Web Requests

👉 Overview

👀 What ?

A web request is a fundamental concept in web programming and network communication. It is a message that a client sends to a server requesting a specific service or information. Typically, this request is made over HTTP or HTTPS protocols. The client could be a web browser, and the server could be a web server hosting a website or a web service.

🧐 Why ?

Understanding web requests is crucial for several reasons. Firstly, every interaction between a client and a server on the web relies on web requests. Whether you're loading a web page, submitting a form, or interacting with a web service, you're making a web request. Secondly, understanding web requests is essential for diagnosing and fixing issues with web applications or services. Thirdly, understanding web requests is vital for web security. By understanding how web requests work, you can better protect your applications and services from potential attacks.

⛏️ How ?

To make a web request, a client must specify several pieces of information: the method (GET, POST, etc.), the URL, any headers, and possibly a body (for POST requests). This information is packaged into a specific format and sent to the server. The server then reads the request, processes it, and returns a response. This response contains a status code, any headers, and possibly a body (which contains the requested resource or information).

⏳ When ?

Web requests have been used since the inception of the World Wide Web in the early 1990s. They are a fundamental part of the HTTP protocol, which was first defined in 1991.

⚙️ Technical Explanations

At a low level, a web request is simply a text message sent over a network connection. Here's a more detailed breakdown of what you need to know about web requests:

Request Line

• Method: This specifies the action to be performed. The most common methods are GET (retrieve data), POST (submit data), PUT (update data), DELETE (remove data), and HEAD (retrieve headers only).
• URL: This specifies the resource being requested. It includes the protocol (http or https), the domain name, and the path to the resource.
• HTTP Version: This specifies the version of the HTTP protocol being used, such as HTTP/1.1 or HTTP/2.

Headers

Headers provide additional information about the request. Common headers include:

• Host: Specifies the domain name of the server (for virtual hosting).
• User-Agent: Provides information about the client software making the request.
• Accept: Specifies the media types that the client is willing to receive.
• Content-Type: Indicates the media type of the body of the request (for POST and PUT requests).
• Authorization: Contains credentials for authenticating the client with the server.

Body

For methods like POST and PUT, the body contains the data being sent to the server. This can be in various formats, such as JSON, XML, or form data.

Server Response

The server's response to a web request follows a similar structure:

• Status Line: This includes the HTTP version, a status code, and a status message. Common status codes include:
  • 200 OK: The request was successful.
  • 201 Created: The request was successful, and a new resource was created.
  • 400 Bad Request: The server could not understand the request due to invalid syntax.
  • 401 Unauthorized: The client must authenticate itself to get the requested response.
  • 404 Not Found: The server can not find the requested resource.
  • 500 Internal Server Error: The server encountered an unexpected condition.
• Response Headers: These provide additional information about the response. Common headers include:
  • Content-Type: Indicates the media type of the body of the response.
  • Content-Length: Indicates the size of the body of the response.
  • Set-Cookie: Sends cookies from the server to the client.
• Response Body: If the response includes a body, it contains the resource or information requested. This can be in formats like HTML, JSON, XML, etc.

Additional Concepts

• Cookies: Small pieces of data sent from the server and stored on the client, used for session management, tracking, and personalization.
• Caching: Mechanisms to store copies of web resources to reduce latency and server load. Headers like Cache-Control and Expires control caching behavior.
• Security: HTTPS is used to encrypt web requests and responses, ensuring data integrity and confidentiality. Headers like Strict-Transport-Security enforce the use of HTTPS.

Understanding these components and how they interact is essential for diagnosing issues, optimizing performance, and securing web applications.

At a low level, a web request is simply a text message sent over a network connection. Here's a more detailed breakdown of what you need to know about web requests, along with a detailed example:

Request Line

• Method: This specifies the action to be performed. The most common methods are GET (retrieve data), POST (submit data), PUT (update data), DELETE (remove data), and HEAD (retrieve headers only).
• URL: This specifies the resource being requested. It includes the protocol (http or https), the domain name, and the path to the resource.
• HTTP Version: This specifies the version of the HTTP protocol being used, such as HTTP/1.1 or HTTP/2.

Example

Let's consider an example where you make a GET request to retrieve data from a JSON placeholder API.

curl -X GET "<https://jsonplaceholder.typicode.com/posts/1>"

Breakdown

• Method: GET
• URL: https://jsonplaceholder.typicode.com/posts/1
• HTTP Version: Not explicitly mentioned in curl, but typically HTTP/1.1

Headers

Headers provide additional information about the request. Common headers include:

• Host: Specifies the domain name of the server (for virtual hosting).
• User-Agent: Provides information about the client software making the request.
• Accept: Specifies the media types that the client is willing to receive.
• Content-Type: Indicates the media type of the body of the request (for POST and PUT requests).
• Authorization: Contains credentials for authenticating the client with the server.

Example

curl -X GET "<https://jsonplaceholder.typicode.com/posts/1>" \\
     -H "User-Agent: curl/7.68.0" \\
     -H "Accept: application/json"

Breakdown

• User-Agent: curl/7.68.0
• Accept: application/json

Body

For methods like POST and PUT, the body contains the data being sent to the server. This can be in various formats, such as JSON, XML, or form data.

Example

Let's consider an example where you make a POST request to add a new post.

curl -X POST "<https://jsonplaceholder.typicode.com/posts>" \\
     -H "Content-Type: application/json" \\
     -d '{"title": "foo", "body": "bar", "userId": 1}'

Breakdown

• Method: POST
• URL: https://jsonplaceholder.typicode.com/posts
• Content-Type: application/json
• Body: {"title": "foo", "body": "bar", "userId": 1}

Server Response

The server's response to a web request follows a similar structure:

• Status Line: This includes the HTTP version, a status code, and a status message. Common status codes include:
  • 200 OK: The request was successful.
  • 201 Created: The request was successful, and a new resource was created.
  • 400 Bad Request: The server could not understand the request due to invalid syntax.
  • 401 Unauthorized: The client must authenticate itself to get the requested response.
  • 404 Not Found: The server can not find the requested resource.
  • 500 Internal Server Error: The server encountered an unexpected condition.
• Response Headers: These provide additional information about the response. Common headers include:
  • Content-Type: Indicates the media type of the body of the response.
  • Content-Length: Indicates the size of the body of the response.
  • Set-Cookie: Sends cookies from the server to the client.
• Response Body: If the response includes a body, it contains the resource or information requested. This can be in formats like HTML, JSON, XML, etc.

Example

Let's see the response for the GET request we made earlier.

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
  "body": "quia et suscipit\\nsuscipit..."
}

Breakdown

• Status Line: HTTP/1.1 200 OK
• Response Headers:
  • Content-Type: application/json; charset=utf-8
  • Content-Length: 292
• Response Body: JSON data with details about the post.

Additional Concepts

• Cookies: Small pieces of data sent from the server and stored on the client, used for session management, tracking, and personalization.
• Caching: Mechanisms to store copies of web resources to reduce latency and server load. Headers like Cache-Control and Expires control caching behavior.
• Security: HTTPS is used to encrypt web requests and responses, ensuring data integrity and confidentiality. Headers like Strict-Transport-Security enforce the use of HTTPS.

Understanding these components and how they interact is essential for diagnosing issues, optimizing performance, and securing web applications.