FTP的目标是提高文件的共享性，提供非直接使用远程计算机，使存储介质对用户透明和可靠高效地传送数据。虽然我们也可以手工使用它，但是它的主要作用是供程序使用的。在阅读本文之前最好能够阅读TCP协议标准规范和Telnet协议标准规范。-FTP goal is to improve the sharing of documents, and provide non-direct access to remote computers, so that storage medium transparent to the user and reliable transmission of data efficiently. Although we can also use it manually, but its main role is used for the procedure. Before reading this article at best be able to read the standard TCP protocol and the standard Telnet protocol.