不加127.0.0.1时，默认连接使用socket协议:
[apps@mvxl2972 ~]$ mysql -ulmsapps -pLms166apps
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 35
Server version: 10.1.12-MariaDB MariaDB Server

Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> \s
--------------
mysql Ver 15.1 Distrib 10.1.12-MariaDB, for Linux (x86_64) using readline 5.1

Connection id: 35
Current database:
Current user: lmsapps@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server: MariaDB
Server version: 10.1.12-MariaDB MariaDB Server
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: utf8
Db characterset: utf8
Client characterset: utf8
Conn. characterset: utf8
UNIX socket: /tmp/mysql3306.sock
Uptime: 1 day 22 hours 14 min 54 sec

Threads: 2 Questions: 72 Slow queries: 0 Opens: 0 Flush tables: 1 Open tables: 11 Queries per second avg: 0.000

加localhost连接使用socket协议:
[apps@mvxl2972 ~]$ mysql -ulmsapps -pLms166apps -h localhost
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 59
Server version: 10.1.12-MariaDB MariaDB Server

Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> \s
--------------
mysql Ver 15.1 Distrib 10.1.12-MariaDB, for Linux (x86_64) using readline 5.1

Connection id: 59
Current database:
Current user: lmsapps@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server: MariaDB
Server version: 10.1.12-MariaDB MariaDB Server
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: utf8
Db characterset: utf8
Client characterset: utf8
Conn. characterset: utf8
UNIX socket: /tmp/mysql3306.sock
Uptime: 1 day 22 hours 26 min 16 sec

Threads: 4 Questions: 371 Slow queries: 0 Opens: 0 Flush tables: 1 Open tables: 11 Queries per second avg: 0.002

2.在skip_name_resolve为停用状态下：
更改配置文件中skip_name_resolve为off，并重启mysql.
MariaDB [(none)]> show variables like 'skip%';
+---------------------------+-------+
| Variable_name | Value |
+---------------------------+-------+
| skip_external_locking | ON |
| skip_name_resolve | OFF |
| skip_networking | OFF |
| skip_parallel_replication | OFF |
| skip_replication | OFF |
| skip_show_database | OFF |

停掉skip_name_resolve后，用127.0.0.1登入转变成了localhost，用lmsapps@'127.0.0.1'的密码无法登入:
-bash-4.1$ mysql -ulmsapps -p -h 127.0.0.1 -P 3306
Enter password:
ERROR 1045 (28000): Access denied for user 'lmsapps'@'localhost' (using password: YES)

-bash-4.1$ mysql -ulmsapps -p -h 127.0.0.1
Enter password:
ERROR 1045 (28000): Access denied for user 'lmsapps'@'localhost' (using password: YES)

而用lmsapps@'localhost'登入才成功，并且使用TCP/IPt协议：
-bash-4.1$ mysql -ulmsapps -p -h localhost
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
MariaDB [(none)]>