FTP客户端从FTP服务器下载文件文件内容为空？

下载部分代码： public synchronized boolean download(String remoteFile,String localFile) throws IOException {

        dataSocket = createDataSocket();
        sendCommand("RETR " + remoteFile);
        response = readLine();
        if (!response.startsWith("1")) {
            System.out.println(response);
        }
        System.out.println(localFile);
        FileOutputStream fileOut = new FileOutputStream(localFile);
        BufferedInputStream dataIn = new BufferedInputStream(dataSocket.getInputStream());
        new File(localFile).createNewFile();
        byte[] buffer = new byte[4096];
        int bytesRead = 0;
        do {
            bytesRead = dataIn.read(buffer);
            if (bytesRead != -1) {
                fileOut.write(buffer, 0, bytesRead);        //将byte[]数组下标0开始的bytesRead
                                                            //长度的数据写入当前输出流
            }
        } while (bytesRead != -1);
        fileOut.flush();
        fileOut.close();
        dataSocket.close();
        response = readLine();

        if (response.startsWith("226")) {
             JOptionPane.showConfirmDialog(null,
                    "下载成功",
                    " 下载信息", JOptionPane.CLOSED_OPTION,
                    JOptionPane.INFORMATION_MESSAGE);         
        }
        return (response.startsWith("226"));
    }

``` public boolean uploadFile(String path,FileInputStream in) throws Exception { DataConnect dc=getDataStream(2);

    try {
        String line=sendCmd("STOR "+path+"\r\n");
        if(line.startsWith("125")) {
            OutputStream out=dc.getDataOut();
            int len=0;
            byte[]bb=new byte[1024*4];
            while((len=in.read(bb))>0) {
                out.write(bb,0,len);
            }
            return true;
        }else {
            return false;
        }
    }catch(Exception e) {
        e.printStackTrace();
    }finally {
        dc.destoryOutput();
    }
    return false;
}