The networking operation of TCP/IP between the client and server running SQL Server is not operable. You can check TCP/IP connectivity to SQL Server by using telnet. For example, at the command prompt, type
telnet 192.168.0.0 1433 where 192.168.0.0 is the address of the computer that is running SQL Server and 1433 is the port it is listening on. If you receive a message that states "Telnet cannot connect," TCP/IP is not listening on that port for SQL Server connections. Use the SQL Server Network Utility for SQL Server 2000 (8.x), or the SQL Server Configuration Manager for SQL Server 2005 (9.x) and later to make sure that SQL Server is configured to use TCP/IP on port 1433.