Everything You Need to Know About HTTP (Hypertext Transfer Protocol)

The purpose of HTTP is to fetch the resources a client requests. 

Here's an example of the request-response cycle between a client and a server:

1. The client and the server computers must be connected via an Internet connection.

2. When the connection is established, the client requests to access a resource via an HTTP message.  

3. As HTTP is a connectionless protocol, the client disconnects from the server, waiting for a response. 

4. The server processes the request. It prepares the response, reestablishes the connection, and sends back the response via an HTTP message. 

5. The client receives the message.

6. The two computers disconnect. 

If we use human language to explain the process, it would go something like this:

• You: I want to see your Customer Service page.
• The server: Okay, got it. It's coming right away.

Or, if there's an error:

• You: I want to see your Customer Service page. 
• The server: I'm sorry, I can not find the page you're requesting. 

HTTP messages are sent in a format that's similar to the format used by the Internet mail and the Multipurpose Internet Mail Extensions.

A typical HTTP message has three main sections: the start line, the headers, and the body. Generally, the three sections are plain text and are easy to read. 

The information of the HTTP message varies, depending on whether it's a request or a response. 

Requests consist of the following elements:

• the HTTP method that tells the server what to do, usually a verb like GET or POST

• the URL of the resource stripped from elements that are obvious from the context

• the version of the HTTP protocol

• optional headers 

Responses consist of the following elements:

• the version of the HTTP protocol

• a status code, such as a redirect, client error, or server error

• a status message that contains a short description of the status code

• HTTP headers

• a body containing the fetched resource, but this is optional

HTTP response status codes are contained in the HTTP message that's sent from the server to the client. They tell whether an HTTP request has been successfully completed or there was some type of error. 

There are five main classes:

• 1xx: Informational responses 

• 2xx: Successful responses

• 3xx: Redirects 

• 4xx: Client errors 

• 5xx: Server errors

To sum up, the main things we can learn from this article are:

• HTTP stands for Hypertext Transfer Protocol. It's the standard protocol that defines how messages are formatted and sent across the web.

• In a sense, HTTP acts as a messenger of the web. It delivers messages from the client to the server, and vice versa.

• The three important aspects of HTTP is that it is connectionless, stateless, and can deliver any kind of data. 

• The purpose of HTTP is to fetch the resources a client requests. 

• A typical HTTP message has three main sections: the start line, the headers, and the body.

• There are different types of HTTP response status codes. They all indicate whether a specific HTTP request has been successfully completed. There are five classes, including 1xx, 2xx, 3xx, 4xx, and 5xx status codes. 

• If HTTP stood for Hypertext Transfer Protocol, HTTPs stands for Hypertext Transfer Protocol Secure. The difference is that HTTPS transmits its data security using an encrypted connection.