IPTables

Allow All Incoming HTTP 
   
 
 sudo iptables -A INPUT -p tcp --dport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT 
 sudo iptables -A OUTPUT -p tcp --sport 80 -m conntrack --ctstate ESTABLISHED -j ACCEPT 
 
   
 link: https://www.digitalocean.com/community/tutorials/iptables-essentials-common-firewall-rules-and-commands