MSSQL FireWall rules (Allow remote connection)

If you are using a named instance, create an extra rule in your firewall with the port 1434.
Note: For a named SQL Server instance (e.g. [yourServerInstance]\SQL2012SP2), the firewall needs an extra rule on the TCP protocol with the specific port 1434. Without this rule the system will return the exception error: 26 - Error Locating Server/Instance Specified.

Display the firewall advanced settings by navigating to Control Panel > System and Security > Windows Firewall > Advanced settings.

Select Inbound Rules in the left-hand pane, then click New Rule in the right-hand pane.
In the New Inbound Rule Wizard, Rule Type step, select Port.
Protocols and Ports step, select TCP/ IP and set Specific local ports to 1434.

Action step, select Allow the connection.

Profile step, tick the Domain checkbox.

Name step, enter a name for this rule, e.g. Named instance port 1434.
Select Finish.

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