SQL Server: A network-related or instance-specific error occurred while establishing a connection

This article is half-done without your Comment! *** Please share your thoughts via Comment ***

SQL Server Error: Cannot connect to .\SQL Server
“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) (Microsoft SQL Server, Error: -1)”

The above error is a very common error in SQL Server. You can find thousand of articles on this error, but still, I am sharing aggregated solution for this error.

The solutions are:

• SQL Server service status should Running, go to Start -> All Programs -> Microsoft SQL Server -> Configuration Tools -> SQL Server Configuration Manager -> SQL Server Services
• Check for SQL Server Browser Service, which should be running
• Enable UDP traffic to port 1434 because SQL Server Browser Service runs on it
• Windows Firewall should allow the incoming requests of UDP Port 1434
• Enable TCP/IP in SQL Server Configuration, go to Start -> All Programs -> Microsoft SQL Server -> Configuration Tools -> SQL Server Configuration Manager -> Select TCP/IP
• All remote connections, go to Start -> All Programs -> SQL Server -> Configuration Tools -> SQL Server Surface Area Configuration

You must restart SQL Server Services after changes.