Client/Server          Protocol

e-mail sender/server        SMTP  - Simple Mail Transport Protocol 

e-mail reader/server        POP   - Post Office Protocol
                            IMAP  - Internet Message Access Protocol

news reader/server          NNTP  - Network News Transfer Protocol

command line client/server  SSH   - Secure Shell

FTP client/server           FTP   - File Transfer Protocol

Web browser/server          HTTP  - HyperText Transfer Protocol