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.

             Lee