Localhost vs. 127.0.0.1 in MySQL Connections: Performance and Connection Type?

localhost and 127.0.0.1 in mysql_connect()

Question:

Does the choice between 'localhost' and '127.0.0.1' in the mysql_connect() function impact the connection speed with MySQL? Additionally, what type of connection is established between the PHP script and MySQL when using mysql_connect()? Is it based on TCP/IP?

Answer:

The performance and connection type between localhost and 127.0.0.1 differ depending on the operating system used.

Performance Differences:

• Windows: Windows typically uses TCP/IP for both localhost and 127.0.0.1, so there is no significant performance difference between the two.
• Linux: Linux attempts to use a Unix Domain Socket (UDS) when localhost is specified and TCP/IP when 127.0.0.1 is used. UDS is a faster connection method that involves less overhead compared to TCP/IP, potentially resulting in slightly faster connections when using localhost.

Connection Type:

• Windows: Both localhost and 127.0.0.1 use TCP/IP connections.
• Linux: By default, localhost uses UDS, while 127.0.0.1 uses TCP/IP. However, this can be configured in the MySQL configuration file (my.cnf) to use UDS for 127.0.0.1 connections as well.

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