Let us now turn our attention to the nature and syntax of the FTP protocol.
It may be obvious now but it is worth noting that the FTP is implemented using the TCP Protocol.
Like the email protocols SMTP and POP, you enter into a dialog with a (FTP) server: you supply possibly a username and password (or anonymous aliases) an then proceed to download and upload files.
If you use more the command line based (UNIX/DOS) ftp clients or the more fancy FTP clients such as Fetch or InterArchie then the Protocol converstaion is taken of for you. Although you may notice aspects of the FTP transaction in the main and message windows of these applications (Check out the manuals for more details).
Note that if you use the command line based (UNIX/DOS) ftp clients you can turn on debug to see the Protocol command conversation and use quote to converse in the protocol yourself (see Section 4.6.4).
Note that every request is replied to with a code -- a number that indicates whether the requested command is executes correctly or in error.
We should have fairly good idea of the operations required by an FTP client in order download/upload files so lets jump straight in and look at the actual protocol commands.