Make sure that the SQL Service is running. If it is try telnetting to port 1433 on the SQL Server. If is succeeds then it’s a problem with your app. If it fails, and the SQL Server is listening correctly then there’s a firewall between the machines which is blocking the connection.
Not sure if i have put my question in the right way. I’m using Oracle SQL Developer for Queying Database. I’m not able to add any new connections, also lost all my existing connections.