Initial deploy bundle for WebRTC signaling server and multipeer demo.

Co-authored-by: Cursor <cursoragent@cursor.com>

server.js

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+/***
+ * Excerpted from "Programming WebRTC",
+ * published by The Pragmatic Bookshelf.
+ * Copyrights apply to this code. It may not be used to create training material,
+ * courses, books, articles, and the like. Contact us if you are in doubt.
+ * We make no guarantees that this code is fit for any purpose.
+ * Visit https://pragprog.com/titles/ksrtc for more book information.
+***/
+'use strict';
+
+// Load up necessary modules
+const crypto = require('crypto');
+
+// snip, snip...
+
+const createError = require('http-errors');
+const express = require('express');
+const path = require('path');
+const logger = require('morgan');
+const io = require('socket.io')();
+// Create an Express app
+const app = express();
+// Set the public directory to serve from
+const public_dir = process.env.PUBLIC ?? 'www';
+// Log activity to the console
+app.use(logger('dev'));
+// Serve static files from the `www/` directory
+app.use(express.static(path.join(__dirname, public_dir)));
+
+// Catch 404 errors and forward them to error handler
+app.use(function(req, res, next) {
+  next(createError(404));
+});
+// Handle errors with the error handler
+app.use(function(err, req, res, next) {
+  // Set the error code
+  res.status(err.status || 500);
+  // Respond with a static error page (404 or 500)
+  res.sendFile(`error/${err.status}.html`, { root: __dirname });
+});
+
+/**
+ *  The main monkey business:
+ *  Signaling with the socket server, Socket.io
+ */
+
+const mp_namespaces = io.of(/^\/[a-z]{4}\-[a-z]{4}\-[a-z]{4}$/);
+
+mp_namespaces.on('connect', function(socket) {
+
+  const namespace = socket.nsp;
+
+  const expiry_in_hours = 4; // credentials last for four hours
+  const secret = process.env.TURNSECRET || 'your secret goes here';
+  const credentials = createCoturnCredentials(expiry_in_hours, secret);
+
+  const peers = [];
+
+  for (let peer of namespace.sockets.keys()) {
+    peers.push(peer);
+  }
+  console.log(`    Socket namespace: ${namespace.name}`);
+
+  // Send the array of connected-peer IDs and the TURN credentials
+  // to the connecting peer
+  socket.emit('connected peers', { peers, credentials });
+
+  // Send the connecting peer ID to all connected peers
+  socket.broadcast.emit('connected peer', socket.id);
+
+  socket.on('signal', function({ recipient, sender, signal }) {
+    socket.to(recipient).emit('signal', { recipient, sender, signal });
+  });
+
+  socket.on('disconnect', function() {
+    namespace.emit('disconnected peer', socket.id);
+  });
+
+});
+
+/**
+ *  End of the main monkey business.
+ */
+
+function createCoturnCredentials(expiry_in_hours, secret) {
+  // JavaScript timestamps are in milliseconds, so divide by 1000
+  const now = Math.round(Date.now() / 1000);
+  const expiry = (now + (expiry_in_hours * 60 * 60)).toString();
+  const hmac = crypto.createHmac('sha1', secret);
+  hmac.setEncoding('base64');
+  hmac.write(expiry);
+  hmac.end();
+  return {
+    username: expiry,
+    password: hmac.read()
+  };
+}
+
+// Export the Express app and Socket.io instances for use in
+// /scripts/start-server:
+module.exports = {app, io, public_dir};