How to Solve error: 40 in SQL - Could not open a connection to SQL Server

The error "error: 40 - Could not open a connection to SQL Server" istelf can be caused by several reasons.  The 

additional error code often helps to narrow down the problem. 

For example, the original post lists this:

"... (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL

 Server, Error: 2)"

- error 40 is generated by the SqlClient provider, and is somehwat generic in this case. 

- error 2 is the "winerror" that comes from the OS, and is more specific: ERROR_FILE_NOT_FOUND in this case 

(see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/randz/protocol/winerror_h__part_1.asp). 

ERROR_FILE_NOT_FOUND most frequently indicates that the client attempted a connection to the *local* SQL 

Server but the server is either not available, not running, or not accepting connections.  One possibility is that 

the server was specified as ".", "(local)" (or ".\SQLEXPRESS", "(local)\SQLEXPRESS").  If a connection to a remote 

server is desired the actual name of the server must be used instead of ".". 

With regard to connections to a default instance server that listens on a non-stadard TCP port: Client Network 

Utility cannot be used to configure the default target TCP port used by .Net Fraemwork 2.0 (or VS2005).  You 

either need to specify the port in the connection string, e.g. if the port is 1500 you can specify 

"targetServer,1500", or you can create an alias specifying the TCP port (here, Client Network Utility can be used).