jdbc连接SQL server连不上

com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host 127.0.0.1, port 1433 has failed. Error: Connection refused: connect. Please verify the connection properties and check that a SQL Server instance is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port. at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:130) at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectHelper(SQLServerConnection.java:1195) at com.microsoft.sqlserver.jdbc.SQLServerConnection.loginWithoutFailover(SQLServerConnection.java:1054) at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(SQLServerConnection.java:758) at com.microsoft.sqlserver.jdbc.SQLServerDriver.connect(SQLServerDriver.java:842) at java.sql.DriverManager.getConnection(DriverManager.java:664) at java.sql.DriverManager.getConnection(DriverManager.java:247) at javaapplication3.JavaApplication3.JDBCon(JavaApplication3.java:27) at javaapplication3.JavaApplication3.main(JavaApplication3.java:18)