[HTTP] Web Communication through Request and Response

1) Role: Communication between web servers & clients

2) Two message types: HTTP Requests / Responses

• Client sends HTTP request to server and server sends HTTP response

Loading pages, form submit, Ajax calls

3) HTTP is stateless. What does that mean?

• Every request is completely independent (each request is a single transaction).
• Programming, Local Storage, Cookies, Sessions are used to create enhanced user experiences.

4) What is HTTPS?

1) HTTPS (Hyper Text Transfer Protocol Secure)

2) Data sent is encrypted

3) SSL (HTTPS protocol is running on SSL protocol, just the way web is working on the Internet. Advantages of SSL and SSL digital certificate are:

• Deter hackers from eavesdropping communication content
• Ensure that the site client is accessing is secure
• Prevent distortion of communication content

4) Install certificate on web host

5) HTTP Requests and Responses are composed of

1. A start-line describing the requests to be implemented, or its status of whether successful or a failure. This start-line is always a single line.

2. An optional set of HTTP headers specifying the request, or describing the body included in the message.

3. A blank line indicating all meta-information for the request have been sent.

4. An optional body containing data associated with the request (like content of an HTML form), or the document associated with a response. The presence of the body and its size is specified by the start-line and HTTP headers.

6) The start line of HTTP request is composed of three elements.

6.1) An HTTP method (GET, PUT, POST, DELETE). GET and POST are widely used.

• GET: Retrieve data from the server
• POST: Submit data to the server
• PUT: Update data already on the server
• DELETE: Deletes data from the server

6.2) Request Target:

In order to understand request target, you should be familiar with Endpoints and API. People including myself are even more confused about complicated explanations. I’m going to add links about Endpoints and API, very simple and to the point.

• https://stackoverflow.com/questions/2122604/what-is-an-endpoint#47573997
• https://smartbear.com/learn/performance-monitoring/api-endpoints/

6.3) HTTP Version:

• HTTP/1.1

7) HTTP General Headers:

• Request URL: url reqeust
• Request Method: get request and post request
• Status Code: 200
• Remote Address: IP of remote control

8) HTTP General Response:

• Server: Most of time, it is hidden to prevent hackers from knowing what types of server the website is using.
• Set-Cookie:Set-Cookie is used for servers to send a small piece of data called cookies from client to server
• Content-Type: text/css, te xt/html, image/png, application/json
• Content-Length: 8bit bite

9) Request:

• Cookies: Temporary internet files
• Authorization: HTTP is stateless, so you need some type of token within the Header for verification
• User-Agent: Mozilla or Chrome

10) HTTP Status Code

1xx: informational

Request received / receiving

2xx: Success

Successfully Received, understood and accepted

3xx: Redirect

Further action must be taken / redirect

4xx: Client Error

Request does not have what it needs

5xx: Server Error

Server failed to fulfill an apparent valid request

11) Widely known status code

• 200 - OK
• 201 - OK created
• 301 - Moved to new URL
• 304 - Not modified (Cached version)
• 400 - Bad request
• 401 - Unauthorized (missing tokens)
• 404 - Not found
• 500 - Internal server error

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