This check use a nginx config in default vhost like :

set $pool "www-data";
if ($arg_pool) {
  set $pool $arg_pool;
}
location ~ "/fpm-(status|ping)" {
  include       /etc/nginx/fastcgi_params;
  fastcgi_pass  unix:/var/run/php-$pool.sock;
  fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
  access_log off;
  allow 127.0.0.1;
  deny all;
}