Fatal error: Connecting to MySQL server 'mysql5.1blu.de' failed.

You get more information about the problem in our knowledge base: http://www.woltlab.com/help/?code=2005

Information:

error message: Connecting to MySQL server 'mysql5.1blu.de' failed.
error code: 2005
sql type: MySQLDatabase
sql error: Unknown MySQL server host 'mysql5.1blu.de' (111)
sql error number: 2005
sql version:
file: /hp/ab/ac/ap/www/TBS_1/wcf/lib/system/database/MySQLDatabase.class.php (29)
php version: 5.3.29
wcf version: 1.0.11 pl 4 (Horizon)
date: Sun, 16 Dec 2018 20:03:33 +0000
request: /index.php?page=User&userID=397&s=b72c66df4058bfdbd30b567d5ce2922892c99b40
referer:

Stacktrace:

#0 /hp/ab/ac/ap/www/TBS_1/wcf/lib/system/database/Database.class.php(76): MySQLDatabase->connect()
#1 /hp/ab/ac/ap/www/TBS_1/wcf/lib/system/WCF.class.php(270): Database->__construct(...)
#2 /hp/ab/ac/ap/www/TBS_1/wcf/lib/system/WCF.class.php(88): WCF->initDB()
#3 /hp/ab/ac/ap/www/TBS_1/global.php(18): WCF->__construct()
#4 /hp/ab/ac/ap/www/TBS_1/index.php(7): require_once('/hp/ab/ac/ap/ww...')
#5 {main}