Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. HTTP Body Data is the data bytes transmitted in an HTTP transaction message immediately following the headers if there is any (in the case of HTTP/0.9 no headers are transmitted). The Hypertext Transfer Protocol (HTTP) is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. HTTP functions as a request-response protocol in the client-server computing model. In HTTP, a web browser, for example, acts as a client, while an application running on a computer hosting a web site functions as a server. The client submits an HTTP request message to the server. The server, which stores content, or provides resources, such as HTML files and images, or generates such content on the fly, or performs other functions on behalf of the client, returns a response message to the client. A response contains completion status information about the request and may contain any content requested by the client in its message body.