Summary of differences between MySQL host 127.0.0.1 and localhost

Source: Internet
Author: User
Tags mysql host unix domain socket
Many of my friends may encounter a problem. I don't know what is the difference between 127.0.0.1 and localhost. However, sometimes I find that the connection fails when I use localhost, but I changed it to 127.0.0.1, so what are their differences? I will introduce them to you below.

Many of my friends may encounter a problem. I don't know what is the difference between 127.0.0.1 and localhost. However, sometimes I find that the connection fails when I use localhost, but I changed it to 127.0.0.1, so what are their differences? I will introduce them to you below.

1. mysql-h 127.0.0.1 is connected using TCP/IP. mysql server considers the connection from 127.0.0.1 or "localhost. localdomain"

2. When mysql-h localhost is used, Unix socket is used instead of TCP/IP connection. At this time, mysql server considers that the client is from "localhost"

3. "localhost" in mysql permission management has specific meanings:

Note: although there are differences between the two connection methods, when localhost is 127.0.0.1 by default, the permission records used by the two connection methods are the following 1. row record (because the record is first matched)

The Code is as follows:
* *************************** 1. row ***************************
Host: localhost
User: root
......
* *************************** 2. row ***************************
Host: 127.0.0.1
User: root

Proof:

The Code is as follows:

Shell> mysql-h 127.0.0.1
Mysql> status;
Current user: root @ localhost
SSL: Not in use
Current pager: stdout
Using outfile :''
Using delimiter :;
Server version: 5.1.33-log Source distribution
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP
Shell> mysql-h locahostmysql> status;
Current user: root @ localhost
SSL: Not in use
Current pager: stdout
Using outfile :''
Using delimiter :;
Server version: 5.1.33-log Source distribution
Protocol version: 10
Connection: Localhost via UNIX socket

Problems Found
I encountered a problem yesterday when I was helping my colleagues compile and install the Linux environment:

The WEB server is apache and the database is MySQL.

So I wrote a PHP page to test the connection to the database:

The Code is as follows:

$ Mysql = mysql_connect ('localhost', 'root ','');

Open http: // localhost/test. php to test

Tip: Can't connect to local MySQL server through socket...

Check that the environment is normal
I thought the database was not started, so I checked the process. MySQL restarted MySQL in the process.

Use mysql-u root-p to enter the MySQL operation interface

You can directly use/usr/local/php5/bin/php/web/test. php to connect to the database.

Apache is also restarted, which is also invalid.

Question: Why does the web page fail to be executed but the command is successfully executed?
This is depressing. If you use the php Command to directly execute the command, the execution will fail through the web page. Is it caused by apache? No solution was found after searching a bunch of materials on the Internet, and the problem of re-Compiling and installing apache still persists.

Changed localhost to 127.0.0.1.
After I changed localhost to 127.0.0.1, the connection was successful and I began to think about the dilemma: Why did the localhost fail 127.0.0.1 but it succeeded?

The ping localhost address is 127.0.0.1.

Open hosts to join

The Code is as follows:

127.0.0.1 qttc

When qttc is used, the host connection is normal, but localhost is not recognized.

Due to different localhost connection methods
To learn about the differences between localhost and other settings when using PHP to connect to the database, I read a lot of information and finally learned:

When the host is set to localhost, mysql uses unix domain socket connection.

Mysql uses tcp connection when the host is set to 127.0.0.1.

This is a feature of the linux Socket network, and the win platform does not have this problem.

Solution
In the [mysql] section of my. cnf, add

The Code is as follows:

Protocol = tcp

Save and restart MySQL. The problem is solved!

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