基于ftp协议的文件传输程序，开发之前，一定要把ftp协议弄清楚，并且对各层数据包的格式也要知道。 好不容易才搞定，希望与大家共享！-Based on the ftp file transfer protocol procedures, the development before the ftp agreement must be clear, and the format of data packets on each floor have to know. Managed to get