Ahh, I think there is a misconception on what passive FTP actually does.
Here is a link to (some class's notes) on ftp. Check out section 2.1
(Passive Versus Active Mode FTP)
http://bigworm.colorado.edu/Saclass/class14.html
So, as you see, passive mode does not use only one connection. It still
uses two. The only difference between passive and active is which machine
(the client or the server, respectively) is initiating the connection.
Thus, /only/ passive FTP will work when the client is behind a "one-to-many"
NAT box (such as IPmasquerading). This is because the client initiates a
connection to the server. When you are doing one-to-many NAT, outgoing
connections work fine, but incoming connections must have a
"port-forwarding" set up (or intelligence in the NAT box), so that an
incoming connection (to the single Internet-routable address in use) can be
properly forwarded to the (non-routable internal address of the) internal
machine.
Thus, if your FTP server is behind a NAT box, you need /it/ to initiate the
connection (I.E. active mode). Otherwise, you can't get a connection /to/
the FTP server (since it is coming in on an unpredictable port). This also
applies to FTP servers behind firewalls that only permit outgoing
connections by default.
This is why I want a /1/ port file transfer program. FTP is not a 1 port
file transfer program. I'm looking for something that does control /and/
data over the same connection.
Thanks,
Jordan
----- Original Message -----
From: "Adam Tauno Williams" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, March 05, 2001 1:24 PM
Subject: Re: Single Port File transfer
> >Well, how do use HTTP to copy files to the machine I am controlling? I
> >have had people tell me that this is possible, but I guess I've never
really
> >investigated. If it involves writing ASP (or whatever) and submitting
files
> >via the browser, this is not so much what I am looking for.
>
> No matter what your going to have to run a "client" on the machine you are
> controlling, browsers are ubiquitous. You shouldn't need to write any
scripts,
> just make the file on your machine available via the web server.
>
> >As far as using FTP in passive mode, can you tell me how to get this to
> >work when both machines are behind a "one-to-many" NAT? I was pretty
sure
> >the FTP protocol required 2 connections, one for control and one for
data.
> >Is this not right?
>
> Passive FTP uses one port, "standard" ftp uses two. The point of passive
FTP is
> that it works through firewalls, ip masq, NAT, whatever. If you do an FTP
> download in most web browsers (Netscape at least) it is done in passive
mode.
>
> Systems and Network Administrator
> Morrison Industries
> 1825 Monroe Ave NW.
> Grand Rapids, MI. 49505
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