Introduction to the Internet and Web Technologies

The Internet

• The Internet is a global network connecting billions of devices that use HTTP (Hypertext Transfer Protocol) to communicate.
• HTML (Hypertext Markup Language) allows different devices to understand each other.
• The first web browser and web server were created to connect devices together.

Web Browsers

• Web browsers are programs that retrieve and display documents from web servers.
• Popular web browsers include Mozilla Firefox, Microsoft Internet Explorer, Apple Safari, Google Chrome and Opera.

HTTP

• HTTP is a set of commands understood by web servers and sent from web browsers.
• Common HTTP commands include:
  • GET filename: Downloads a file.
  • POST filename: Sends a web form response, which creates a new resource.
  • PUT filename: Uploads a file, which updates an existing resource.

URLs

• URLs (Uniform Resource Locators) identify the location of a document on a website.
• When a browser uses a URL, it:
  • Asks the DNS server for the IP address of the website.
  • Connects to that IP address at port 80.
  • Asks the server to GET the specified file.
  • Displays the resulting page on the user's screen.

Servers

• A server is a computer or device on a network that manages network resources.
• Different types of servers include:
  • File servers: Store files for network users to access.
  • Print servers: Manage printers for the network.
  • Network servers: Manage and regulate network traffic.
  • Database servers: Process database queries.

Web Servers

• A web server is a computer or application that delivers web content accessible through the internet.
• Webservers process user requests via HTTP.
• They store, process, and deliver webpages to the client.
• A web server receives requests from the client, generates a response, and sends it back to the client.

Client-Side vs. Server-Side

• Client-Side: The user's browser (e.g., Chrome, Safari) interacts with a server to perform actions. This focuses on the user interface and displaying data.
• Server-Side: The systems behind the scenes that manage data and logic. This includes storing and processing information.

Types of Web Servers

• Apache HTTP Server: One of the most popular web servers in the world. It's open-source, runs on various operating systems, and can be adapted for specific needs. Popular sites using Apache include Youtube, Wikipedia, Ask.com, and Apple.com.
• Internet Information Services (IIS): Developed by Microsoft, IIS is a flexible, secure, and manageable webserver for hosting diverse content on the web. It is integrated with Windows operating systems and easy to administer.
• Nginx: Nginx is a high-performance web server used as a reverse proxy, load balancer, mail proxy, and HTTP cache. It is open-source and serves over 146 million websites, including Netflix, Dropbox, Pinterest, WordPress.com, Instagram, GitHub, and SoundCloud.

Static Web Pages

• Static web pages deliver the same fixed content to every user without any dynamic generation or processing. This makes them efficient to transmit over the internet.
• The content is stored as a file, and the server sends the same file to each user, making these pages fast and easy for websites to deliver.

Dynamic Content

• Dynamic content changes based on the user's preferences, behavior, and interests.
• The same document can return different results based on who is making the request.
• Web servers need to run programs like PHP, ASP, etc., to process requests and generate dynamic content.

Web Development

• Dynamic websites consist of two main parts:
  • Front-end: The visible part of the website that users interact with through their web browsers.
  • Back-end: Controls the website's functionality, including data storage and processing. It's behind the scenes and not directly visible to the user.