Make sure MySQL binds to 0.0.0.0 and not 127.0.0.1 or it will not be accessible from outside the machine
You can ensure this by editing the /etc/mysql/my.conf file and looking for the bind-address item–you want it to look like bind-address = 0.0.0.0. Then save this and restart MySQL:
sudo service mysql restart
If you are doing this on a production server, you want to be aware of the security implications, discussed here: https://serverfault.com/questions/257513/how-bad-is-setting-mysqls-bind-address-to-0-0-0-0