Appendix B: HTTP Reference

---

Overview

The Hypertext Transfer Protocol (HTTP) is the main protocol underlying web-based communication. Understanding HTTP is important for Java servlet and web application developers since much if not most web-based communication runs over HTTP. HTTP is also extensible, and we can, if required by our web application, extend the protocol for our programs.

HTTP is commonly associated with the browser-to-server communications, but this is only a fraction of its possibilities. We can use HTTP to communicate between applications or applets and our web applications. Using HTTP we can serialise Java objects, raw text, XML data, binary files, and any other data or files. Often company firewalls block almost all communication except that running over the HTTP protocol for security reasons. We can use HTTP tunnelling, which is communication over HTTP to access across a firewall so we can send data between clients and servers.

This appendix will look at the structure and contents of HTTP transactions. We look at client requests and server responses and the various methods available for the requests. We will examine the HTTP headers available and the wide range of responses that the server may return to the client.

We will also include a reference of HTTP status codes and a reference of mime types available.

---