@dkocher commented

What is the transcript when connecting with Filezilla? Looks like a server issue as it stops responding.

181cba1 commented

Here is the log from Filezilla...

Status:	Resolving address of [serverdomain]
Status:	Connecting to [serverip]…
Status:	Connection established, waiting for welcome message...
Response:	220-Microsoft FTP Service
Response:	220 FTP Server
Command:	USER [user]
Response:	331 Password required for [user].
Command:	PASS ********
Response:	230-FTP Server
Response:	230 User [user] logged in.
Command:	SYST
Response:	215 Windows_NT
Command:	FEAT
Response:	211-FEAT
Response:	    SIZE
Response:	    MDTM
Response:	211 END
Status:	Connected
Status:	Retrieving directory listing...
Command:	PWD
Response:	257 "/[folder]" is current directory.
Command:	TYPE I
Response:	200 Type set to I.
Command:	PASV
Response:	227 Entering Passive Mode ([passivemode]).
Command:	LIST
Response:	125 Data connection already open; Transfer starting.
Response:	226 Transfer complete.
Status:	Directory listing successful

Filezilla seems to work fine.

I have received the same results from from both my work and home computers. Previous versions of Cyberduck logged into the server fine. Immediately after the 3.6.1 upgrade to Cyberduck, FTP stopped working.

@dkocher commented

The compatiblity issue seems to be that the server does not respond to FEAT before we are logged in. The issue was introduced as we are now displaying a message titled The server supports encrypted connections. Do you want to switch to FTP-SSL? if the response to FEAT contains AUTH TLS.

As a workaround disable this feature entering

defaults write ch.sudo.cyberduck connection.unsecure.switch false

in a Terminal.app window.

12b1c10 commented

It appears in the latest release of 3.8.1 this bug is still around.

I see you marked it 3 months ago as thirdparty but the fact that every other FTP client seems to work just fine, I wouldn't say its a third party fix.

Enabling this hidden feature does the trick but unsure why. The Microsoft FTP server I am unsure of the version number. Not sure if it only happens against older versions of IIS or current but it definitely still happens.

As 5138 says to disable this feature all together you can run this above Terminal command but should this be turned into a checkbox in the preferences?

@dkocher commented

The server should return 500 or something but not just close the connection.