Ubuntu 18.04 msyql远程连接失败原因

1. 端口未开放
   用sudo ufw allow mysql开放3306端口
2. 配置问题
   把/etc/mysql/mysql.conf.d/mysqld.cnf的bind-address = 127.0.0.1注释掉
3. user未设置远程访问
   grant all privileges on *.* to 用户名@'%' identified by '密码';