app.js

var express = require('express');
var app = express();
var http = require('http').Server(app);
var io = require('socket.io').listen(http);
var SocketIOFile = require('socket.io-file');
var chatEncrypted = false;
var userCount = 0;
var sleep = require('system-sleep');

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

app.use(express.static(__dirname + '/public'));

app.get('/socket.io-file-client.js', (req, res, next) => {
  return res.sendFile(__dirname + '/node_modules/socket.io-file-client/socket.io-file-client.js');
});

app.get('/download/:path', function(req, res) {
  var file = __dirname + '/data/' + req.params.path;
  res.download(file); // Set disposition and send it.
});

http.listen(3000, "0.0.0.0", function() {
  console.log('listening on *:3000');
});

io.on('connection', function(socket) {
  userCount += 1;
  if (userCount == 2) {
    sleep(1000); // sleep for 10 seconds
    io.emit('startRSA');

  }

  var uploader = new SocketIOFile(socket, {
    uploadDir: 'data',
    chunkSize: 10240,
    transmissionDelay: 0,
    overwrite: true
  });

  uploader.on('start', (fileInfo) => {
    console.log('Start uploading');
    console.log(fileInfo);
  });
  uploader.on('stream', (fileInfo) => {
    console.log(`${fileInfo.wrote} / ${fileInfo.size} byte(s)`);
  });
  uploader.on('complete', (fileInfo) => {
    console.log('Upload Complete.');
    console.log(fileInfo.name);
    io.emit('file', fileInfo.data + '$' + fileInfo.name);
  });
  uploader.on('error', (err) => {
    console.log('Error!', err);
  });
  uploader.on('abort', (fileInfo) => {
    console.log('Aborted: ', fileInfo);
  });

  // send normal message to everyone
  socket.on('normalMessage', function(msg) {
    io.emit('normalMessage', msg);
  });

  // send encrypted message to everyone
  socket.on('encryptedMessage', function(msg) {
    if (chatEncrypted) {
      io.emit('encryptedMessage', msg);
    } else {
      console.log("Chat not encrypted yet");
    }
  });

  // User started the encrypt protocol
  socket.on('encryptProtocol', function(msg) {
    console.log("Encryption protocol started");
    socket.broadcast.emit('encryptedMessage');
    socket.broadcast.emit('step1'); // Start step 1
    chatEncrypted = true; // when we have a sucessful encrypted pipe
  });

  // swap RSA public keys
  socket.on('sendPublicKey', function(msg) {
    socket.broadcast.emit('receivePublicKey', msg);
  });

  // Step 2
  socket.on('getResponseStep2', function(msg) {
    socket.broadcast.emit('step2', msg);
  });

  // Step 3
  socket.on('getResponseStep3', function(msg) {
    socket.broadcast.emit('step3', msg);
  });

  // Step 4
  socket.on('getResponseStep4', function(msg) {
    socket.broadcast.emit('step4', msg);
  });

  // User uploads a file
  socket.on('file', function(msg) {
    console.log("file uploaded")
    io.emit('file', 'File Uploaded');
  });

  // Step 4
  socket.on('encryptionSuccessful', function(msg) {
    socket.emit('sendEncryptedMessage', msg);
  });

  socket.on('disconnect', function() {
    //console.log('user disconnected');
    userCount += -1;
  });
});