setting iptables on centos 6 :
1/ iptables -F
2/ iptables -A INPUT -i lo -j ACCEPT
3/ iptables -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
4/ iptables -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
5/ iptables -A INPUT -p tcp -m tcp --dport 5901 -j ACCEPT
6/ iptables -P OUTPUT ACCEPT
7/ iptables-save | sudo tee /etc/sysconfig/iptables
8/ service iptables restart