SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6 pl2): Link-ID == false, connect failed
mysql error: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111)
mysql error number: 2002
mysql version: unknown
php version: 5.5.9-1ubuntu4.14
Date: 01.10.2022 @ 16:29
Script: /board,boardid-57.html
Referer: