WWW (INFO30005 W1)

How was the www invented?

• 1990
• Tim Berners-Lee and Nicola Pellow built the first web browser

How does it work?

• In 90s:
• Hypertext (navigation through hypercards) as HTML, internet as HTTP: WWW (1990)
• WWW = HTML + HTTP + URL
  • WWW: Extend the idea of hypertext on one computer to hypertext over any computer
  • HTML defines the structure of the document, and how the links work
  • HTTP defines how the messages run between the computers

What is a web app?

• The web is not the internet; it’s an application that runs on the internet
• Internet itself is another set of protocols
• Once you have the TCP/IP layers, you have the ability to build applications at a higher level and invent a protocol that involves messages being sent back and forth.

HTTP

• v 0.9 (1991) one verb: GET a resource
• HTML2 (1995) <FORM> tag ○ No longer a read-only web (login names & pw, description of order, etc.)
• v 1.0 (1996) GET and POST messages
• v 1.1 (1997) GET POST PUT DELETE a resource
• (2010) PATCH (partially) update a resource

WWW is client-server

• Client sends GET/POST/PUT/DELETE request, then the executes the corresponding script. (output is HTML or JSON)
• Most of the times DB is involved.

Running a server using Node.js

const http = require('http')
// Create a server ready to take action
// Callback function runs everytime server recieves an http request
const server = http.createServer( (req, res) => {
  console.log('someone connected to the server')

  // Add stuff to the browser (make a little web page!)
  res.write('<h1>Hello, world!</h1>')
  res.write('<p>Hello again</p>')
  res.end()
})

// Listen to the server at the particular TCP/IP port
server.listen(8080, () => {
  console.log('listening on 8080')
})

What is a server?

• a computer running server software (e.g. Apache, MS IIS, Node.js)
• ‘listens’ on a particular TCP/IP port
• accepts Requests, sends Responses
• runs application code to make responses
• your dev laptop is a server (localhost)
• can be ‘on premise’ or ‘in the cloud’
• trend is to host web apps on cloud platforms (e.g. Heroku, Firebase, AWS, Azure)
• ‘serverless’ auto-scaling
• microservice architectures

What does a web developer do?

• design the user interface (a set of HTML files, CSS stylesheets, and other assets)
• set up and program a web server such that it delivers these assets when requested by authorised users