Network-related or instance-specific errors occur when you establish a connection with SQL Server. The server is not found or cannot be accessed.

Problem: Network-related or instance-specific errors occur when you establish a connection with SQL Server. The server is not found or cannot be accessed. Verify that the Instance name is correct and SQL server is configured to allow remote connection. (Provider: Named Pipes provider, error: 40-unable to open the connection to SQL Server)

 

Solution:

1,Program--- Microsoft SQL Server 2005-Configuration tool --- SQL Server Configuration Manager --- network connection protocol --- Select the instance protocol --- enable (shard memory, named pipes, TCP/IP)
Let's take a look at whether Windows Firewall is off or set 1433 (default SQL port) as an example.