Check on the ePO server: it's only the listening device that needs to avoid a port conflict.
Bear in mind that if you're going to use agent handlers, these will also need to listen on this port, so you need to choose a port that is free on the ePO server and all AH machines.
Thanks Joe for clearing my doubt. I was a bit confused if the clients would also listen to the secure port.
Nope, the only ports that the agent listens on are the agent wakeup port (8081 by default ) and the superagent wakeup port (8082 by default, but only if the machine is configured as a superagent.)
Both of these can be configured by policy as well.