Keep FTP open (as in WinSCP)

DOpus provides some configuration to keep the FTP connection alive, like "Keep link alive" in Network -> Reconnect.

Although that option is enabled for the FTP connection I've configured, the connection is still lost after a short time and DOpus has to reconnect (auto-reconnect is enabled) and takes some time to change directory.

I mention WinSCP since it is the only software I tested that can keep the connection open, I mean, after some idle time, you can browse to other folders in the FTP server without reconnecting. In my case WinSCP and DOpus seem to be configured in the same way (keep alive option and a 30 s delay).

Could it be possible for DOpus to act like WinSCP in this regard or do you know which are the differences?

Thanks.

The SCP and FTP protocols are different. If you have set the option, Opus will attempt to keep the connection alive by sending NOPs but many FTP servers simple ignore this and will drop the connection after a period of non transfer activity so as to make the sockets available for other users.

But the connection is configured in WinSCP as an FTP connection (port 21), it is not using a secure connection or scp protocol.

In this particular case, shouldn't WinSCP and DOPus behave in the same way?

It might be keeping the connection alive via a different method (e.g. changing directories or listing the directory every so often might fool a server into keeping it alive when the server tries to avoid it).

Opus only uses the 'official' way to keep a server alive, which some servers choose to ignore on purpose. Whether it's right to bypass the server's wishes is up for debate.

If you look at the FTP logs in both programs they should be able to tell you exactly which commands are being sent, for a fuller picture. There is a Debug option in Opus which makes the log show more information. (Set the FAQs linked in my signature for the FTP FAQ with details on how to find the log and debug option.)

Thanks, I hadn't thought in enabling the log. Now I can see the differences:

[ul]
[li]DOpus is sending a NOOP command. But after a while, the server closes the connection with "No transfer timeout (600 seconds): closing control connection" error.[/li]
[li]WinSCP is sending other commands like TYPE I, TYPE A, PWD, PASV, MLSD and REST 0 in a random pattern.[/li][/ul]
That seems to be the trick that WinSCP is using to bypass the timeout and keep the connection alive.