Lost Connection after long time downloading (more than 30/40 minutos). Timeout detected.

Hello,

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.

Do I understand right, that it's a single file that takes so long to download, correct?

Can you download the same file using any other FTP client?

martin wrote:

Do I understand right, that it's a single file that takes so long to download, correct?

Can you download the same file using any other FTP client?

Hello Martin,
Thanks for your response.

1) Yes, only one file is large and takes more time to be transferred.

2) I did the test you asked for. I installed FileZilla and the file was completely downloaded without interruption or login request.

But by analyzing the log, I noticed that the connection is lost during the download (20 minutes later):

"...
2018-07-30 17:45:45 4352 3 Command: RETR VW23x_VL_P7000_I15.vmdk
2018-07-30 17:45:45 4352 3 Response: 150 Opening BINARY mode data connection for VW23x_VL_P7000_I15.vmdk (18601345024 bytes).
2018-07-30 18:05:29 4352 1 Response: 421 Timeout.
2018-07-30 18:05:29 4352 1 Status: Connection closed by server
2018-07-30 18:34:02 4352 3 Response: 226 Transfer complete.
2018-07-30 18:34:02 4352 3 Status: File transfer successful, transferred 18.601.345.024 bytes in 2897 seconds
...
"
The complete log file is attached.

Despite the error, Filezilla does not request a login again and does not lose the download. But I prefer the WinSCP interface.

I've tested several downloads. Always occurs "421 timeout / Connection closed by server" after 20 minutes of transfer via Internet. The problem does not occur on the internal network. I do not know how to solve this. Can you help me?

Thanks in advance.

But in your log file, I see that WinSCP also resumed the transfer after connection was lost.

martin wrote:

But in your log file, I see that WinSCP also resumed the transfer after connection was lost.

Yes, the WinSCP prompts me to retype the password. If I do not log in again, the download is canceled.

But, today I found the option "continue on error (advanced user)" in preferences. I just uncheck it and all worked.

Thank you very much.