The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Key Applications and Application Protocols            9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)                 9  TCP/IP General File Transfer Protocols (FTP and TFTP)                      9  File Transfer Protocol (FTP)                           9  FTP Commands and Replies

FTP Internal Protocol Commands and Command Groups 1 2 3 4 5 FTP User Interface and User Commands

Combining Digit Values to Make Specific Reply Codes

These “x”, “y” and “z” digit meanings are combined to make specific reply codes. For example, consider reply code “530”, diagrammed in Figure 292. The first digit tells you that this is a permanent negative reply; the second indicates that it is related to login or accounting. (It is in fact an error message received when a login fails.)

Using “encoded” reply codes allows the code itself to immediately communicate information, and provides a way of keeping different types of responses organized. The idea described above was adapted for use by several other application protocols, including SMTP for e-mail, NNTP for network news and HTTP for the World Wide Web.

FTP Internal Protocol Commands and Command Groups 1 2 3 4 5 FTP User Interface and User Commands