Open MySQL Port 3306 in CentOS 7
To allow MySQL to connect from remote server on CentOS 7 server, you need to enable port 3306 in firewall.
To do this, edit file
vi /etc/sysconfig/iptables
Find
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
Add above
-A INPUT -p tcp -m state --state NEW -m tcp --dport 3306 -j ACCEPT
Restart server.