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Unable to connect to SFTP server

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Suresh Gali
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Posts:
1
Location:
USA

Unable to connect to SFTP server

Error
Host is not communicating for more than 15 seconds. Still waiting… Warning: Aborting this operation will close connection!
It was working fine until 09/01/2026

WinSCP log 
. 2026-09-09 11:25:23.301 Looking up host "interface.us.wfs.cloud" for SSH connection
. 2026-09-09 11:25:23.302 Connecting to 158.101.9.121 port 22
. 2026-09-09 11:25:23.342 Connected to 158.101.9.121 (from 10.72.81.15:63114)
. 2026-09-09 11:25:23.385 We claim version: SSH-2.0-WinSCP_release_6.5.7
. 2026-09-09 11:25:23.385 Connected to 158.101.9.121 (from 10.72.81.15:63114)
. 2026-09-09 11:25:23.404 Remote version: SSH-2.0-OpenSSH_7.4
. 2026-09-09 11:25:23.404 We believe remote version has SSH-2 RSA/SHA-2/certificate userauth bug
. 2026-09-09 11:25:23.404 Using SSH protocol version 2
. 2026-09-09 11:25:23.410 Have a known host key of type ssh-ed25519
. 2026-09-09 11:25:39.863 Waiting for data timed out, asking user what to do.
. 2026-09-09 11:25:39.863 Asking user:
. 2026-09-09 11:25:39.863 **Host is not communicating for 15 seconds.
. 2026-09-09 11:25:39.863 
. 2026-09-09 11:25:39.863 Wait for another 15 seconds?** ()
. 2026-09-09 11:25:42.894 Data has arrived, closing query to user.
. 2026-09-09 11:25:42.905 Answer: OK
. 2026-09-09 11:25:42.905 Network error: Software caused connection abort
* 2026-09-09 11:25:42.966 (EFatal) Network error: Software caused connection abort

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JustWebGuy
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Posts:
8

Did you just upgrade to version 6.5.7? I also am having trouble now but can't be sure of what is going on, if it is client-side or server-side. I use 3 clients. The only one that consistently failed is WinSCP.

Login would fail most of the time with:
The server rejected SFTP connection, but it listens for FTP connections.
But if I could log in, then I couldn't actually transfer files:
---------------------------
Error
---------------------------
Network error: Software caused connection abort
---------------------------
OK Cancel Help
---------------------------
I could log in and xfer files with FileZilla, but while connected (thus I know can can connect), WinSCP would not connect.

I rebooted my PC, re-copied the files into my portable folder, tried to connect and it failed. I tried again a couple of times and it worked completely. Closed the app and tried again and could not log in! Tried FileZilla and I could log in.

Where can I get older builds to rule out this new build?

EDIT: I'm thinking maybe FileZilla is just more tolerant or is tolerated by the server or something. It shows disconnects also but still works most of the time. My wonderful (not) host must be having issues.

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JustWebGuy
Joined:
Posts:
8

@martin, is this massive amount of 'session upkeep' normal for an SFTP connection? 
. 2026-09-13 17:14:45.302 Session upkeep
. 2026-09-13 17:14:45.302 Detected network event
. 2026-09-13 17:14:45.321 Session upkeep
. 2026-09-13 17:14:45.790 Session upkeep
. 2026-09-13 17:14:46.288 Session upkeep
. 2026-09-13 17:14:46.790 Session upkeep
. 2026-09-13 17:14:46.790 Received 28 bytes
. 2026-09-13 17:14:47.286 Session upkeep
. 2026-09-13 17:14:47.797 Session upkeep
. 2026-09-13 17:14:48.308 Session upkeep
. 2026-09-13 17:14:48.800 Session upkeep
. 2026-09-13 17:14:49.307 Session upkeep
. 2026-09-13 17:14:49.820 Session upkeep
. 2026-09-13 17:14:50.320 Session upkeep
. 2026-09-13 17:14:50.810 Session upkeep
(And why do the lines start with a period?)

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