503 bad sequence of commands filezilla client

Hello Folks,

I have a user who is generating the following log in my filezilla server console when trying to access my FTP server using her own filezilla client:

username (ipaddress)> 230 Logged on
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> SYST
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> 215 UNIX emulated by FileZilla
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> FEAT
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> 211-Features:
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  MDTM
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  REST STREAM
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  SIZE
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  MLST type*;size*;modify*;
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  MLSD
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  UTF8
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  CLNT
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)>  MFMT
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> 211 End
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> PWD
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> 257 "/" is current directory.
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> TYPE I
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> 200 Type set to I
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> MLSD
(000304) 10/31/2011 10:09:26 AM - username (ipaddress)> 503 Bad sequence of commands.
(000304) 10/31/2011 10:11:27 AM - username (ipaddress)> 421 Connection timed out.
(000304) 10/31/2011 10:11:27 AM - username (ipaddress)> disconnected.

I don't have any other users running into this problem. Can someone help me understand what settings need changing? Thanks!
Who is Participating?
Gerwin Jansen, EE MVEConnect With a Mentor Topic Advisor Commented:
Can you try changing the FTP mode to PASSIVE on the client side?
Perhaps the client should have sent PASV or PORT first to negotiate the data channel.
The client is should have sent MLST if it wasn't going to do a PASV or PORT first because MLST sends the listing over the control channel but MLSD and LIST use the data channel but the client didnt negotiate a data channel.  Bug in client.
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mrosierAuthor Commented:
Well the client is using the filezilla client in default settings to make the connection with my filezilla server. Should I have her install the latest client version then?
Yes or test with another client program.  Also have her enable the log from her side.
mrosierAuthor Commented:
Thanks! As this person is one of our clients, and we used a third party FTP workaround I don't know if I will be able to get her to troubleshoot with me, but I will give it a try. If I can't get any cooperation in a couple days I will award the points to you for that suggestion. Thanks folks!
Maybe if she does like gerwinjansen suggested and explicitly forces active or passive mode the client will behave.  

If you feel uncomfortable telling someone they have a bug in FileZilla you can always point them to portion of the FTP spec that describes says MLSD should use a data channel:  http://tools.ietf.org/html/rfc3659#page-25
mrosierAuthor Commented:
Well since she has it "out of the box" setup I am pretty certain she has it in passive mode anyway. But as I said, it really can't be troubleshooted anymore until she comes back to me with feedback anyway. And I don't know how likely that is since she got what she needed done. I am not sure how to handle points if she just lets it go rather than solve it ???
mrosierAuthor Commented:
It turns out that It is the firewall of her network that is the issue here. They can't change them for poicy reasons, but they can work around it now. How should I award points here since it is not clear as to the exact problem since we just rerouted our process?
AlexPaceConnect With a Mentor Commented:
Unless the firewall is actively deleting commands sent by the client on the outbound FTP control channel (and leaving other commands intact) then the client is sending an invalid sequence of raw FTP commands.

There are firewalls that actively modify the FTP control channel but they typically do something like modify the outbound PORT command to replace the client's intrnal 192.168.x.x or 10.x.x.x address with a public IP address so the server can open the data channel in Active Mode.  If the firewall was actually at fault in this scenario then it would have to be removing the PORT or PASV command entirely and not replacing it with anything.  So this is behavior on the part of the firewall is definately  technologically possible but seems very unlikely.  On the other hand it also seems unlikley that FileZilla client would screw up in this manner so who knows?!?

I don't really know the etiquette of points but I've seen lots of point splits when multple people contribute.  You didn't end up being able to transfer files but the response that both experts gave identified the client's behavior with regard to the data channel as the cause of the problem rather than anything you needed to change about your server software configuration.  I gave you more information but gerwinjansen responded first and there is value in a quick response.
mrosierAuthor Commented:
The partially ratings are only because I had no way of really following up on the issue with the user having the problem since they were satisfied to use a workaround hence forth. But it is strongly possible the experts' points would have been affective and since they would be probably for others having this problem I am awarding them both points.
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