Protocol

==Protocol is the standard means, rules and conventions which are accepted==. It is the beginning and the core of the web. HTTP is the Hyper Text Transfer Protocol; it is a Web-based protocol. ==It is rules for providing to the web user, and it is a standard delivered to the clients from all common web servers.==

When the web browser wants a user requesting documents, the server changes the document and the web browser converts this document to the appropriate type again. And it's getting sent to the user. ==It therefore serves to transmit files which contain web pages to users based on web protocols.== Human beings made standards that can speak with all of webs. We called these standards a protocol, and when communicate on the web, it can communicate to suit internet protocols.

How Protocol works

The User uses their computer and connects Web server (Google, Yahoo, etc.) through Internet. Consider an example where user trying to access Google:

1. Enter http://www.google.com in the address bar using a web browser.

2. Web browser request information to the Google web server by the HTTP protocols.

3. Web server receives requests, and it sends the answer to the computer.

4. Web browser received the HTTP protocol information represented by texts and pictures.

What is HTTP?

==HTTP or hypertext transfer protocol is an application protocol for distributed, collaborative, hypermedia information systems that allows users to communicate data on the World Wide Web.==

What is the purpose of HTTP?

==HTTP was invented alongside HTML to create the first interactive, text-based web browser: the original World Wide Web==. Today, the protocol remains one of the primary means of using the Internet.

How does HTTP work?

As a request-response protocol, HTTP gives users a way to interact with web resources such as HTML files by transmitting hypertext messages between clients and servers. ==HTTP clients generally use Transmission Control Protocol (TCP) connections to communicate with servers==. HTTP utilizes specific request methods in order to perform various tasks:

GET requests a specific resource in its entirety
HEAD requests a specific resource without the body content
POST adds content, messages, or data to a new page under an existing web resource
PUT directly modifies an existing web resource or creates a new URI if need be
DELETE gets rid of a specified resource
TRACE shows users any changes or additions made to a web resource
OPTIONS shows users which
HTTP methods are available for a specific URL
CONNECT converts the request connection to a transparent TCP/IP tunnel
PATCH partially modifies a web resource

==All HTTP servers use the GET and HEAD methods, but not all support the rest of these request methods.==

Basic aspects of HTTP

HTTP is generally designed to be ==simple and human readable==, even with the added complexity introduced in HTTP/2 by encapsulating HTTP messages into frames and reduced complexity for newcomers.
Introduced in HTTP/1.0, HTTP headers make this protocol easy to extend and experiment with. New functionality can even be introduced by a simple agreement between a client and a server about a new header's semantics.
==HTTP is stateless: there is no link between two requests being successively carried out on the same connection==. This immediately has the prospect of being problematic for users attempting to interact with certain pages coherently, for example, using e-commerce shopping baskets. But while the core of HTTP itself is stateless, HTTP cookies allow the use of stateful sessions. Using header extensibility, HTTP Cookies are added to the workflow, allowing session creation on each HTTP request to share the same context, or the same state.
HTTP and connection is controlled at the transport layer, and therefore fundamentally out of scope for HTTP. ==Though HTTP doesn't require the underlying transport protocol to be connection-based; only requiring it to be reliable, or not lose messages (so at minimum presenting an error)==. Among the two most common transport protocols on the Internet, TCP is reliable and UDP isn't. HTTP therefore relies on the TCP standard, which is connection based.
Before a client and server can exchange an HTTP request/response pair, they must establish a TCP connection, a process which requires several round-trips. The default behavior of HTTP/1.0 is to open a separate TCP connection for each HTTP request/response pair. This is less efficient than sharing a single TCP connection when multiple requests are sent in close succession.

HTTP and TCP/IP

HTTP is a protocol that's built on top of the TCP/IP protocols. ==Each HTTP request is inside an IP packet, and each HTTP response is inside another IP packet--or more typically, multiple packets, since the response data can be quite large==.

Diagram with laptop on left and server on right. Laptop has browser window with "http://www.example.com/index.html" in address bar. Server is labelled with "www.example.com" and its IP address "93.184.216.34". 4 arrows are shown:

First arrow goes from laptop to server and displays packet with HTTP request inside.
Second arrow goes from server to laptop and displays packet with "ACK" inside.
Third arrow goes from server to laptop and displays packet with HTTP response inside.
Fourth arrow goes from laptop to server and displays packet with "ACK" inside.

==There are many other protocols built on top of TCP/IP, like protocols for sending email (SMTP, POP, and IMAP) and uploading files (FTP)==. All of these protocols enable us to use the Internet to connect with other computers in useful ways, and to communicate and collaborate across wide distances.

HTTPS

==HTTPS stands for Hypertext Transfer Protocol over Secure Socket Layer.== Think of it as a secure version of HTTP. HTTPS is used primarily on web pages that ask you to provide personal or sensitive information (such as a password or your credit card details). When you browse a web page using HTTPS, you are using SSL (Secure Sockets Layer).

For a website to use HTTPS it needs to have an SSL certificate installed on the server. These are usually issued by a trusted 3rd party, referred to as a Certificate Authority (CA). When you browse a web page using HTTPS, you can check the details of the SSL certificate. For example, you could check the validity of it. You could also check that the website does actually belong to the organization you think it does. You can usually do this by double clicking on the browser's padlock icon. The padlock icon only appears when you view a secure site