HTTP:
Ø  It is Hyper Text Transfer Protocol
Ø  It is an application-level protocol for distributed, collaborative, hypermedia information systems.
Ø  This is the foundation for data communication for the World Wide Web (i.e. internet) since 1990.
Ø  HTTP is a generic and stateless protocol which can be used for other purposes as well using extensions of its request methods, error codes, and headers.
Ø  Basically, HTTP is a TCP/IP based communication protocol, that is used to deliver data (HTML files, image files, query results, etc.) on the World Wide Web.
Ø  The default port is TCP 80, but other ports can be used as well.
Ø  It provides a standardized way for computers to communicate with each other.
Ø  HTTP specification specifies how clients' request data will be constructed and sent to the server, and how the servers respond to these requests.

Basic Features

Ø  There are three basic features that make HTTP a simple but powerful protocol:
·      HTTP is connectionless: The HTTP client i.e. a browser initiates an HTTP request and after a request is made, the client disconnects from the server and waits for a response. The server processes the request and re-establishes the connection with the client to send a response back.
·      HTTP is media independent: It means, any type of data can be sent by HTTP as long as both the client and the server know how to handle the data content. It is required for the client as well as the server to specify the content type using appropriate MIME-type.
·      HTTP is stateless: As mentioned above, HTTP is connectionless and it is a direct result of HTTP being a stateless protocol. The server and client are aware of each other only during a current request. Afterwards, both of them forget about each other. Due to this nature of the protocol, neither the client nor the browser can retain information between different requests across the web pages.


Ø  The HTTP protocol is a request/response protocol based on the client/server based architecture where web browsers, robots and search engines, etc. act like HTTP clients, and the Web server acts as a server.
          Client:
Ø  The HTTP client sends a request to the server in the form of a request method, URL, and protocol version, followed by a MIME-like message containing request modifiers, client information, and possible body content over a TCP/IP connection.
Ø  (Note: One can classify URIs as locators (URLs), or as names (URNs), or as both. A Uniform Resource Name (URN) functions like a person’s name, while a Uniform Resource Locator (URL) resembles that person’s street address. In other words: the URN defines an item’s identity, while the URL provides a method for finding it.)
          Server:
Ø  The HTTP server responds with a status line, including the message's protocol version and a success or error code, followed by a MIME-like message containing server information, entity meta information, and possible entity-body content.
Ø  HTTP protocol is similar to FTP because it transfers files and uses the services of TCP. However, it is much simpler than FTP because it uses only one TCP connection. There is no separate control connection; only data is transferred between the client and the server.
Ø   HTTP protocol is like SMTP protocol because the data transferred between the client and the server look like SMTP messages. In addition, MIME-like headers control the format of the messages. However, HTTP differs from SMTP in the way the messages are sent from the client to the server and from the server to the client. Unlike SMTP, the HTTP messages are not destined to be read by humans; they are read and interpreted by the HTTP server and HTTP client (browser). SMTP messages are stored and forwarded, but HTTP messages are delivered immediately.

What is an HTTP request?

Ø  A Http request message consists of a request line, headers and sometimes a body.
An HTTP request is a way that web browsers ask for information to load website pages. HTTP request contains HTTP version type, a URL, HTTP request headers and HTTP body.
HTTP request Headers: HTTP request headers include text information saved in key-value pairs and these are contained in every HTTP request.
URL: A client that wants to access a document needs an address. To facilitate the access of documents distributed throughout the world, HTTP protocol uses the concept of locations. The World Wide Web uses a locator called a URL to identify and intertribal data.
URL is called as (Uniform Resource Locator). A URL is an internet address of any website in common format http://ecomputernotes.com, A URL has three parts: Method: //Host/Path. which is used for accessing any file, document or website.

          What is an HTTP response?

Ø  An HTTP response means when the web client gets the answer back from the web server. It contains the information that was asked for in the HTTP request. HTTP response contains an HTTP status code, HTTP response headers, and HTTP body.
HTTP status codes: Many times when a client sends a request to the server and If the HTTP request is not correct then the error comes. These errors are shown in numeric codes. These are also called as HTTP status codes. These status codes are given by the server to identify the problem. Some common codes are shown below.
1.401-“Unauthorized”
2.400-“Bad request”
3.404-“File not found”

What is HTTPS?

Ø  HTTPS is a Hyper Text Transfer Protocol Secure. This is the secure version of HTTP Protocol. HTTPS means a secure layer between client and server. HTTPS encrypted our data by Transport Security Layer (TLS). HTTPS is a sign of security most of the websites are secured with HTTPS.


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