excalidraw_room_0/src/index.ts

import express from "express";
import http, { ServerResponse } from "http";
import socketIO from "socket.io";

const app = express();
const port = process.env.PORT || 80; // default port to listen

const server = http.createServer(app);

server.listen(port, () => {
  console.log(`listening on port: ${port}`);
});

const io = socketIO(server, {
  handlePreflightRequest: function(req, res) {
    var headers = {
      "Access-Control-Allow-Headers": "Content-Type, Authorization",
      "Access-Control-Allow-Origin": req.header ? req.header.origin : "*",
      "Access-Control-Allow-Credentials": true
    };
    res.writeHead(200, headers);
    res.end();
  }
});

io.on("connection", socket => {
  console.log("connection established!");
  io.to(`${socket.id}`).emit("init-room");
  socket.on("join-room", roomID => {
    console.log(`${socket.id} has joined ${roomID}`);
    socket.join(roomID);
    if (io.sockets.adapter.rooms[roomID].length <= 1) {
      io.to(`${socket.id}`).emit("first-in-room");
    } else {
      socket.broadcast.to(roomID).emit("new-user", socket.id);
    }
    io.in(roomID).emit(
      "room-user-count",
      io.sockets.adapter.rooms[roomID].length
    );
  });

  socket.on("server-broadcast", (roomID: string, encryptedData: ArrayBuffer, iv: Uint8Array) => {
    console.log(`${socket.id} sends update to ${roomID}`);
    socket.broadcast.to(roomID).emit("client-broadcast", encryptedData, iv);
  });

  socket.on("disconnecting", () => {
    const rooms = io.sockets.adapter.rooms;
    for (const roomID in socket.rooms) {
      const remaining = rooms[roomID].length - 1;
      if (remaining > 0) {
        socket.broadcast.to(roomID).emit("room-user-count", remaining);
      }
    }
  });

  socket.on("disconnect", () => {
    socket.removeAllListeners();
  });
});