No, the server is only using a single port - the one it's listening to. It's also already standard to run multiple, local relays per server instance in the case

No, the server is only using a single port - the one it's listening to. It's also already standard to run multiple, local relays per server instance in the case of IRCds. Many servers run multiple instances that together span 3 or 4 ports; 6667, 6668, 6669 etc.