iptables allow port from code example

Example 1: iptables open port

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

Example 2: iptables block incoming port

iptables -A INPUT -p tcp --dport 8000 -s 1.2.3.4 -j ACCEPT
iptables -A INPUT -p tcp --dport 8000 -j DROP