Issue with intermittent SFTP connection drops during large file transfers

Hello everyone,

I've been using WinSCP for a while to transfer files over SFTP, but recently I've been running into an issue where the connection randomly drops during larger transfers.

This doesn't happen with small files, but when I try to upload or sync folders with many files or larger sizes, the session sometimes disconnects midway. I then have to reconnect and restart the transfer.

My setup:

WinSCP latest version
SFTP protocol (SSH)
Windows 10
Stable internet connection (no issues in other apps)

What I’ve tried so far:

• Enabling “Keepalives”
  
• Increasing timeout settings
  
• Switching between “Optimize connection buffer size” options
  
• Using both Commander and Explorer interface modes
  

None of these fully solved the issue.

Has anyone experienced something similar? Could this be related to server-side limits, or is there a recommended configuration in WinSCP for more stable large transfers?

Any advice or suggestions would be greatly appreciated.
Thank you in advance!

It's possible for it to be networking related firmware or drivers. Those do normally update and can cause problems from bugs and lack of testing. Problems there can be very tricky and be difficult to narrow down to.

SFTP, FTP, etc are really stable with many many years behind them.

There's possibilities, like config being off, but networking and related is extremely likely to show up as a problem as its critical to it working well.

I'd suggest Martin seeing a log and seeing if anything can be seen that way.

If Martin can't find anything, a quick shortcut is to try another SFTP software, computer, router, internet if possible, etc. Narrow down to the piece of the puzzle then further from there.

Please attach a full session log file showing the problem (using the latest version of WinSCP).