SQL Server does not exist or access denied

At some point or another, you may get the following error:

SQL Server does not exist or access denied

Your exact error may differ slightly, but it’s generally in the same ballpark. Whether your clients are connecting via ODBC, OLE, natively, etc. the result is the same - no one can access Microsoft SQL Server outside of logging onto the machine and you are down.  If you RDP everything looks great and there are no errors, but you’ll find no connectivity, so it’s very eerie and somewhat strange phenomena.  Google! this error and you’ll get approximately 89,324,555,444 pages back with some sort of suggestion, because lots of folks have run into this a time or two.  And, yours truly just did the other day.

We quickly found out what the problem was, and the way that I go about looking at this is to simply use telnet; if you cannot telnet to the port the chances are very high that the port is not listening for connections.  If telnet port 23 has been disabled, well then you will have to simply try to connect from some other avenue and then decipher those errors or messages.  Telnet gives you a big blank screen, and that’s good because you have successfully connected to the port.  (see my blog for using telnet when doing Mirroring in SQL Server). Otherwise, it will return an error and you can say with a degree of confidence that something is going on with the network or server…and not SQL Server.

The Microsoft KB entitled “Potential causes of the "SQL Server does not exist or access denied" error message” is probably the best place to look when debugging this error, provided that telnet errors out.  Most cases that I have run into, either at a client or at home on my network dorking around,  relate to firewall settings on the local machine. You either need to turn the firewall off (not recommended) or “punch a hole in it”, meaning that you should open it up to the SQL Server executable so that connections can be made.  Our problem was that the anti-virus software on the server was upgraded/patched and actually turned the firewall on.  A good fail-safe here would have been to allow the executable through it in the first place.

So, if you get this, try telnet first, and if that doesn’t work use the KB to start narrowing down the list, and you will eventually find the problem.  Most likely it is not SQL Server.

Thank you

Lee Everest

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I hate errors

telnet protocol>>http://support.microsoft.com/kb/231866

KB>>http://support.microsoft.com/kb/328306