Why do I get a java.sql.SQLException: "Unable to get information from SQL Server" when trying to connect to an SQL Server instance?
Reason: The exception you are getting is usually caused by a timeout. When connecting to named instances jTDS needs to connect via UDP to port 1434 to get information about available SQL Server instances. While doing this it times out, throwing the exception you see (which means that jTDS was not able to get information about the running instances).
Connection timeouts occur when there is no server listening on the port. Also, check if SQL Server is configured to use TCP/IP and that you actually use named instances.
Note: On SQL Server 2005 the SQL Browser service must be running on the server host as the instance name lookup port UDP 1434 is hosted by this service on SQL Server 2005 rather than the SQL Server itself. The default install does not configure the SQL Browser service to start automatically so you must do it manually.