When using SQL Server, we all encounter the problem that we cannot connect to the remote database instance using SQL Server Management Studio. The error description information is summarized as follows:
An error has contracted a connection to the server.
(provider: Named Pipes provider, error: 40 — Could not open a connection to SQL server)
An error has been sent to the server. 5)
An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 — Could not open a connection to SQL Server (Microsoft SQL Server, 1326)
— Could not open a connection to SQL Server (Microsoft SQL Server, 1326)
) In fact, this is a more typical database server setup problem, in the LAN or wan may be encountered, we only need to do some configuration of the database server can solve this problem, to see the specific steps.

The reason is that I modified the computer name and logged in with the original user name, so the above error occurred.
The solution is to re-search the SQL Server server and log in.