could cause this behaviour if this is the case


Giles Dash

Giles Dash (85.53 KB) Private file

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Joined: 2002-12-10
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Location: Prague, Czechia
The server occasionally responds to PASV command with "425 Cannot open data connection".
I have no idea why this is happening. Note that the server is not connecting anywhere, it is just opening a listening port in this phase. Such operation can hardly fail. Maybe except for a case the server runs our of free port numbers.
Did you check a server-side log?

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