Server unexpectedly closed network connection

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cecilia.schultz1@gmail.com
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Server unexpectedly closed network connection

Version 5.19.2 Build 11614
Windows 10.
Get "Server unexpectedly closed network connection" when trying to connect to a given SFTP (port 22) server from computer A.
Tested form other computers (e.g. computer B), I can connect fine.
Our network team has confirmed they do not block outbound traffic. Also, I have myself done a telnet port test to the given site on port 22, and it looks fine.
The destination SFTP server admin says they do not whitelist, and no changes have occurred recently.
Attached are the 2 logs (the one from my computer, showing error, and the one from computer B, no issues). Please advise.
  • from.computerA.ERROR.winscp.log (4.42 KB, Private file)

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cecilia.schultz1@gmail.com
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RE: Server unexpectedly close network connection

Attached is the other log, from the other computer, which can connect to the same site, with the same credentials, with no issues.
  • from.computerB.OK.winscp.log (36.19 KB, Private file)

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martin
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Re: Server unexpectedly closed network connection

Can you connect with any other SFTP/SSH client?

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cecilia.schultz1@gmail.com
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Re: Server unexpectedly closed network connection

Martin, Thank you for responding. I tried with FileZilla a couple of days ago, and it also failed with error "Could not connect to server". Now when I try to run FileZilla, it gives me an error "an error occurred loading the transfer queue from c:\users\.. Some queue items might not have been restored."
What other SFTP client can I use?
Here's a recap of the problem, and what we have found so far:
1) the error happens even before entering the password.
2) The error happens only from computer A. I have tried (with same WinSCP version) SFTP connection from other computer and it worked fine.
3) WinSCP SFTP connection to other SFTP servers, from computer A, is fine.

4) I was able to connect to this SFTP server before (last time I successfully connected was 9/22)

5) does not appear to be a firewall issue:
Telnet port 22 test did not get any errors. Also, network admin on external site showed my attempt with traffic on 22 was allowed. However, it also showed another traffic on port 21 was denied. I found a default setting in WinSCP ("Knock FTP port") that apparently attempts to use port 21 when port 22 fails.
This hints that for some reason the SFTP server had an issue with this connection.

I don't know if this may help, but from the other computer where I can connect, I can see the host key fingerprint ("Generate session URL/code") It looks like "ssh-rsa 1024 ..."

Thank you
Cecilia

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cecilia.schultz1@gmail.com
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Re: Server unexpectedly closed network connection

I was able to download Progress_WSFTP (formerly Ipswitch) and it failed to given server.
(previously I tried to connect to a different SFTP server and it worked, so it is only to this certain SFTP server, and only from my computer)
Finding Host sftp.ocde.us ...
[2021.10.12 09:16:45.609] Connecting to 209.79.64.100:22
[2021.10.12 09:16:45.612] Connected to 209.79.64.100:22 in 0.002714 seconds, Waiting for Server Response
[2021.10.12 09:16:45.614] Server Welcome: 
[2021.10.12 09:16:45.614] SSH Transport closed

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cecilia.schultz1@gmail.com
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Re: Server unexpectedly closed network connection

The issue was solved.
I uninstalled WinSCP, and selected to clean up any and all cache, sites, configuration. This time it installed WinSCP 5.19.3 (just a couple of days ago the latest was 5.19.2?).
This time, it prompted to add the host key to the cache. Then tried, and it worked.
Thank you.

** I need to make a somewhat unrelated request here, because I haven't been able to locate a customer support to help with my login to the WinSCP forum. I have an account that I created sometime ago, that has my work email (schultz_cecilia@rsccd.edu), however I don't remember the password, nor the username. The login only has an option of "forgot password", and it requires me to enter the username (which I don't remember), so I was forced to create another login (under my personal email). Could you please let me know my username (for my work email) so I can reset the password? Thanks!!

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martin
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Re: Server unexpectedly closed network connection

cecilia.schultz1@gmail.com wrote:

The issue was solved.
...
Isn't just coincidence? I cannot imagine that 5.19.2 cannot connect, but 5.19.3 can. Can you now connect with the other clients?

Could you please let me know my username (for my work email) so I can reset the password? Thanks!!
It's ceciliaschultz.

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