PHP listen to unix socket

Question

So in short I'm trying to get a PHP script to listen for requests over unix sockets and send it a request from another PHP script. I have configured PHP-FPM as such:

[a]

; Unix user/group of processes
user = www
group = www

listen = /var/run/php-fpm-a.sock
;listen.backlog = -1

listen.owner = www
listen.group = www
listen.mode = 0660

; Choose how the process manager will control the number of child processes.
pm = dynamic
pm.max_children = 75
pm.start_servers = 3
pm.min_spare_servers = 1
pm.max_spare_servers = 5
pm.max_requests = 500

; host-specific php ini settings here
php_admin_value[open_basedir] = /usr/local/www/a
php_flag[display_errors] = on
/usr/local/www/a contains the following index.php:

<?php
echo 'test\ntest\ntest\n';

There is another PHP-FPM config file that effectively listens at /var/run/php-fpm-b.sock and Nginx points to it (this bit works fine), this contains the following code in /usr/local/www/b/index.php:

echo 'TEST B';
$fp = fsockopen('unix:///var/run/php-fpm-a.sock', -1, $errno, $errstr, 30);
if (!$fp) {
  echo "$errstr ($errno)<br />\n";
} else {
  $out = "GET /index.php HTTP/1.1\r\n";
  $out .= "Host: localhost\r\n";
  $out .= "Connection: Close\r\n\r\n";
  fwrite($fp, $out);
  while (!feof($fp)) {
    echo fgets($fp, 128);
  }

  fclose($fp);
}

Clearly I have something wrong in /usr/local/www/b/index.php as all I get is "TEST B" as the output. I don't think it's a socket permission issue as it would state so with an error, my guess is $out is wrong for this to work but have no idea what PHP excepts to receive. Any help would be appreciated.

Note: using PHP7 on FreeBSD11

Nginx uses FastCGI protocol to communicate with PHP-FPM process. Why you're trying to do it via HTTP? — Ivan Velichko
– Ivan Velichko, Commented Nov 22, 2016 at 13:47
Ignore Nginx, that part works fine, I basically want one PHP script to connect to another with unix sockets as if one is a client and the other a server without going via Nginx if possible. — FireLeopard
– FireLeopard, Commented Nov 22, 2016 at 13:52
I mean, that you have to use FastCGI proto as well while communicating with the second script. — Ivan Velichko
– Ivan Velichko, Commented Nov 22, 2016 at 14:27
@IvanVelichko told you everything - two different FPM's can speak only via FCGI, but you're using HTTP as the protocol - that can't work. Also, this looks like XY problem. Why do you need two FPM's communicating with each other without anything in the middle? Are you trying to ping FPM's to see if they're alive or? — Mjh
– Mjh, Commented Nov 22, 2016 at 16:41
@Mjh There will actually be things in the middle, it was just to get the bare minimum working. — FireLeopard
– FireLeopard, Commented Nov 22, 2016 at 16:52

Ivan Velichko · Accepted Answer · 2016-11-22 14:47:43Z

2

PHP-FPM is a FastCGI Process Manager. FastCGI and HTTP are two different protocols. So, PHP-FPM can't speak HTTP directly.

browser -> (HTTP) -> nginx -> (FastCGI) -> PHP-FPM + scriptB
scriptB -> (HTTP) -> PHP-FPM + scriptA

You have two options:

Put script A behind nginx and then open TCP socket instead of unix socket to communicate from B to A.
Modify script B to speak in FastCGI language with script A instead of HTTP.

answered Nov 22, 2016 at 14:47

Ivan Velichko

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5 Comments

FireLeopard Over a year ago

Thanks, I've opted for the first option, which thinking about it is far better than trying to over-engineer it. I did know FastCGI and HTTP were different but I guess I was just hoping PHP-FPM could understand both.

Ivan Velichko Over a year ago

You're welcome. However, if this problem wasn't an educational one, I suggest you to use something like cURL or even file_get_contents() instead of manually open sockets.

Mjh Over a year ago

@FireLeopard the problem is that php-fpm is not an http server, therefore it doesn't have to understand http. Having it speak fastcgi only lets you place one or multiple php-fpm servers behind any web server, be it nginx, apache, mix of both, or something completely different. HTTP servers can adjust to the protocol http 1.1 or http 2.0 without having to upgrade php-fpm servers. There are reasons for all of this, there are ways to translate http to fcgi, but as you said - it's the best not to overengineer it.

Adrian Preuss Over a year ago

The answer is from 2022 but actually i have a question: How we can communicate with php-fpm? Where is a great specification for that?

Ivan Velichko Over a year ago

@AdrianPreuss the Wikipedia page of the FastCGI protocol has this link - might be helpful.

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