The document outlines the basic structure of web architecture, highlighting the roles of the client (browser) and server. It explains HTTP communication, including request methods, response status codes, and the importance of statelessness, along with solutions like cookies and sessions. Additionally, it provides examples of HTTP requests and responses while noting the common technologies used on both client and server sides.

1. Basic Web Architecture
and REST Api Calls

2. The WEB APP
The web is a two-tiered architecture
● A web browser (The Client) that displays information.
● A web server that transfers information to the client

3. The Technologies
● On Client Side: HTML, CSS, JavaScript ...
● On Server Side: PHP, JavaScript, Java …
Their common knowledge is made mainly of URI and HTTP
● the URI (Universal Resource Identifier) has 4 parts: the protocol type, web
server domain, folder path (optional), web page HTML file (optional)
● HTTP (HyperText Transfer Protocol) is a request/response standard of a
client and a server.

4. How it works
● An HTTP client initiates a request
● Resources to be accessed by HTTP are identified using URIs
The request message consists of the following:
● Request line
● Headers
● An optional message body

5. Request Methods
The HTTP methods, also known as “verbs” are:
● HEAD
● GET
● POST
● PUT
● DELETE
● TRACE
● OPTIONS
● CONNECT

6. Safe Methods
● HEAD, GET, OPTIONS and TRACE are defined as safe (they only retrieve
information)
● POST, PUT, DELETE are intended for actions on your data

7. HTTP response
The first line of the HTTP response is called the STATUS LINE. Status Code is
part of it.
● Success: 2xx
● Redirection: 3xx
● Client-Side Error: 4xx
● Server-Side Error: 5xx
Examples: 200, 202, 301, 304, 404, 500

8. Client Request Example :D
● Request Line: POST localhost:8080/users/login
● Headers: Content-Type: application/json
● Body:
{
"email": "ralu.mihordea@ultragrup.ro",
"password": "ltMrQyX4"
}

9. Server Response Example
Status Line: 200 Ok
Body:
{
"status": true,
"errorMessage": "",
"payload": {
"userAuthToken": "eyJ0eXukhJev2iFRibQq09VWIS9Ap_rpiTc"
}
}

10. HTTP session state
● HTTP is a stateless protocol
● Hosts do not need to retain information about users between requests.
● Statelessness is a scalability property
● Solutions to this:
○ Cookies
○ Sessions

11. Cookie
● Cookie is a small piece of text stored on a user’s computer by a web browser
● A cookie consists of one or more name-value pairs containing infos like user
preferences
● Commonly used for: authenticating, shopping cart items, session tracking and
remembering specific information about users

12. Session
● server side storage of information
● persists throughout the user’s interaction with the site
● only a unique identifier is stored on the client (session id)
● For each HTTP request the session id is passed. The site pairs this session id
with it’s internal database and retrieves the stored variables for use by the
requested page.

13. Bibliography
● http://www.lassosoft.com/Tutorial-Understanding-Cookies-and-Sessions
● http://www.slideshare.net/cchamnap/introduction-to-web-architecture?qid=08
4fc228-f93f-4f32-ba77-cd827bacd537&v=&b=&from_search=1