HTTP Messages

Request Message #

start-line : request-line / status-line
request-line = method SP(space) request-target(Path=request target) SP HTTP-version CRLF(enter)

HTTP Methods (GET for retrieval) #

Types : GET , POST , PUT, DELETE.. Specifies the action the server should perform

GET : Retrieve a resource
POST : Process request body

Request Target (/search?p=hello&hl=ko) #

absolute-path[?query] absolute path[query] Absolute path = a path starting with "/" Note: There are other types of path specification methods, such as *, http://...?x=y.

HTTP version #

Response Message #

start-line = request-line / status-line
status-line = HTTP-version SP status-code SP reason-phrase CRLF
HTTP Version
HTTP Status Code: Indicates request success or failure 200: Success 400: Client request error 500: Server internal error

Reason Phrase: A short, human-readable description of the status code

HTTP Headers #

header-field = field-name ":" OWS field-value OWS (OWS:whitespace allowed) field-name is case-insensitive

HTTP Request Message #

GET/search?=q=hello&hl=ko HTTP/1.1 Host : www.google.com

HTTP Response Message #

HTTP/1.1 200 OK Content-Type : text/html;charset=UTF-8 Content-Length : 3423

Purpose

All additional information required for HTTP transmission
e.g. message body content, message body size, compression, authentication, request client (browser)
Too many standard headers
Can add arbitrary headers if needed
e.g. helloworld: hihi

HTTP Message Body #

Purpose

Actual data to be transmitted
Can transmit all data that can be represented as bytes, such as HTML documents, images, videos, JSON, etc.

Simple and extensible

HTTP is simple, its spec is worth reading..
HTTP messages are also very simple.
Highly successful standard technologies are simple yet extensible.

HTTP Summary #

Everything is transmitted in HTTP messages
HTTP History: Learn based on HTTP/1.1
Client-server architecture
Stateless protocol
HTTP Messages
Simple, extensible
This is the era of HTTP