iptables add tcp port code example

Example 1: iptables open port

sudo iptables -A INPUT -p tcp --dport xxxx -j ACCEPT

Example 2: iptables allow port from anywhere

sudo iptables -A INPUT -p tcp --dport 443 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
sudo iptables -A OUTPUT -p tcp --sport 443 -m conntrack --ctstate ESTABLISHED -j ACCEPT