Linking on a user port? I thought that was obvious, why it is a bad idea.
Lol, there is nothing bad about it. Services connecting to port 6667 is just as secure as it is connecting on 16667. A port is a port, all 65535 of them are exactly the same although some are reserved for root users only but port 1 is not different than port 65535.
Ports are nothing more than pre-arranged meeting places for servers or servers and clients to meet to establish a connection, nothing more. Ports allow multiple servers and services to use the same IP but listen for different protocols. For example port 80is where you go to see web pages and port 21 is where you go to ftp. Imagine FTPing to port 80, the webserver wouldn't understand your ftp client because it doesn't speak the same protocol as ftp doss and vice versa.
If you want to know more, let's chat in private so we aren't hijacking a thread.
Ciao.