Dave D. (11/4/2010)
The question that comes to mind with that is why I could connect to the database if didn't put the named instance in the connection string? Does it communicate differently?
When you're connecting to the default instance, it uses TCP port 1433.
When you're connecting to a named instance, the port is unknown and has to be returned by SQLBrowser.
And what tool can I use best to see if the TCP and UDP ports of a machine are open?
You can use netstat to check listening ports on the server, but this is not sufficient.
To check if the server is available from the remote host, you can use portquery, that is shipped with a specific check for sql browser.
-- Gianluca Sartori