If you want to open or close a port for a Linux firewall you have to edit the rules in the iptables configuration. By default iptables firewall stores its configuration at /etc/sysconfig/iptables file. You need to edit this file and add rules to open port.
Here are the steps to open the port XY using the default visual editor vi:
Open port XY
Open file /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 XY -j ACCEPT
Save and close the file. Restart iptables:
# /etc/init.d/iptables restart
Verify that port is open
Run following command:
# netstat -tulpn | less
Make sure iptables is allowing port connections:
# iptables -L -n
For more information visit:
http://www.cyberciti.biz/faq/howto-rhel-linux-open-port-using-iptables/
