I added the following line to my firewall script and everything seems to work fine:

$IPTABLES -A INPUT -i $EXTIF (external interface) -m state --state NEW,ESTABLISHED,RELATED -p tcp -s $UNIVERSE (where ever you want to accept connections from) -d $EXTIP (external ip address) --dport 6346 -j ACCEPT

If you have a line for a web server you might try copying it and changing the port.

Best of luck.