[Web4lib] Re: is FTP with a browser really FTP

[Peter Murray]

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I suspect it is the difference between FTP's PORT and PASV modes.   
Here is an extract from http://support.microsoft.com/kb/323446

   FTP supports two modes. These modes are called Standard (or PORT
   or Active) and Passive (or PASV)....

   Standard mode FTP clients first establish a connection to TCP
   port 21 on the FTP server. This connection establishes the FTP
   command channel. The client sends a PORT command over the FTP
   command channel when the FTP client needs to send or receive
   data, such as a folder list or file. The PORT command contains
   information about which port the FTP client receives the data
   connection on....

   Passive mode FTP clients also start by establishing a connection
   to TCP port 21 on the FTP server to create the control channel.
   When the client sends a PASV command over the command channel,
   the FTP server opens an ephemeral port (between 1024 and 5000) and
   informs the FTP client to connect to that port before requesting
   data transfer....

I don't have immediate access to a Windows box, but in GNU/Linux one  
can typically use the ftp command "passive on" to switch to PASV mode.


Peter

On Jul 7, 2008, at 11:41 AM, John Fitzgibbon wrote:
> I work from behind a firewall. FTP from the command line is blocked.  
> However, if I open an FTP session with my browser by typing ftp://  
> for the protocol it works unhindered by the firewall.
>
> Does Internet Explorer 7 process FTP requests through HTTP or is  
> there something else going on?

- --
Peter Murray                            http://www.pandc.org/peter/work/
Assistant Director, New Service Development  tel:+1-614-728-3600;ext=338
OhioLINK: the Ohio Library and Information Network        Columbus, Ohio
The Disruptive Library Technology Jester                http://dltj.org/
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