在jsch ssh客户端执行命令后，Java程序不会终止

Question

我正在使用java ssh客户端（http://www.jcraft.com/jsch/）连接到远程计算机并执行命令。代码工作正常，直到我连接到远程机器并执行命令。但问题是，即使命令执行成功，通道和会话也不会断开连接。

我也调用了session.disconnect和channel.disconnect，但问题仍然存在。

这是我的代码：

JSch jsch = new JSch();
String privateKey = "C:\\test\\key";
jsch.addIdentity(privateKey);
String host = null;
host = "192.168.102.211";
Session session = jsch.getSession("chef-admin", host, 22);
Channel channel = session.openChannel("shell");
try
{

    String cmd = "sudo su";
    String command = "chef-client";


    UserInfo ui = new MyUserInfo() {
        public boolean promptYesNo(String message) {
            return true;
        }
    };
    session.setUserInfo(ui);
    session.connect(30000);

    OutputStream ops = channel.getOutputStream();
    PrintStream ps = new PrintStream(ops, true);

    channel.connect();
    ps.println(cmd);
    ps.println(command);
    ps.close();

    InputStream in = channel.getInputStream();
    byte[] bt = new byte[1024];
        while (in.available() > 0) {
            int i = in.read(bt, 0, 1024);
            if (i < 0)
                break;
            String str = new String(bt, 0, i);
            System.out.println("valueeeeeeeeeeeeeeee is " + i);
            System.out.print(str);

    }

        System.out.println("before channel");

    }
catch (Exception e)
{
    e.printStackTrace();
}
finally
{
     if (channel != null) {
         System.out.println("finally");
            channel.disconnect();
            session.disconnect();
            System.out.println(channel.isConnected());
        }
}