Port 3306 is Configured in Firewall

https://mariadb.com/kb/en/library/configuring-mariadb-for-remote-client-access/

linux 포트 설정

firewall-cmd --add-port=3306/tcp 
firewall-cmd --permanent --add-port=3306/tcp

ufw allow 3306과 완전히 같은 것인가?..