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 From:  Lee Sharp <leesharp at hal dash pc dot org>
 To:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] RE: SSH rule dows not work
 Date:  Mon, 10 Sep 2007 10:48:26 -0500
You seem confused about something.  In all TCP 'conversations' there is 
a source and a destination port.  The destination port is set by 
service.  For example, smtp 'listens' on port 25, and ssh 'listens' on 
port 22.  Stations initiating the conversation use a random unused port. 
  For example, a mail server sending you an e-mail will open port 4502 
locally to talk to your port 25.  This is why a firewall has both source 
and destination ports.  You almost never control the source port, so it 
is usually set to any.  The destination port is the service you want.