1. Definitely focus on getting it to work on "localhost" first.
2. I assume this is probably a TCP port (rather than UDP). If so, you can use "telnet localhost PORT#" to check connectivity. Taking a wireshark trace might also be helpful.
3. Yes, your firewall/iptables is definitely the first thing to look at.
Perhaps SELinux might be the second thing to look at.
4. In any case, these links might help:
Please post back what you find!