"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. "
Programmers often get this error message when connecting to a SQL Server named
instance. Every time a client connects to the SQL Server
named instance, an SSRP UDP packet is sent to the server machine UDP port 1434.
This is done to know the configuration information of the SQL instance, e.g.,
protocols enabled, TCP port, pipe name
etc.
Without these information, the
client does not know how to connect to the server and it fails with the above
error message.
Make a checklist of the following
1. Check your server name is correct
(typo).
- Check to see the instance name is correct and and running
- Check the server DNS (ping the server).
2. Check to ensure your database engine is configured to accept
remote connections.
- Go to Start -> All Programs -> SQL Server 2005 -> Configuration Tools -> SQL Server Surface Area Configuration
- Click on Surface Area Configuration for Services and Connections
- Select the named instance -> Database Engine -> Remote Connections
- Click Enable local and remote connections
- Restart the server
3.Check the Connection string. If you are using a named SQL
Server instance, make sure you are using that instance name in your connection
strings (machineName\Named Instance)
4.If firewall is enabled on the server make an
exception for the SQL Server instance
and port
- Go to Start -> Run -> Firewall.cpl
- Click on exceptions tab
- Add the sqlservr.exe and the default port (1433)
5.
Check the SQL Browser service is running on the server, if firewall is on make
an exception for the SQL Browser.exe
and/or UDP port 1434 .
For more information on A detailed post of
How to Troubleshoot Connecting to the SQL Server Database Engine
