The client runs the telnet progam, the server, or host runs telnetd (the telnet daemon). The connection is continuous.
The client runs the ftp program, and server runs ftpd (the ftp daemon). The connection is continuous. The Mac version of ftp that is commonly use is called Fetch, written at Darmouth College. FTP can be used to move files back and forth between Athena home directories and the hard disk of a Mac or PC that is on MITnet.
This client/server application was very popular for a few years in the early 90's, before Web browsers took over. A gopher server would present a menu of items (each item being a file or a directory).The client would traverse the menu, in the end displaying or retrieving a file via the ftp protocol. Most universities (including MIT) turned off their Gopher servers once the WorldWideWeb became the method of choice for disseminating information.
The client runs a brower, e.g. Mosaic, Netscape, Lynx. The server runs httpd (the http daemon). The connection is "stateless." I.e., a request goes across the network from the client to a Web server, and the reply comes back. The connection is then broken, with no information about the client remaining on the server. WWW browsers can also connect to ftp and telnet server machines.
The client runs a news reader (rn, xrn, or a News reader on a Mac or PC). The server responds by displaying news articles, allowing for posting, forwarding, saving, etc. Some news readers allow the user to follow threads.
The client runs a Mail reader (e.g. mh, xmh, Eudora). The server stores mail messages until they are downloaded to the user's hard disk or home directory. If also accepts new messages sent by the user and sends them off.
Instaneous messaging system
Conferencing and archiving system
On-Line Consulting system