Acceptable Link Format

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The Acceptable Link Format, also known as HTTP, is an internet protocol used to transmit data over the web. It is the standard format for accessing websites, reading documents, and downloading files from the internet.

History of HTTP

HTTP was invented in 1989 by Jon Postel and implemented by the Internet Engineering Task Force (IETF). The first version of HTTP, known as HTTP/0.9, was released in October 1991. Since then, HTTP has undergone numerous revisions, with each new version introducing new features and improvements.

HTTP Version Structure

The structure of an HTTP request is defined by the following components:

  • Method: The HTTP method used to send data over the Connection. Common methods include GET, POST, PUT, DELETE, HEAD, OPTIONS, and PATCH.
  • URL: A unique identifier for a resource on a web server.
  • Headers: Optional metadata associated with a request or response.
  • Query String: An unordered collection of key-value pairs appended to the URL.

HTTP Request Method

The HTTP Request Method is used to indicate the action that should be performed on the target resource. The most common methods are:

  • GET: Retrieve a resource from the server.
  • POST: Send data to the server, which can create or update resources.
  • PUT: Update an existing resource with new data.
  • DELETE: Delete a resource.

HTTP Request URL

The HTTP request URL is the unique identifier for a resource on a web server. It consists of:

  • A protocol (HTTP/1.x)
  • A domain name or IP address
  • An optional path, query string, and fragment

HTTP Response Format

An HTTP response is used to provide information about the outcome of an HTTP request. The response includes:

  • Status Code: A three-digit code indicating the status of the request (e.g., 200 OK).
  • Headers: Optional metadata associated with the response.
  • Body: The content of the response.

HTTP Status Codes

HTTP Status Codes are used to indicate the outcome of an HTTP request. They are defined by the IETF and consist of a three-digit code followed by a brief description:

Status Code Description
200 OK Request was successful.
404 Not Found Resource not found.
500 Internal Server Error Server error.

HTTP Headers

HTTP Headers provide metadata about an HTTP response. They are used to customize the behavior of the client and server.

Common HTTP Headers

  • <a href="/Content-Type" class="missing-article">Content-Type</a>: Specifies the media type of a resource.
  • <a href="/Accept" class="missing-article">Accept</a>: Specifies the types of resources that a client can handle.
  • <a href="/Cache-Control" class="missing-article">Cache-Control</a>: Controls caching behavior on both the client and server.
  • [Connection](/Connection): Specifies the Connection mode (e.g., keep-alive).

HTTP Query Strings

HTTP query strings are used to pass data from one resource to another. They consist of:

  • Key-Value Pairs: Data is separated by spaces or semicolons.

Example HTTP Request and Response

Here’s an example of a GET request for the Wikipedia homepage:

GET https://en.wikipedia.org/wiki/HTTP HTTP/1.1
Host: wikipedia.org
<a href="/Accept" class="missing-article">Accept</a>: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

<a href="/User-Agent" class="missing-article">User-Agent</a>: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.37

And here’s an example of the response from Wikipedia:

HTTP/1.1 200 OK
<a href="/Content-Type" class="missing-article">Content-Type</a>: text/html; charset=UTF-8

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Wikipedia</title>
    <style>.wikitable tbody tr th, .wikitable tbody td {border-bottom: 1px solid #ccc;} .wikitable tbody tr:nth-child(n+2) td::after {content-" &gt; ";}</style>
</head>
<body>
    <h1>Wikipedia</h1>
    <p>This is a test page.</p>
</body>
</html>

HTTP Methods

HTTP Methods are used to interact with web resources. The most common methods are:

  • GET: Retrieve a resource from the server.
  • POST: Send data to the server, which can create or update resources.
  • PUT: Update an existing resource with new data.

HTTP Response Status Codes

HTTP Response Status Codes indicate the outcome of an HTTP request. They are defined by the IETF and consist of a three-digit code followed by a brief description:

Status Code Description
200 OK Request was successful.
404 Not Found Resource not found.
500 Internal Server Error Server error.

HTTP Headers

HTTP Headers provide metadata about an HTTP response. They are used to customize the behavior of the client and server.

Common HTTP Headers

  • <a href="/Content-Type" class="missing-article">Content-Type</a>: Specifies the media type of a resource.
  • <a href="/Accept" class="missing-article">Accept</a>: Specifies the types of resources that a client can handle.
  • <a href="/Cache-Control" class="missing-article">Cache-Control</a>: Controls caching behavior on both the client and server.
  • [Connection](/Connection): Specifies the Connection mode (e.g., keep-alive).

Conclusion

HTTP is an essential technology for accessing and sharing information over the internet. Its structure, status codes, headers, and methods define how requests are formatted and responses are generated. By understanding HTTP, developers can build robust web applications and services that interact with web resources efficiently.