Microsoft: Microsoft SQL Network Error 26

Error Message:
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Solution:
1.  Determine the port that your SQL server is listening by opening CMD in your SQL server ( Run as administrator ) and running the following command to obtain the connecting port:

netstat /abo >>c:\output.txt

* Note: The default port should be 1433

2.  In your SQL server, go to Control Panel >> Windows Firewall and click on Advanced Settings on the left pane. You should see the Windows Firewall with Advanced Security.

3.  Select the Inbound Rules on the left pane and click on New Rule... on the right pane.

4.  This opens the New Inbound Rule Wizard which you can use to allow inbound traffic on Port 1433 for TCP/IP. Just follow the steps outlined below for the configuration.

5.  Create exception of sqlbrowser.exe. Sqlbrowser service needs to be enabled for named instance. Windows Firewall may prevent sqlbrowser.exe to execute. So, it is imperative to add exception for the same in Windows Firewall. Firstly, search for sqlbrowser.exe on your local drive where SQL Server is installed. Copy the path of the sqlbrowser.exe ( * Note: C:\Program Files\Microsoft SQL Server\90\Shared\sqlbrowser.exe ) and create the exception of the file in Firewall, as delineated in Step 4 except this time please select Program rather than Port.

That’s it, success! From here you should be able to access your SQL Server remotely.


References:
1.   How to enable remote connections in SQL Server 2008?
http://blogs.msdn.com/b/walzenbach/archive/2010/04/14/how-to-enable-remote-connections-in-sql-server-2008.aspx

2.  How to determine and change the port of an SSAS Instance
http://support.microsoft.com/kb/2466860

3.  SQL SERVER – FIX : ERROR : (provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: )
http://blog.sqlauthority.com/2009/05/21/sql-server-fix-error-provider-named-pipes-provider-error-40-could-not-open-a-connection-to-sql-server-microsoft-sql-server-error/