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Article Summary: This article addresses an error that may occur when attempting to connect to a SQL server.

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Issue:

A connection attempt to a SQL Server results in an error: "Could not open a connection to SQL server [53]." due to incorrect credentials or protocol configuration

Solution:

Follow the steps in the solution to resolve the issue.

1. Ensure the correct Windows credentials are supplied when connecting to the SQL Server. The current user's Windows credentials are used when Windows Authentication mode is selected on the SQL Server. The current user's Windows credentials may not be configured to access the SQL Server even though they may have elevated local or domain credentials such as belonging to the group Domain Admins or when using the Administrator account.

2. The Windows Firewall must be configured to allow access to the SQL Server. Refer to the following solution.

3. Enable the protocols on the SQL Server instance by following these steps.

a. Press Windows Logo key, type SQL Configuration Manager, right-click on it, choose Run as administrator and press Enter to open SQL Server Configuration Manager.

b. Click to arrow next to SQL Server Network Configuration to expand it.

c. Click Prococols for SQLInstance where SQLInstance is the name of the SQL Server Instance that requires configuration.




d. Ensure Shared Memory and TCP/IP are Enabled. Enable them if necessary by double-clicking on the Protocol Name and set Enabled to Yes. Click OK to save the changes.




e. Click SQL Server Services, right-click SQL Server (SQLInstance) where SQLInstance is the name of the SQL server instance and click Restart to restart the SQL Server service.

Additional Information:

This information applies to SQL Server 2012.

The error: "Could not open a connection to SQL server [53]." can be due to the use of incorrect credentials supplied during the connection process or the SQL server protocol configuration is incorrect. There may be multiple SQL Server instances on the server and each instance requires the correct protocol configuration.

Additional information about SQL Server Configuration Manager can be found on TechNet.

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