Java Network Programming, Second Edition

Chapter 3. Basic Web Concepts

By the time you finish this book, I hope you will realize that Java can do a lot more than create flashy web pages. Nonetheless, many of your programs will be applets on web pages or will need to talk to web servers to retrieve files or post data. Therefore, it’s important to have a solid understanding of the interaction between web servers and web browsers.

The Hypertext Transfer Protocol (HTTP) is a standard that defines how a web client talks to a server and how data is transferred from the server back to the client. HTTP relies heavily on two other standards: the Multipurpose Internet Mail Extensions (MIME) and the Hypertext Markup Language (HTML). MIME is a way to encode different kinds of data, such as sound and text, to be transmitted over a 7-bit ASCII connection; it also lets the recipient know what kind of data has been sent, so that it can be displayed properly. As its name implies, MIME was originally designed to facilitate multimedia email and to provide an encoding that could get binary data past the most brain-damaged mail transfer programs. However, it is now used much more broadly. HTML is a simple standard for describing the semantic value of textual data. This means that you can say “this is a header”, “this is a list item”, “this deserves emphasis”, and so on, but you can’t specify how headers, lists, and other items are formatted: formatting is up to the browser. HTML is a “hypertext markup language” because it includes a way to ...