the main task of the Internet and its TCP/IP protocol suite is to provide
services for users. Although there are some specific client/server programs
that we discuss in future chapters, it would be impossible to write a
specific client-server program for each demand. The better solution is a
general-purpose client-server program that lets a user access any application
program on a remote computer; in other words, allow the user to log
on to a remote computer. After logging on, a user can use the services
available on the remote computer and transfer the results back to the local
computer. In this chapter, we discuss two of these application programs:
TELNET and SSH.