I'm using WinSCP 5.13.3 (Build 8565) with the vsFTPd (3.0.3) server on a Linux Mint 18.
For WAN connections (internet), I use passive mode.
For LAN connections, I use PORT/ACTIVE mode.
File protocol: FTP (no encryption)
Everything was good, logins, listing files, downloads and uploads. But, when I try to download large files that takes over 35/40 minutes, at the end of the transfer, the WinSCP shows 99%, "Time left" 0:00:00 and "Time elapsed" runs more 15 seconds. Afther this time, I receive the error message:
"Lost connection" (on tray icon).
then I receive the message:
"Timeout detected. (control connection)
copying files from remote side failed."
This problem occurs when the connection is from internet (passive mode) and the
downloads last more than 35/40 minutes.
On local connections (port/active mode) and with downloads
downloads that take less time, this problem does not occur.
Follow attached the files WinSCP.log and the vsFTPd.log, log files of an example transfer of a file containing 5 files, totaling 11.1 GB (11,986,940,343 Bytes)
I do not use standard ports for FTP connections.
In my internet router, the Linux server is on a DMZ zone.
The linux firewall was configured to accept connections from ports:
2150 FTP connections
2050 FTP Data
21500-21600 passive ports.
Greetings from Brazil!
Sorry my English.