Linux: Iptables Allow MYSQL server incoming request on port 3306

Open port 3306

In most cases following simple rule opens TCP port 3306:
iptables -A INPUT -i eth0 -p tcp -m tcp --dport 3306 -j ACCEPT

Reference: http://www.cyberciti.biz/tips/linux-iptables-18-allow-mysql-server-incoming-request.html