iptables best practice for ubuntu 14+ - only 22, 80 and 443 ports

iptables.sh

#This iptables snippet enables port 22, 80 and 443 only.
#WARNING: YOU HAVE TO EXECUTE THE 1ST COMMAND TO AVOID SELF BLOCKING, IF YOU DON'T TYPE THIS COMMAND THEN YOI'LL BE BLOCKED FROM ACCESSING YOUR SERVER.

#Accept active connecion (void self blocking)
iptables -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

#Accept loopback connections
iptables -A INPUT -i lo -j ACCEPT

#Allow port 22 (ssh)
iptables -A INPUT -p tcp --dport 22 -j ACCEPT

#Allow port 80
iptables -A INPUT -p tcp --dport 80 -j ACCEPT

#Allow https
iptables -A INPUT -p tcp --dport 443 -j ACCEPT

#Drop by default
sudo iptables -P INPUT DROP

#Install persistent ipatables (save rules while reboots)
apt install -y iptables-persistent