Mac OS X in a Nutshell

Chapter 13. Running Network Services

A network service is a program running on a local machine that other machines can connect to and use over a network. Common examples include web, email, and file-transfer servers.

This chapter builds on the network administration fundamentals covered in Chapter 11 to describe how network services work in general, and how several of the more popular services work on Mac OS X. For information on using these services client-side, consult Chapter 7.

Network Services Overview

Generally, a network service operates through a daemon program that listens for incoming connections on a certain port—web servers usually listen on port 80, for example, and ssh connections typically happen on port 22. (The precise way it accomplishes this is implementation-specific; it might choose to handle the whole connection itself, or fork off another process to handle it so the daemon can get back to listening.)