RE: Active vs passive FTP

["SIMS, KEN" <KSIMS@xxxxxxxxxxxxxxxx>]

Hi Jim -

>Date: Mon, 29 Nov 1999 16:17:39 -0800
>From: Jim Langston <jlangston@conexfreight.com>
>Subject: Re: Ethernet x-over cable
>
>Hmm?  Please explain the difference between active
>and passive modes of FTP.  I wrote an FTP client a few
>years back on a PC in Delphi just to do it.  I got it working,
>then abandoned it, I just wanted to see how it was done.

I'll jump in here since I had to deal with this recently for a firewall on
my PC at home.  As I understand, active vs passive only applies on gets,
basically just file gets and directory lists.

In both cases, the client sends the request to the server on port 21.

In active mode, the server then initiates a data connection to the client to
send the actual file data or directory listing.  This is done on a port of
1024 or higher.  If there is a firewall set to reject connections initiated
by the other end, this is a problem.

In passive mode, the client initiates the data connection to the server.
This is done on port 20.

For file puts, the client always initiates the data connection.

Ken
Southern Wine and Spirits of Nevada, Inc.
Opinions expressed do not represent those of my employer or anyone else.

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