HTTP is a text-based client-server protocol that runs over TCP. Plain HTTP runs over TCP port 80.
It should be noted that plain HTTP is mostly deprecated for security reasons. Today, sites should use HTTPS, the secure version of HTTP. HTTPS secures HTTP by merely running the HTTP protocol through a Transport Layer Security (TLS) layer. Therefore, everything we cover in this chapter regarding HTTP also applies to HTTPS. See Chapter 9, Loading Secure Web Pages with HTTPS and OpenSSL, for more information about HTTPS.
HTTP works by first having the web client send an HTTP request to the web server. Then, the web server responds with an HTTP response. Generally, the HTTP request indicates which resource the client is interested in, and the HTTP response delivers the requested resource.
Visually, the transaction is illustrated in the following graphic:
The preceding...
