In order to fix the php5-fpm.sock failed error follow these instructions
1) Make sure your virtual hosts nginx (.conf) files are using fastcgi_pass unix:/tmp/php5-fpm.sock; at the php-fpm configuration.
2) Edit nginx.conf file and make sure this variable is as follow:
user nginx;
3) Edit /etc/php-fpm.d/www.conf file and set this variables as you see below:
listen = /tmp/php5-fpm.sock listen.owner = nginx listen.group = nginx
4) Reload your services:
service nginx reload service php-fpm reload
All done, your websites now shouldn’t face any more 502 permission/owner issues because the socket has the same group as Nginx:
[root@node3.server.com:~]ls -ahl /tmp/php5-fpm.sock srw-rw---- 1 nginx nginx 0 May 6 08:08 /tmp/php5-fpm.sock
At this point, if you are still facing 502 Gateway timeout issues, check out this other post: