On Wed, May 12, 1999 at 10:20:58AM -0500, Wade wrote:
> Duh... That's what I started out thinking, and I let someone convince me
> that 25 was bi-directional and handled both on a LAN. Excuse me while I go
> Snipe hunting. :)
>
> > -----Original Message-----
> > From: Peter van Dijk [mailto:[EMAIL PROTECTED]]
>
> > The users connect thru the dial-up server (which is
> > completely transparent
> > to them) to port 25 on the qmail server to _send_ mail. They get their
> > incoming mail thru POP3 (port 110 on the qmail server).
>
> So do the connections actually go through ports 25 and 110 on the dial-up
> server to connect to ports 25 and 110 on the mail server? I assume the
> dial-up server sees a request to send/receive mail using a certain server
> and then makes the appropriate connections. But since it's transparent to
> the requesting program, does it still have to use the same ports? For some
> reason I've always had trouble understanding the "port" concept. Almost as
> bad a trying to figure out which direction electricity flows in! :)
The dialup-server is just a dumb machine that looks at the destination IP
in the packets your SMTP connection is made of. It forwards these packets
to the correct IP. _that_ IP then starts looking at the port to see what to
do with it.
Ofcourse, if you configure your dial-up machine to allow people only access
to port 25 on the mailserver, the dial-up machine will _look_ at the port
[and throw the packet away if it's not 25 or 110], but it will not actually
_do_ anything with the port. That's still just passed on straight to the
mailserver.
Greetz, Peter
--
| 'He broke my heart, | Peter van Dijk |
I broke his neck' | [EMAIL PROTECTED] |
nognikz - As the sun | Hardbeat@ircnet - #cistron/#linux.nl |
| Hardbeat@undernet - #groningen/#kinkfm/#vdh |
