Open flle /etc/sysconfig/iptables:
# vi /etc/sysconfig/iptables
Append rule as follows:
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 3000 -j ACCEPT
Restart iptables service
# service iptables restart
Verify connection on port
netstat -a | grep 3000