What is HTTP?

HTTP stands for Hypertext Transfer Protocol, and it is used for communication between browsers, servers, and applications.

 

Here are the components of HTTP:

MIME(Multipurpose Internet Mail Extensions) 

MIME is used to distinguish between different data types on the internet, as it deals with a wide variety of data types.

 

URI(Uniform Resource Identifier) 

• It allows us to specify the location of a resource.
• For example, "http://www.naver.com/image.gif" means "go to naver.com and get image.gif using the HTTP"
• url(uniform resource location): It specifies specific location of a resource. 
• urn(uniform resource name): It specifies specific name of a resouce regardless of location. 

Most of URIs are URLs . 

Transaction

• It consists of a request (from the web browser to the server) and a response (from the server to the web browser).
• "Status codes" are used for communication.
• A web page can be composed of several objects, which means many requests may be needed.

Message

• start line : the start line typically includes the HTTP method (e.g., GET, POST), the target URI (Uniform Resource Identifier), and the HTTP version being used.
• header : headers include Content-Type, Content-Length, User-Agent, and Host.
• body: In requests, the body often carries data submitted by the client, while in responses, it contains the requested information or data.

Tcp connection 

• TCP is a lower-level concept in networking compared to HTTP.
• A TCP connection is established first, and then HTTP communication occurs.
• The following sequence is followed:
  • The web browser extracts the host name from the URL and translates it into an IP address.
  • The web browser finds the port number in the URL (if available).
  • The web browser establishes a TCP connection with the web server.
  • The web browser can communicate with the web server at the HTTP level. 

This article is based on "http definitive guide".