Php database connect error

[IFTIKHAR AHMAD]

Hello everyone:
I am getting following error on MySQL 5.4 Windows server 2012;

A PHP Error was encountered
Severity: Warning

Message: mysqli::real_connect(): (HY000/2002): Connection refused

Filename: mysqli/mysqli_driver.php

Line Number: 202

Backtrace:

File: /var/www/vhosts/sys.lhc.gov.pk/htdoc/application/controllers/Case_management.php
Line: 37
Function: __construct

File: /var/www/vhosts/sys.lhc.gov.pk/htdoc/index.php
Line: 315
Function: require_once

A Database Error Occurred
Unable to connect to your database server using the provided settings.

Filename: controllers/Case_management.php

Line Number: 37

An expert response is highly appreciated