SQL Server: General Connectivity Troubleshooting Checklist
- Check the server & instance name.
- Check the SQL Server instance is using the required protocol. For example, TCP/IP is not enabled by default.
- Check the SQL Server instance is configured to listen over the port you think it is.
- Check the SQL Server instance is actually listening over the port. For example, use the following command:
netstat -an | find "1433"
This shows all processes active using port 1433.
(If the SQL Server instance is configured to use a listening port that falls within Windows' ephemeral port range, that port will need to be reserved. See Various Windows Services Fail After Reboot.)
- Check the firewall is allowing access to the desired port, and for all interfaces required (domain/private etc), and the desired scope (local subnet etc).
- Check the SQL Server instance is allowing the desired authentication types, eg Windows authentication only or Mixed Mode (Windows authentication & SQL Server logins).
- Check the username and password if using SQL Server logins.