Web Requests

HyperText Transfer Protocol (HTTP)

Internet communication uses the protocol HTTP which is an application level-protocol. HTTP is client - server based communciation using requests.

DNS

DNS is used to resolve domain names to get its matching IP. After getting the IP a GET request is send asking for root path, result in a 200 OK code when a file is found.

HTTP sents everything in cleartext while HTTPS sends all communications in encrypted formats.

Requests and Responses

HTTP request is from client, containing details required from a server like resources, request data and headers. The server proceses and sends a HTTP response.

Request Headers

Headers are used to pass information between client and server, some are specific and some general.

Header	Example
Date	Date: Wed, 12 May 2022 11:32:42 GMT
Connection	Connection: close
Content-Type	Content-Type: text/html
Content-Length	Content-Length: 385
Content-Encoding	Content-Encoding: gzip
Host	Host: www.domain.com
User-Agent	User-Agent: curl/7.77.0
Cookie	Cookie: PHPSESSID=b4e4fbd93540

Response Headers

Header	Example
Server	Server: Apache/2.2.14 (Win32)
Set-Cookie	Set-Cookie: PHPSESSID=b4e4fbd93540
Content-Security-Policy	Content-Security-Policy: script-src 'self'
Referrer-Policy	Referrer-Policy: origin

HTTP Methods

Methods are used to tell server how to process requests we send and how to reply.

Method	Description
GET	Requests resource.
POST	Sends data to server
HEAD	Requests headers
PUT	Creates new resource on server
DELETE	Deletes resource on server
OPTIONS	Show accpted methods
PATCH	Applies modifications to resource

Reponse Codes

HTTP status codes tells client the status of a request. Most common are.

Code	Description
200 OK	Succesfull request
302 Found	Redirect to another URL
400 Bad Request	Returns malformed request
403 Forbidden	No access to resource
404 Not Found	Doesn't exist
500 Interal Server Error	Server cannot process request.