Pripojenie databazy

Zdravim, pripajam databazu k webu cez subor connect.php, zadal som:

$con = mysqli_connect($host,$user,$password,$db);

Premenne som definoval s prihlasovacimi udajmi a vypise mi tuto chybu: Chyba spojenia s db: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. 

Nejake napady ako to opravit? Budem velmi vdacny.