JSP向SQL数据库中写下数据时提示：Network error IOException: Connection refused: connect

package db;import java.sql.Connection;import java.sql.DriverManager;public class DBcon {        private String url; // 存储SQLSever连接路径        private String serverName; // 存储机器的名称        private String portNumber; // 存储端口名称        private String databaseName; // 存储数据库名称        private String userName; // 存储用户名称        private String password; // 存储密码    /* 设置连接数据库相关参数 */        public DBcon(){                url = "jdbc:jtds:sqlserver://";                serverName = "localhost";                portNumber = "1433";                databaseName = "JSP_Test";                userName = "sa";                password = "";            }        /* 获取连接数据库路径并返回 */        private String getConnectionUrl() {               return url + serverName + ":" + portNumber + ";databaseName=" + databaseName + ";";            }        /* 获取Conncetion对象并返回 */        public Connection getConnection() {                Connection con=null;                try {                Class.forName("net.sourceforge.jtds.jdbc.Driver");     // 加载Jdbc驱动程序                                con = DriverManager.getConnection(getConnectionUrl(),userName,password);                        } catch (Exception e) {                        e.printStackTrace();                       System.out.println("getConnection()内部跟踪错误:"+ e.getMessage());        }                return con;            }}

package impl;import pojo.Student;import db.DBcon;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.SQLException;public class StudentImpl {            public void saveStudent(Student student) {        DBcon conn = new DBcon();        Connection con = null;        PreparedStatement pre = null;                con = conn.getConnection();        try {            pre = con.prepareStatement("insert into t31_Student(sname,slikes) values('?','?')");            pre.setString(1, student.getSname());            pre.setString(2, student.getSadress());            pre.executeUpdate();            con.close();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        System.out.println("StudentImpl");        System.out.println(student.getSname());        System.out.println(student.getSadress());    }    }