From: James Sneeringer <james+lartc@vincentsystems.com>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] why dont packets go where i want?
Date: Thu, 17 Oct 2002 16:00:26 +0000 [thread overview]
Message-ID: <marc-lartc-103487049623012@msgid-missing> (raw)
In-Reply-To: <marc-lartc-103484229426470@msgid-missing>
On Thu, Oct 17, 2002 at 11:44:13AM +0200, Francois Dessart wrote:
> ftp-data 20/tcp
> ftp-data 20/udp
> ftp 21/tcp
> ftp 21/udp
> FTP data (passive) use port 20.
This is incorrect.
Both standard and passive FTP use tcp/21 as a control channel (logins,
commands, etc.).
Standard FTP uses tcp/20 as the server's source port for data transfers.
Prior to a transfer, the client listens on an arbitrary port and instructs
the server to connect to it for the transfer.
Passive FTP does not use tcp/20 at all. Instead of the server connecting
to the client, the client connects to the server for data transfers. The
server chooses an arbitrary port for the client to connect to. The intent
of passive FTP was to work around firewalls that don't permit inbound
connections.
-James
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next prev parent reply other threads:[~2002-10-17 16:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-17 8:09 [LARTC] why dont packets go where i want? Kertész Viktor
2002-10-17 8:36 ` Francois Dessart
2002-10-17 8:38 ` Francois Dessart
2002-10-17 9:01 ` Kertész Viktor
2002-10-17 9:09 ` Walter Haidinger
2002-10-17 9:29 ` Kertész Viktor
2002-10-17 9:44 ` Francois Dessart
2002-10-17 10:02 ` Walter Haidinger
2002-10-17 10:26 ` Kertész Viktor
2002-10-17 10:44 ` Stef Coene
2002-10-17 11:01 ` Walter Haidinger
2002-10-17 12:16 ` Kertész Viktor
2002-10-17 13:20 ` Walter Haidinger
2002-10-17 13:25 ` Michael T. Babcock
2002-10-17 16:00 ` James Sneeringer [this message]
2002-10-17 20:04 ` Walter Haidinger
2002-10-18 6:21 ` Francois Dessart
2002-10-18 6:41 ` Stef Coene
2002-10-18 17:42 ` James Sneeringer
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