index.js

const express = require('express');
const app = express();
const fs = require('fs');

app.get('/', function (req, res) {
  res.sendFile(__dirname + '/index.html');
});

app.get('/video', function (req, res) {
  const range = req.headers.range;
  if (!range) {
    res.status(400).send('Requires Range header');
  }

  const videoPath = 'piper.mkv';
  const videoSize = fs.statSync('piper.mkv').size;

  const CHUNK_SIZE = 10 ** 6; // 1MB
  const start = Number(range.replace(/\D/g, ''));
  const end = Math.min(start + CHUNK_SIZE, videoSize - 1);

  const contentLength = end - start + 1;
  const headers = {
    'Content-Range': `bytes ${start}-${end}/${videoSize}`,
    'Accept-Ranges': 'bytes',
    'Content-Length': contentLength,
    'Content-Type': 'video/mp4',
  };

  // HTTP Status 206 for Partial Content
  res.writeHead(206, headers);

  // create video read stream for this particular chunk
  const videoStream = fs.createReadStream(videoPath, { start, end });

  // Stream the video chunk to the client
  videoStream.pipe(res);
});

app.listen(3000, function () {
  console.log('Listening on port 3000!');
});