The database operation failed: "No connection could be made because the target machine actively refused it" (4258304)

The database operation failed: "No connection could be made because the target machine actively refused it"

Error installing on a cluster on a separate domain:

No connection could be made because the target machine actively refused it

Followed KB 88204 to be able to connect via fully qualified domain name (FQDN).

Things to check:

1.  Login to your middleware.
   
   a.  If you have a SQL Server Management Studio:
   Try connecting to hostname_fqdn\instance_name with port as the Foglight service account
   
   b.  Perform a UDL test
   - Open a Windows explorer | right-click | create a file
   - Rename that file with a UDL extension (e.g. test.udl)
   - Under the Provider tab, select SQL Server provider
   - Go to Connection tab | Enter this: hostname_fqdn\instance_name,<port>
   - Supply the login information, if you were able to login as the Foglight service account, do that so you can select "Use Window NT Integrated Security"
   
   
2.  If all steps in item 1 fails, switch the hostname from hostname_fqdn to hostname (without the FQDN) and redo the tests.  

3.  If it still fails, do this from the middleware:

   a.  telnet hostname_fqdn <port>
   b.  telnet hostname <port>
   
4.  Other things to check:
   a.  Is there a firewall between these 2 hosts?
   b.  Is there an antivirus on the SQL server that may be blocking the connection
   c.  Is TCP/IP protocol enabled for the SQL Server instance
   d.  Have you confirmed that Foglight service account is granted permission in the SQL Server security?