Question : Unable to connect to SQL Server instances

One of the servers on our network has the following instances of SQL installed:

- SQL Server 2005 (default, on port 1433)
- MSDE 2000 (Instance1, configured on port 1435)
- MSDE 2000 (Instance2, configured on port 1436)

We can connect to the 2005, and "Instance1" versions of SQL fine from PCs on the same network, however cannot connect to "Instance2" - it times out with the error "SQL Server does not exist or access denied. ConnectionOpen (Connect())".

We can get around this issue by using the "cliconfg" utility on the client PCs to specify the instance name, e.g. "ServerName\Instance2", and specifying the port to use.  However we didn't have to use "cliconfg" for setting up "Instance1", and one of the applications we use appears to overwrite the port number setting in "cliconfg", so it is imperative we find a solution to this without having to resort to specifying the port number on the client PC (i.e. the client PC should be able to automatically determine the port number to use).

Both instances of MSDE have the same configuration options set, i.e. TCP/IP enabled, same permissions etc.

We have tried uninstalling "Instance1" and "Instance2", restarted the server, and installed a fresh instance "NewInstance", and now have the same issue connecting to that instance, i.e. cannot connect from client PCs without first configuring the "NewInstance" on the client PCs using "cliconfg"!

Does anyone know why some instances work straight away, but others don't, without first configuring the instance on the client PC using "cliconfg", and specifying the port number?

Any help with this would be much appreciated.

Answer : Unable to connect to SQL Server instances

Did  you check for the sql browser service (on server)? If it runs, it should allow for 1434/udp broadcasts and return the installed instances with port.