I'm researching the possibilities of an FTP Proxy that can act as an authentication plugin of an FTP server. As a side product, I experienced totally different FTP dialects from popular FTP clients.
FileZilla 3.3.2.1
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> Connected, sending welcome message...
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> 220-FileZilla Server version 0.9.34 beta
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> 220-written by Tim Kosse (Tim.Kosse@gmx.de)
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> 220 Please visit http://sourceforge.net/projects/filezilla/
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> USER zhao
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> 331 Password required for zhao
(000001) 13/04/2010 9:54:18 AM - (not logged in) (127.0.0.1)> PASS ********
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 230 Logged on
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> SYST
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 215 UNIX emulated by FileZilla
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> FEAT
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 211-Features:
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> MDTM
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> REST STREAM
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> SIZE
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> MLST type*;size*;modify*;
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> MLSD
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> UTF8
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> CLNT
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> MFMT
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 211 End
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> PWD
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 257 "/" is current directory.
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> TYPE I
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 200 Type set to I
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> PASV
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 227 Entering Passive Mode (127,0,0,1,4,27)
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> MLSD
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 150 Connection accepted
(000001) 13/04/2010 9:54:18 AM - zhao (127.0.0.1)> 226 Transfer OK
Firefox 3.6.3
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> Connected, sending welcome message...
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> 220-FileZilla Server version 0.9.34 beta
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> 220-written by Tim Kosse (Tim.Kosse@gmx.de)
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> 220 Please visit http://sourceforge.net/projects/filezilla/
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> USER zhao
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> 331 Password required for zhao
(000002) 13/04/2010 9:59:59 AM - (not logged in) (127.0.0.1)> PASS ********
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 230 Logged on
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> SYST
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 215 UNIX emulated by FileZilla
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> PWD
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 257 "/" is current directory.
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> TYPE I
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 200 Type set to I
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> PASV
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 227 Entering Passive Mode (127,0,0,1,4,218)
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> SIZE /
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 550 File not found
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> MDTM /
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 550 File not found
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> RETR /
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 550 File not found
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> PASV
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 227 Entering Passive Mode (127,0,0,1,4,220)
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> CWD /
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 250 CWD successful. "/" is current directory.
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> LIST
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 150 Connection accepted
(000002) 13/04/2010 9:59:59 AM - zhao (127.0.0.1)> 226 Transfer OK
IE 8
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> Connected, sending welcome message...
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> 220-FileZilla Server version 0.9.34 beta
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> 220-written by Tim Kosse (Tim.Kosse@gmx.de)
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> 220 Please visit http://sourceforge.net/projects/filezilla/
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> USER zhao
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> 331 Password required for zhao
(000003) 13/04/2010 10:01:42 AM - (not logged in) (127.0.0.1)> PASS ********
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> 230 Logged on
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> CWD /
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> 250 CWD successful. "/" is current directory.
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> TYPE A
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> 200 Type set to A
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> PASV
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> 227 Entering Passive Mode (127,0,0,1,4,226)
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> LIST
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> 150 Connection accepted
(000003) 13/04/2010 10:01:42 AM - zhao (127.0.0.1)> 226 Transfer OK
It looks that Firefox has the ugliest commands, right?