localhost vs. 127.0.0.1 in mysql_connect()

Question

Does using localhost in mysql_connect() make the connection faster than using 127.0.0.1?
What is the connection type between the PHP script and mySQL (when using the mysql_connect() function) ? Is it TCP/IP?

score 83 · Accepted Answer · edited Oct 08 '13 at 01:21

83

Differs between Windows and Linux. If you use a unix domain socket it'll be slightly faster than using TCP/IP (because of the less overhead you have).
Windows is using TCP/IP as a default, whereas Linux tries to use a Unix Domain Socket if you choose localhost and TCP/IP if you take 127.0.0.1.

edited Oct 08 '13 at 01:21

doitlikejustin

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answered Sep 15 '10 at 08:36

halfdan

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Thank you! Why doesn't Apache interact through TCP/IP or socket based connection with PHP? – Joel Sep 15 '10 at 08:44
Apache uses either mod_php or connects to PHP using TCP/IP or Unix Domain Socket (when configured to run via fastcgi). – halfdan Sep 15 '10 at 08:49
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+ the nasty thing in linux is when you specify 'localhost' as host, and a specific port, it just ignores the whole port bit and uses the default socket, not something one wants when running multiple servers on a single machine (hence the different port..). – Wrikken Sep 15 '10 at 10:21
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@Wrikken, that's true, but easily avoidable by using 127.0.0.1:port – halfdan Sep 15 '10 at 10:28
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@halfdan: indeed, but something one needs to know _before_ proceeding to demolish some tables :P Ah, live and learn, it was a while back and I'll never forget it. – Wrikken Sep 15 '10 at 10:48
also, 127.1 is synonymous with 127.0.0.1 . try it. – djangofan Sep 15 '10 at 21:32
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@djangofan: No? 127.1 is not a valid IP address. It _could_ work as a fallback by the database driver. – halfdan Sep 15 '10 at 21:41
In Windows 10 and 11 is significantly faster to use 127.0.0.1! – Johntor Feb 20 '23 at 11:48

Piotr Pankowski · Answer 2 · 2010-09-15T08:45:18.120

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"localhost" means local socket connection while 127.0.0.1 is TCP/IP. And yes, sockets are faster than TCP/IP.

Cite from http://pl.php.net/mysql_connect

Whenever you specify "localhost" or "localhost:port" as server, the MySQL client library will override this and try to connect to a local socket (named pipe on Windows). If you want to use TCP/IP, use "127.0.0.1" instead of "localhost". If the MySQL client library tries to connect to the wrong local socket, you should set the correct path as in your PHP configuration and leave the server field blank.

edited Sep 15 '10 at 08:45

answered Sep 15 '10 at 08:37

Piotr Pankowski

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TCP/IP is also socket based. I know what you mean, but you'll confuse people with it. – halfdan Sep 15 '10 at 08:38
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It could be `Unix-socket connection` – helios Sep 15 '10 at 08:39
You are right. I changed this to "local socket" to clarify. Thanks for noticing. – Piotr Pankowski Sep 15 '10 at 08:43

score 16 · Answer 3 · edited Sep 26 '12 at 19:05

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Nope, the 127.0.0.1 is recommended to use , because Windows 7 has a problem with choosing between IPv6 & IPv4. I tried this and if I used localhost, the page has reloading about 1sec (1,04sec) and when i used 127.0.0.1, the page has reloading 50ms. Both were used under Windows 7.
In Windows XP it doesn´t make difference.

edited Sep 26 '12 at 19:05

SeanC

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answered Sep 26 '12 at 11:27

Vasekdvor

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Had the same experience. Going from localhost to 127.0.0.1 dropped my latency from 1 second to 5 ms. Thanks! – Nathan Bedford Sep 25 '14 at 16:08
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That's because windows had dropped localhost from the hosts file in later versions so it takes a long time to resolve. – Nimeshka Srimal Jul 08 '18 at 07:54

score 2 · Answer 4 · edited Dec 19 '12 at 18:43

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For Unix, add to the client block after [client] in /etc/mysql/my.cnf this line :

protocol=tcp

edited Dec 19 '12 at 18:43

John Conde

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answered Dec 19 '12 at 18:25

Igael

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score 0 · Answer 5 · answered Oct 24 '13 at 00:07

For macs, here's the solution:

Connect to MySQL using localhost instead of 127.0.0.1 on a MAC. For a long while now I’ve been connecting to MySQL on my development platform with 127.0.0.1 because for some reason localhost didn’t work. Turns out it’s because 127.0.0.1 uses TCP/IP and localhost uses sockets. The php.ini file points to the wrong place for the mysql.sock so all you have to do is change it, restart apache and voila!

Open php.ini: /private/etc/php.ini
Find the following line: mysql.default_socket = /var/mysql/mysql.sock
Replace with: mysql.default_socket = /tmp/mysql.sock
Restart apache: apachectl restart

Note: If you don’t have a php.ini file, you need to copy the provided default called php.ini.default

sudo cp /private/etc/php.ini.default /private/etc/php.ini

via http://madproject.com/general/connect-to-mysql-using-localhost-instead-of-127-0-0-1-on-a-mac/

score 0 · Answer 6 · answered Sep 15 '10 at 08:41

Php site says:

Note:

Whenever you specify "localhost" or "localhost:port" as server, the MySQL client library will override this and try to connect to a local socket (named pipe on Windows). If you want to use TCP/IP, use "127.0.0.1" instead of "localhost". If the MySQL client library tries to connect to the wrong local socket, you should set the correct path as in your PHP configuration and leave the server field blank.

I guess the speed difference would be too low that it's something you should'nt be worried about.

score 0 · Answer 7 · answered Jul 23 '21 at 23:13

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It is not true that localhost is faster, but is rather a bit slower.

That being said, if you are connecting to someone else; catch my drift?

Who is to say which side of the connection fails harder? No one. That:

127.0.0.1 is a faster ping than localhost. Try on any Terminal.

answered Jul 23 '21 at 23:13

0b00000001

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Right @Php site! The difference is insubstantial to most users... LET US NOT LEAVE IT THERE! – 0b00000001 Jul 23 '21 at 23:14

localhost vs. 127.0.0.1 in mysql_connect()

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