FTP is the quintessential line-oriented server application. Every command issued by the client takes the form of a single, easily parsed line, and each response from the server to the client follows a predictable format. Many of the server applications that we discuss in later chapters, including POP, SMTP, and HTTP, are similarly simple. This is because the applications were designed to interact primarily with software, not with people.
Telnet is almost exactly the opposite. It was designed to interact directly with people, not software. The output from a Telnet session is completely unpredictable, depending on the remote host's configuration, the shell the user has installed, and the setup of the user's environment.
Telnet does ...