GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'YOUR PASSWORD';
sudo iptables -A INPUT -i YOUR_NETCARD_INTERFACE(e.g. eth0) -p tcp --destination-port 3306 -j ACCEPT
sudo vim /etc/mysql/my.cnf
modify bind-address = 0.0.0.0
sudo /etc/init.d/mysql restart
it's DONE