The MySQL Connectors and APIs are the drivers and libraries that you use to connect applications in different programming languages to MySQL database servers. The application and database server can be on the same machine, or communicate across the network.
执行mysql指令进入MySQL数据库时：
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
启动MySQL服务时：
[root@VM_0_10_centos support-files]# ./mysql.server start
Starting MySQL.... ERROR! The server quit without updating PID file (/usr/local/mysql/data/VM_0_10_centos.pid).
查看VM_0_10_centos.err日志文件，发现如下错误信息：
2019-04-13T06:07:59.371987Z 0 [ERROR] [MY-010262] [Server] Can't start server: Bind on TCP/IP port: Address already in use
2019-04-13T06:07:59.371999Z 0 [ERROR] [MY-010257] [Server] Do you already have another mysqld server running on port: 3306 ?
2019-04-13T06:07:59.372253Z 0 [ERROR] [MY-010119] [Server] Aborting
2019-04-13T06:08:01.120673Z 0 [System] [MY-010910] [Server] /usr/local/mysql/bin/mysqld: Shutdown complete (mysqld 8.0.15) MySQL Community Server - GPL.
执行/etc/init.d/mysql.server status 时：
[root@VM_0_10_centos support-files]# ./mysql.server start
Starting MySQL..... ERROR! The server quit without updating PID file(/usr/local/mysql/data/VM_0_10_centos.pid).
[root@VM_0_10_centos mysql]# /etc/init.d/mysql.server status
ERROR! MySQL is not running, but lock file (/var/lock/subsys/mysql) exists
[root@VM_0_10_centos mysql]# netstat -apn | grep 3306
tcp6 0 0 :::3306 :::* LISTEN 1117/mysqld
[root@VM_0_10_centos mysql]# kill -9 1117
[root@VM_0_10_centos mysql]# /etc/init.d/mysql.server start
Starting MySQL.. SUCCESS!
alter user 'root'@'localhost' identified by '新密码'
参考链接：https://geeksterminal.com/another-mysqld-server-running-port-3306/1681/