ABSTRACT
This chapter describes how application programs use Transmission Control Protocol/Internet Protocol software to provide services across the Internet. It examines that, despite their diversity, all applications on the Internet follow a single organizational model. The Internet offers an amazing set of services with diverse styles of interaction. In some cases, two humans interact. In other cases, a human interacts with a remote computer program that supplies information. Despite the wide diversity among Internet services and apparent differences among them, the software that implements a service always follows a single approach known as client-server computing. Users typically wait until they need a service before launching a client app that accesses the service. A server app does wait to run until it’s needed because a client will not be able to access the service unless the server app is already running, waiting for a client to contact it.
