HTTP message structure
HTTP is based on the client/server (C/S) architecture model. It exchanges information through a reliable link and is a stateless request/response protocol.
An HTTP "client" is an application (a web browser or any other client) that connects to a server for the purpose of sending one or more HTTP requests to the server.
HTTP uses Uniform Resource Identifiers (URI) to transmit data and establish connections.
Once the connection is established, data messages are sent using a format similar to that used by Internet mail [RFC5322] and Multipurpose Internet Mail Extensions (MIME) [RFC2045].
Client request message
The request message that the client sends an HTTP request to the server includes the following format: request line, request header It consists of four parts (header), blank line and request data. The following figure shows the general format of the request message.
Server response message
HTTP response also consists of four parts, namely: status line, message header, blank line and response body.
Example
The following example is a typical example of using GET to transfer data:
Client Request:
GET /hello.txt HTTP/1.1 User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3 Host: www.example.com Accept-Language: en, mi
Server response:
HTTP/1.1 200 OK Date: Mon, 27 Jul 2009 12:28:53 GMT Server: Apache Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT ETag: "34aa387-d-1568eb00" Accept-Ranges: bytes Content-Length: 51 Vary: Accept-Encoding Content-Type: text/plain
Output result:
Hello World! My payload includes a trailing CRLF.
