SCOUG-Programming Mailing List Archives

<< Previous Message << >> Next Message >>

Date:	Fri, 2 Oct 1998 12:45:22 PDT
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: FTP server - po

Content Type: text/plain

Emerson, Tom # GPS-MDI wrote:
>
> a single SOCKET (or PORT) is the combination of THREE actual addresses:
>
> The ransport address: 20
> The etwork address: 204.125.16.99 [which defines an arbitrary
> computer on, say, abc.net]
> The ata-link address: 00-40-80-12-34-56 [the hard-coded actual
> address of the NIC in joe's computer]
> (technically, the

hysical and the ata-link layers are combined
> for the purposes of defining an address)

Is your address contained in each packet's header? If so, where?

> packets from joe to you would look like:
>
> 98-00-12-45-78-45 / 00-40-80-12-34-56 / 129.129.0.15 / 204.125.16.99 / 20
>
> while packets from fred to you look like:
>
> 98-00-12-45-78-45 / 00-40-80-99-88-77 / 129.129.0.15 / 18.0.1.200 / 20

You didn't say what these five numbers are. What are they?

> > I'm really confused now. I thought the FTP server (the parent process)
> > was listening on port 20. How does the TCP stack know to give the
> > packet that comes in on port 20 to the child process? In the header,
> > the IP address is the same and both carry the same port number, 20.
> > There's no other identification in the header that the TCP stack can
> use
> > to properly steer the packet.
>
> the packets DO have different addresses for the target

Which number is the target value? And which layer contains the table
that has the matching target value so the packet can be properly steered
to the target?

Thanks.

- Peter Skye

=====================================================

To unsubscribe from this list, send an email message
to "steward@scoug.com". In the body of the message,
put the command "unsubscribe scoug-programming".

For problems, contact the list owner at
"rollin@scoug.com".

=====================================================

Return to [ 02 | October | 1998 ]

SCOUG, Warp Expo West, and Warpfest are trademarks of the Southern California OS/2 User Group. OS/2, Workplace Shell, and IBM are registered trademarks of International Business Machines Corporation. All other trademarks remain the property of their respective owners.