SQL-DATABASE ERROR

Database error in WoltLab Burning Board (): Link-ID == false, connect failed
mysql error: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
mysql error number: 2002
mysql version: unknown
php version: 5.6.40
Date: 01.12.2021 @ 14:11
Script: /board.php?boardid=58&sid=6c890efa3a959b9e506826337a9c53ff
Referer: