HTTP

1.What is HTTP?

• HyperTextTransferProtocol.
• It is the Communication between the Client & WebServer.
• It takes Requests and Returns Response from server.
• It returns Headers and Body with Every Request.
• It is Stateless means every request is independent(at its core means without cookies.It doesn`t remember anything).

2.What is HTTPS?

• HyperTextTransferProtocolSecure.
• It Encrypts the data in between the transactions(request and response).

• Data is Encrypted using SSL/TLS.

  • SSL stands for Secured Socket Layer.
  • TLS stands for Transport Security Layer.

• Security will be provided by installing an SSL/TLS
  
  certificate on webhost.

3.What are HTTP METHODS?

• When a request is made to server there is a method attached to it.For different purposes different methods will be used.

• GET request:

It mainly used to Fetch data from server like loading a HTML page,loading Json data ,xml data etc...

• POST request:

It used to when adding data to server or posting/sending data to server.

Unlike Get request it doesn`t show the request in URL.

• PUT request:

It used to update the data on the server

• DELETE request:

It used to delete the data on the server

4.What Are HTTP Header Fields?

• HTTP header fields are a list of strings sent and received by both the client program and server on every HTTP request and response. These headers are usually invisible to the end-user and are only processed or logged by the server and client applications.

• There are 3 types of header fields:
  -General header fields
  -Response header fields
  -Request header fields

• General header fields(important Fields in General headers):
  Request URL: URL which is used to make a request
  Request Method:Which HTTP Method is used to make request
  Status Codes: It shows the status of the webpage(It will be explained clearly in the next section)
  Remote Address: IP Address of the computer
  Referral Policy:It controls how much referrer info should be included with request

• Response Headers(important Fields in Response headers):
  Server:The info about who host the server
  Set-cookie:The Set-Cookie HTTP response header is used to send a cookie from the server to the user agent, so that the user agent can send it back to the server later. To send multiple cookies, multiple Set-Cookie headers should be sent in the same response.
  Content-Type:Which type of data is sending from server
  Content-Length:The length of the content

• Request Headers(important Fields in Request headers):
  Cookies:Cookies which sent by request url to Server which are previously stored when server sent them to browser by set-cookies header.
  Accept-xxx:The Support of the browser like accepting encoding of language, Program etc...
  content-type & content-length:Same as response header fields
  Authorization: Sending tokens to Authorize the user.
  User-Agent:The Details of the web-browser of the user.
  Referrer:The Referer header allows a server to identify a page where people are visiting it from.

5.What Are Status Codes?
An HTTP status code is a message a website's server sends to the browser to indicate whether or not that request can be fulfilled.
It has some ranges to indicate the website is working or not.
100-200: INFORMATIONAL
It indicates Request is recieved and It is processing
200-300: SUCCESS
It indicates Request is Successfully recieved,understood and accepted
300-400: REDIRECT
It indicates further action must be taken like redirecting
400-500: CLIENT ERROR
Request error either requested url is not correct or the request is not in the server
500-600:SERVER ERROR
Server Failed to fetch the valid request
Some Commonly Used Status Codes:
200 - Ok
201 - Ok Created
301 - Moved to New Url
304 - Not Modified
400 - Bad Request
401 - Unauthorized
404 - Not Found
500 - Internal Server Error.

6.Difference Between HTTP 1.1 & HTTP 2 ?
HTTP2 is fast,efficient and more secure than HTTP 1.1
In HTTP 1.1 HTML , CSS and Script are requested individually and get response individually whereas in Http2 CSS and Script are requested simultaneously and response also fetched simultaneously.
HTTP2 uses a more advanced compression method called HPACK that eliminates redundant information in HTTP header packets.

                        --THANK YOU--