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 _______________________________________________ LARTC mailing list / [EMAIL PROTECTED] http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
