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Hypertext Transfer Protocol

HTTP stands for Hypertext Transfer Protocol. It's a stateless, application-layer protocol for communicating between distributed systems, and is the foundation of the modern web. As a web developer, we all must have a strong understanding of this protocol.
Let us review this protocol through the lens of a web developer. We will tackle the topic in two parts. In this first entry, we'll cover the basics and outline the various request and response headers. In the follow-up article, we will review specific pieces of HTTP, namely caching, connection handling and authentication. It is best to instead consult the RFC (RFC 2616) for in-depth coverage. I will be pointing to specific parts of the RFC throughout the article.

HTTP Basics

HTTP allows for communication between a variety of hosts and clients, and supports a mixture of network configurations.
To make this possible, it assumes very little about a particular system, and does not keep state between different message exchanges. This makes HTTP a stateless protocol. The communication usually takes place over TCP/IP, but any reliable transport can be used. The default port for TCP/IP is 80, but other ports can also be used.

TCP/IP Protocols For the Web

  1. Web browsers and servers use TCP/IP protocols to connect to the Internet. Common TCP/IP protocols are:
  2. HTTP - Hyper Text Transfer Protocol: HTTP takes care of the communication between a web server and a web browser. HTTP is used for sending requests from a web client (a browser) to a web server, returning web content (web pages) from the server back to the client.
  3. HTTPS - Secure HTTP: HTTPS takes care of secure communication between a web server and a web browser. HTTPS typically handles credit card transactions and other sensitive data.
  4. FTP - File Transfer Protocol: FTP takes care of transmission of files between computers.

Web Protocols

Application, Presentation, Session 1) Transport 2) Network 3) Datalink 4) Physical

HTTP and the Gopher Web protocol operate at the Application layer of the OSI Model.

Telnet and the NNTP Web protocol operate at the presentation layer of the OSI model.