SSH2_MSG_CHANNEL_DATA error when overwriting files

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yggdrasil
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SSH2_MSG_CHANNEL_DATA error when overwriting files

Greetings,

I am getting the error "SSH2_MSG_CHANNEL_DATA" when trying to overwrite a file in any directory on our SFTP server. New file uploads work as expected. I'm trying to determine the difference being sent to our SFTP server for file overwrites as opposed to new file uploads.

Notes:
Only occurs with WinSCP overwriting files to SFTP.
Occurs in previous version of WinSCP and current. (sorry don't have the exact previous version but was fairly recent)
FileZilla SFTP, Linux SFTP, Web Dashboard HTTPS, all work without issue.

Options tried so far with all settings (enabled and disabled for most):
Preserve Timestamp
Set permissions
Ignore permission errors
Transfer mode (text and binary)
Enable queue processing
Use multiple connections for single transfer
Transfer resume
Optimize connection buffer size

WinSCP log:
< 2023-10-20 08:27:33.348 Type: SSH_FXP_STATUS, Size: 48, Number: 7430
< 2023-10-20 08:27:33.348 65,00,00,1D,06,00,00,00,08,00,00,00,1F,55,6E,73,75,70,70,6F,72,74,65,64,20,
< 2023-10-20 08:27:33.348 6F,70,65,72,61,74,69,6F,6E,20,72,65,71,75,65,73,74,65,64,00,00,00,00,
< 2023-10-20 08:27:33.348 Status code: 8, Message: 7430, Server: Unsupported operation requested, Language:
. 2023-10-20 08:27:33.348 Waiting for another 4 bytes
. 2023-10-20 08:27:33.348 Looking for incoming data
. 2023-10-20 08:27:33.348 Looking for network events
. 2023-10-20 08:27:33.351 Received SSH2_MSG_CHANNEL_DATA for nonexistent channel 0
. 2023-10-20 08:27:33.351 Attempt to close connection due to fatal exception:
* 2023-10-20 08:27:33.351 Received SSH2_MSG_CHANNEL_DATA for nonexistent channel 0
. 2023-10-20 08:27:33.351 Closing connection.
. 2023-10-20 08:27:33.351 Selecting events 0 for socket 2192
. 2023-10-20 08:27:33.351 Fatal error while disposing the SFTP queue.
SFTP server log:
#09 z30 <0> (373947241698677928434) ------ Handling event type SftpserverFileWriteEventArgs ------
#09 z60 <0> (373947241698677928434) FileWriteRequestHandler: Received file write request for handle 101; Offset=850304
#09 z10 <0> (373947241698677928434) FileWriteRequestHandler: Specified offset does not match written bytes; possible out-of-order write request
#13 z30 <0> (373947241698677928434) Log message from server: Disconnected: [11]
Any help would be appreciated. Thanks!

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martin
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martin avatar
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40,278
Location:
Prague, Czechia

Re: File attached as private

The server seems to fail a random write request. So it does not look like WinSCP is sending something wrong. You will have to investigate server-side logs to see what the server thinks the problem is.
You might also try setting SFTP protocol version to 3:
https://winscp.net/eng/docs/ui_login_sftp
Or reducing transfer speed.

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yggdrasil

Protocol version 3 worked!

Hey Martin – switching to protocol version 3 worked! We have been working with the server software's support team for weeks going over server logs but nothing has worked until now.

Thank you!

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