Highlights of RFC 959WS_FTP ProAppendix A: Highlights of RFC 959This appendix includes some highlights of RFC 959, “File Transfer Protocol.” This information is provided here for those advanced users who want to know more about how FTP works. It will also assist those wishing to interpret the messages at the bottom of the WS_FTP Pro Classic main window or in the log window. Topics included here are:• Basics• FTP Commands• FTP Replies (three-digit “error codes”)For more detailed information, see the RFC itself.BasicsFTP (File Transfer Protocol) is a specification for how files can be transferred over the Internet. FTP is a client-server protocol in which FTP client software on one system communicates with FTP server software on another. The communication between the FTP client and server is an exchange of commands and replies which are transmitted over a “control connection” between the two systems; this control connection follows the Telnet model.Files are transferred between the client and server over a second connection, a full duplex connection known as the “data connection.” This connection is between the client’s “data transfer process” and the server’s data transfer process (or between two servers’ data transfer processes).Data connectionFTP Client FTP ServerProtocol interpreterProtocol interpreterData transfer processData transfer processFile systemFile system Control connection: FTP commands and replies
