protocol module ?

[Gregory Nicholls]

 I've been looking at mod-ftpd and mod-pop3 with a view to writing a 
protocol module. What I haven't been able to work out from reading 
these, is how a particular protocol module 'registers' its interest in 
specific connections.
eg. Assume there's 2 protocols being used and we have Listen 8080 http 
and Listen 1234 foo. I use ap_hook_process_connection to insert mod_foo 
into the chain. So far so good but I only want to process connections 
coming on port 1234. Neither mod-ftpd or mod-pop3 seem to have any code 
that examines the connection with a view to declining those they can't 
process. So I'm guessing that there's some mechanism for assigning 
protocols/ports to a specific module. I just don't know how to do it.
      Can some kind soul point out what I've missed please ?
         Thanks,
            Gregory Nicholls