JSCH上传文件到linux服务器打开远程目录报空指针异常

最近的项目要用jsch把本地文件上传到服务器，但是出现问题：

public static void main(String[] args) {

        try {
            upload("/home/informix", "C:\\Users\\Administrator\\Desktop\\upload.jsp", getSession());
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSchException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SftpException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    //获得指定用户session
    public static Session getSession() throws JSchException {
        JSch jsch = new JSch();// 创建JSch对象
        Session session = jsch.getSession("informix", "192.168.226.166", 22);
        session.setPassword("ffcsffcs");
        Properties config = new Properties();
        // 设置 SSH 连接时不进行公钥确认
        config.put("StrictHostKeyChecking", "no");
        session.setConfig(config);
        session.connect();
        return session;
    }
 //上传单个文件
    public static void upload(String remotePath, String uploadFile, Session session)
            throws JSchException, FileNotFoundException, SftpException {
        ChannelSftp channelSftp = (ChannelSftp) session.openChannel("sftp");
        channelSftp.cd(remotePath);
        File file = new File(uploadFile);
        channelSftp.put(new FileInputStream(file), file.getName());
        //channelSftp.put(new FileInputStream(file), remotePath, ChannelSftp.OVERWRITE);
        System.out.println("Upload Success!");
    }

异常：
4:
at com.jcraft.jsch.ChannelSftp.cd(ChannelSftp.java:285)
at cn.ffcs.util.JSchUtils.upload(JSchUtils.java:121)
at cn.ffcs.util.JSchUtils.main(JSchUtils.java:29)
Caused by: java.lang.NullPointerException
at com.jcraft.jsch.Packet.reset(Packet.java:43)
at com.jcraft.jsch.ChannelSftp.sendPacketPath(ChannelSftp.java:2025)
at com.jcraft.jsch.ChannelSftp.sendREALPATH(ChannelSftp.java:1954)
at com.jcraft.jsch.ChannelSftp._realpath(ChannelSftp.java:1807)
at com.jcraft.jsch.ChannelSftp.cd(ChannelSftp.java:268)
... 2 more

求大神指点

https://blog.csdn.net/lyl0724/article/details/79932270