问Java SSH连接:获取空异常

EN

try{
      JSch jsch=new JSch(); 
      String host=selectedItem.getHost();
      String user="down2home";
      int port = selectedItem.getPort();
      String password = selectedItem.getPass();
      String dlurl = dlurlField.getText().toString();

      Session session=jsch.getSession(user, host, port);
      session.setPassword(password);
      UserInfo ui = new MyUserInfo(){
      };
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      String command = "curl -L --create-dirs -o /home/paul/Desktop/geeknights/geeknights.mp3 "+dlurl+"\r\n";
      out.write(command.getBytes());
      out.flush();
      InputStream in = new ByteArrayInputStream(out.toByteArray());
      session.setUserInfo(ui);
      session.connect(30*1000);   // making a connection with timeout.
      Channel channel=session.openChannel("shell");
      channel.setInputStream(in);
      channel.setOutputStream(System.out);
      channel.connect(3*1000);
    }
    catch(Exception e){
        String errorMessage = (e.getMessage()==null)?"Message is empty":e.getMessage();
        Log.e("Exception:", errorMessage );  
    }

06-08 00:33:16.561: E/Exception:(9293): Message is empty