注释：
前段时间出现过一种情况，localhost本地登录mysql数据库提示不能连接mysql.sock，第三方工具sqlyog可以登录，具体原因如下。
原创内容如下
mysql.sock的作用
mysql有两种连接方式：
1、TCP/IP
2、socket
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 127
Server version: 5.6.19-log
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> exit
Bye
[root@Wonhigh-Test16 ~]#
mysql.sock的作用是server和client在同一台服务器，并且使用localhost进行链接的时候，就会使用socket来进行连接——仅此而已
也就是：为主机名为localhost建立的MySQL连接，该连接过程通过一个套接字文件mysql.socket实现的。所以该文件被删后，用localhost用户是连接不到MySQL服务器的。
必须建立一条tcp/ip连接，即使用127.0.0.1而不是localhost作为-h的参数去连接MySQL服务器，如：mysqladmin -h 127.0.0.1 -u root -p shutdown，强制地建立一条tcp/ip连接；
关闭MySQL服务器，再重新以localhost为主机名启动MySQL服务器，它就会重新创建一个套接字文件。
对上文加以测试深入了解；
查看mysql.sock具体路径：
[root@Wonhigh-Test16 ~]# ps -ef | grep mysql.sock|grep -v "grep"
mysql 31108 30650 0 Sep10 ? 00:03:17 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/Wonhigh-Test16.err --pid-file=/var/lib/mysql/Wonhigh-Test16.pid --socket=/var/lib/mysql/mysql.sock --port=3306
[root@Wonhigh-Test16 ~]#
mysql 31108 30650 0 Sep10 ? 00:03:17 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/Wonhigh-Test16.err --pid-file=/var/lib/mysql/Wonhigh-Test16.pid --socket=/var/lib/mysql/mysql.sock --port=3306
[root@Wonhigh-Test16 ~]#
转移套接字文件 mysql.sock
[root@Wonhigh-Test16 ~]# mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql1.sock
[root@Wonhigh-Test16 ~]# mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql1.sock
确认本地登录情况
[root@Wonhigh-Test16 ~]# mysql -uroot -p123456
Warning: Using a password on the command line interface can be insecure.
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
[root@Wonhigh-Test16 ~]#
[root@Wonhigh-Test16 ~]# mysql -uroot -p123456
Warning: Using a password on the command line interface can be insecure.
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
[root@Wonhigh-Test16 ~]#
尝试127.0.0.1 tcp/ip连接（第三方工具远程连接都可以‘连接属性会显示为TCP/IP ’）
[root@Wonhigh-Test16 ~]# mysql -uroot -p123456 -h127.0.0.1
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 127
Server version: 5.6.19-log
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
恢复本地连接
[root@Wonhigh-Test16 ~]# mv /var/lib/mysql/mysql1.sock /var/lib/mysql/mysql.sock
[root@Wonhigh-Test16 ~]# mysql -uroot -p123456
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 121
Server version: 5.6.19-log MySQL Community Server (GPL)
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 121
Server version: 5.6.19-log MySQL Community Server (GPL)
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> exit
Bye
[root@Wonhigh-Test16 ~]#
