Previously, we said that a RESTful service is based on the HTTP protocol. This is a rather complex protocol, but its most important parts are quite simple. Here is a simplified version of it.
The protocol is based on a pair of messages. First, the client sends a request to the server, and after the server receives this request, it replies by sending a response to the client. Both messages are in American Standard Code for Information Interchange (ASCII) text, and so they are easily manipulated.
The HTTP protocol is usually based on the TCP/IP protocol, which guarantees that these messages arrive at the addressed process.
Let's see a typical HTTP request message, as follows:
GET /users/susan/index.html HTTP/1.1
Host: www.acme.com
Accept: image/png, image/jpeg, */*
Accept-Language: en-us
User-Agent: Mozilla/5.0
This message contains six lines because there is an empty line at the end.
The first line begins with the word GET. This word is the method...