The Microsoft JDBC Driver for SQL Server requires that TCP/IP be installed and running to communicate with your SQL Server database. You can use the SQL Server Configuration Manager to verify which network library protocols are installed.
A database connection attempt might fail for many reasons. These can include the following:
TCP/IP is not enabled for SQL Server, or the server or port number specified is incorrect. Verify that SQL Server is listening with TCP/IP on the specified server and port. This might be reported with an exception similar to: "The login has failed. The TCP/IP connection to the host has failed." This indicates one of the following:
SQL Server is installed but TCP/IP has not been installed as a network protocol for SQL Server by using the SQL Server Network Utility for SQL Server 2000, or the SQL Server Configuration Manager for SQL Server 2005 and later.
TCP/IP is installed as a SQL Server protocol, but it is not listening on the port specified in the JDBC connection URL. The default port is 1433, but SQL Server can be configured at product installation to listen on any port. Make sure that SQL Server is listening on port 1433. Or, if the port has been changed, make sure that the port specified in the JDBC connection URL matches the changed port. For more information about JDBC connection URLs, see Building the Connection URL.
The address of the computer that is specified in the JDBC connection URL does not refer to a server where SQL Server is installed and started.
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, or the SQL Server Configuration Manager for SQL Server 2005 and later to make sure that SQL Server is configured to use TCP/IP on port 1433.
The port that is used by the server has not been opened in the firewall. This includes the port that is used by the server or optionally, the port associated with a named instance of the server.
The specified database name is incorrect. Make sure that you are logging on to an existing SQL Server database.
The user name or password is incorrect. Make sure that you have the correct values.
When you use SQL Server Authentication, the JDBC driver requires that SQL Server is installed with SQL Server Authentication, which is not the default. Make sure that this option is included when you install or configure your instance of SQL Server.