Thank you very much

@gstadter: Yes it does. See the discussion above.
And the documentation:
https://winscp.net/eng/docs/ui_login_ftp

I'm using SolarWinds Serv-U managed FTP server and would like to use virtual hosts....hence wondering if WinSCP can leverage the HOST command

OK, I have implemented optional use of HOST command.

I have sent you an email with a development version of WinSCP to address you have used to register on this forum.

I can't think of a reason for pre-login commands other than HOST.

For what it's worth, here are screenshots from FTP Voyager and Beyond Compare which shows how they implemented an on/off option for the HOST command:

FTP Voyager:
https://public.dm2302.livefilestore.com/y2pFJFXNk3jfoRzKEbDqQUOrqyhmLmt_742xYDP8AVCHITTasDSQFprwf8IK7CX_hLHOP-1Waj1cuSOIQoVuCCDz2SyzAxi6ZKrk9zO464SKVs/FtpVoyager8.png

Beyond Compare:
https://public.dm2302.livefilestore.com/y2p7sX6fOPQEwwcOE7BqwPdhgKWe7e8XQSYiSKxzuJLpB64K-S54MFpJL6mpW5k6y-l8t-PPrzJZQi2XRDwepAiK2j1yviteazTVb6-NVBsR_c/BeyondCompare8.png

Thanks!

Thanks for your suggestion. Do you know of any other use for "pre-login" commands, apart from HOST?

Just a thought, but what a few FTP clients have been doing is adding an option to send the HOST command before logging in, or providing support for sending custom pre-login commands. For example, in WinSCP's Advanced Site Settings, you could modify the Protocol Options page to add another text box for pre-login commands, or add you could an On/Off option to send a HOST command before logging in.

It's more difficult to implement that I original hoped. This requires FEAT command to be send before authentication, so that HOST support is detected.

This request has been added to the tracker:
https://winscp.net/tracker/1166

Sure, I can set up an FTP site for you for testing; I'll send you a private email so we can set that up.

FYI, the following blog post has a list of the FTP servers and clients which currently support the new FTP HOST command:
https://learn.microsoft.com/en-us/archive/blogs/robert_mcmurray/rfc-7151-file-transfer-protocol-host-command-for-virtual-hosts

Thanks!

Do you have a server that supports this, that I can use to test this against?

Now that RFC 7151 has been published, (which defines the FTP HOST command), can WinSCP add support for it?

See https://datatracker.ietf.org/doc/html/rfc7151 for details.

Thanks!