SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Link-ID == false, connect failed
mysql error: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
mysql error number: 2002
mysql version: unknown
php version: 5.4.45-0+deb7u7
Date: 28.02.2017 @ 13:14
Script: /geburtstage.php
Referer: