Microsoft SQL Server Error: 53 or Microsoft SQL Server Error: 11001 or or SQL Server error 53 and 40. SQL server error 53 and 17

Details of Error:

Can not connect to SQL Server error which can be Error Number: 11001 or Error Number:53, Severity: 20, State: 0 or SQL Server error 53 and 40. SQL server error 53 and 17

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.

Connection failed
SQL State '01000'
SQL Server error 53
[microsoft][ODBC SQL Server Driver][DBNETLIB]Connection Open
Connection failed
SQL State '08001
SQL Error 17
[microsoft][ODBC SQL Server Driver][DBNETLIB]SQL Server does not exist or access denied.

(provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 53)

(provider: TCP Provider, error: 0 - No such host is known.) (Microsoft SQL Server, Error: 11001)

Cause of Error:

This error occurs when the SQL Server can’t be found on Network which means either IP address is not reachable or that the TCP port number is either not open or is not the correct port number or is blocked by a firewall etc

Resolution:

Below steps will help troubleshoot these issues

1.Check if you can Ping the Server
2.Check if Firewall is open for Connectivity
3.Check if SQL Server Service and if named instance then Browser Service is Running
4.Check if TCP/IP is Enabled in SQL Server Configuration Manager
5.Check if SQL Server has “Allow Remote Connections” set in properties on Instance level

Additional information below:

For Default instance the TCP/IP port used is 1433 but this can be changed manaully. So please check TCP IP port is still level at default 1433

Right-click on TCP/IP and select Properties.
Scroll down to IPAll.
Make sure that TCP Dynamic Ports is blank.
Make sure that TCP Port is set to 1433.

For a Named instance of SQL Server installation, Browser Service should be enabled and running which determines the SQL Server port number. The SQL browser service runs on port UDP 1434 and this must be allowed through your firewall