static-file-server.js

const fs = require('fs')
const http = require('http')
const path = require('path')

const server = http.createServer((req, res) => {
  // `req` is the request object; `res` is the response

  // Use the requested URL to serve a file in the `files` directory
  const readStream = fs.createReadStream(path.join('files', req.url))
  readStream.on('error', _ => {
    // Tell the client if the file didn't exist
    res.write('File not found')
    res.end()
  })
  // `res` is a writable stream. Piping the file to it sends it to the client.
  readStream.pipe(res)
})
// Listen for requests on port 80 (the default for HTTP)
server.listen(80)