Open ports in Amazon Linux

Install iptables-services package:

sudo yum install iptables-services -y
systemctl enable iptables
systemctl start iptables

Open port:

# Opening the incoming port.
iptables -I INPUT -p tcp --dport <port> -j ACCEPT
# The command above is for opening the outgoing port.
iptables -I OUTPUT -p tcp --sport <port> -j ACCEPT

Save the rules:

sudo service iptables save