Ignore the class A stuff. What internal IP's are used is mostly arbitrary.
Of course, trying to look smart somewhat backfires when it's obvious you have no clue...
The heartbeats reach the server fine, you don't need to forward an outgoing port. You need to forward 54689, not 30710.
Did I not give him the correct answer? I hardly see how I have no clue.
Also:
Most routers I've used give you an option for protocol and sometimes port translation. Make sure (if they're there) both ports are what you had net_port set to, and the protocol (if it's there) is set to UDP.
Even better, but slightly risky, there may be an option known as DMZ on your router. This makes it so you don't have to forward any ports. You shouldn't use this permanently but for testing it's acceptable. If you can enable DMZ and get the server's heartbeat replies, then you know it's a port forwarding issue. Otherwise it's your router. And don't forget to disable DMZ!
Edit: If possible could you take a screenshot of the port forward configuration page? Censor out any private details etc.