Chapter 32. The Hypertext Transfer Protocol

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

The Beginning of HTTP 628

Defining HTTP 629

URLs, URIs, and URNs 630

The Internet is certainly familiar to readers of this book. Web pages are coded using the Hypertext Markup Language (HTML), as well as Java, ASP, and many other technologies. Underlying all of these technologies is an Application layer protocolthe Hypertext Transfer Protocol (HTTP). HTTP is the underlying application protocol that is used to deliver Web pages to your browser. Like other protocols (FTP, Telnet, and others) the transport protocol for HTTP is usually the TCP/IP suite of protocols, using port 80. HTTP can be sent over other network protocols, but that option is rarely used today. Port 80 is not a requirement for HTTP. Other ports can be used, and often are. To specify a different port, use a colon character (:) at the end of the URL, followed by the port number. However, in the original RFC specification for HTTP, port 80 was used.

To learn about the basics of TCP/IP, ports, and related protocols and applications, see Chapter 24, "Overview of the TCP/IP Protocol Suite."

The protocols TCP and IP were developed long before HTTP was created. HTTP, like other application protocols, is transmitted on the network using TCP/IP as the underlying protocol to ensure a timely, reliable transport.

Yet HTTP is the protocol that is placed between HTML and TCP/IP. Keep in mind that HTML is just a language used for creating Web pages. HTTP is used to transfer these pages to end users, and HTTP is transported across the Internet using TCP/IP.

This chapter is not going to help you learn the many versions of HTML, or other programming languages (such as Java and C#). Instead, you will learn about HTTP.

Note

HTTP is currently defined by version 1.1. In this chapter you will learn about some of the history of HTTP, including the concepts presented by the original version as well as HTTP v.1.1.