LINUX can open network ports that allow external access through the following commands:
/sbin/iptables -I INPUT -p tcp --dport 8000 -j ACCEPT #Open port 8000
/etc/rc.d/init.d/iptables save #Save Configure
/etc/rc.d/init.d/iptables restart #Restart the service
to see if the port is open
/etc/init.d/iptables status