Web and HTTP Basics

Web and HTTP

• The World Wide Web (WWW) is a vast network of interconnected documents and resources.
• It's linked by hyperlinks and URLs.
• Users access information and services over the internet using web browsers.
• The web plays a crucial role in data management, communication, and automation.

Client-Server Model

• The web operates on a client-server model.
• A client (typically a web browser) requests resources from a server.
• The server then sends the requested data back to the client.
• The client is the end-user device (like a desktop, smartphone, etc.) running a web browser, and it sends HTTP/HTTPS requests for web resources.
• The server is a powerful machine hosting websites and resources, providing them to clients.
• Servers handle multiple requests simultaneously using various technologies (e.g., Apache, IIS).

Components of the Web

• Web Browsers: Software applications (like Chrome, Firefox, Safari) allowing users to access and navigate the web.
• Web Servers: Computers storing, processing and serving webpages to clients (browsers), upon request; Examples include Apache and IIS.
• Web Pages: Documents formatted in HTML (HyperText Markup Language) containing text, images, and links.
• URLs: Uniform Resource Locators - addresses used to locate resources on the web. A URL specifies the protocol (HTTP or HTTPS), the domain name, and the path to the resource.

What is HTTP?

• HTTP (HyperText Transfer Protocol) is the foundation for transmitting data over the web.
• It defines how web messages are formatted and transmitted, and how servers and browsers respond to commands.

Key Features of HTTP

• Stateless Protocol: Each request from a client to a server is treated as an independent transaction. The server doesn't retain information about previous requests.
• Request-Response Model: Communication involves a client sending a request to a server. The server responds with the requested resource or an error message.

HTTP Methods

• GET: Requests data from a specified resource.
• POST: Submits data to be processed by a specified resource.
• PUT: Updates a specified resource with new data.
• DELETE: Removes a specified resource.

HTTP Status Codes

• 200 OK: The request was successful.
• 404 Not Found: The requested resource could not be found.
• 500 Internal Server Error: The server encountered an unexpected condition.

How to See Status Codes (Google Chrome)

• Open Google Chrome and navigate to the website.
• Right-click anywhere on the page and select Inspect.
• Or press Ctrl + Shift + I (Windows/Linux) or Cmd + Option + I (Mac)
• Go to the Network tab.
• Refresh the page (press F5 or click refresh icon).
• Look for status codes in the Status column.

1xx: Informational

• 100 Continue: Initial part of a request has been received, and client can continue.
• 101 Switching Protocols: Server is switching protocols as requested by the client.

2xx: Success

• 200 OK: Request was successful.
• 201 Created: Request fulfilled, and a new resource created.
• 204 No Content: Request was successful, but there's no content to send.

3xx: Redirection

• 301 Moved Permanently: Requested resource moved to a new URL.
• 302 Found: Requested resource temporarily located at a different URL.
• 304 Not Modified: Resource hasn't changed since last request.

4xx: Client Errors

• 400 Bad Request: Request couldn't be understood or missing required parameters.
• 401 Unauthorized: Authentication required but failed or not provided.
• 404 Not Found: Requested resource can't be found.

5xx: Server Errors

• 500 Internal Server Error: Generic error, server encountered an unexpected condition.
• 502 Bad Gateway: Server acted as a gateway and received an invalid response.
• 503 Service Unavailable: Server can't handle request due to overload or maintenance.

Headers

• HTTP headers provide essential information about the request or response. Examples include content type, length, and encoding.

HTTPS

• HTTPS (HyperText Transfer Protocol Secure) is an extension of HTTP with security features.
• It uses SSL/TLS to encrypt data transmitted between client and server.
• This is important for transactions involving sensitive information.

Web Technologies

• HTML: Standard markup language for creating webpages. HTML structures content on the web.
• CSS: Style sheet language defining presentation (layout, colors, fonts) of HTML documents.
• JavaScript: Programming language for creating dynamic, interactive web content; updates happen without reloading the page.

Cookies & Sessions

• Cookies: Small pieces of data sent from a server to a client, often used for storing user preferences and session information.
• Sessions: Maintain user state across multiple requests. Mechanisms like cookies are often used for this.

Importance of Web in Industrial Engineering

• Data Access: Engineers access and use online data for research & development.
• Collaboration: Real-time collaboration tools enhance efficiency across large teams.
• Automation: Web interfaces monitor and control industrial processes more efficiently.
• E-Commerce: Web technologies help businesses with online sales, supply chain management, and customer relations.