Flow.js Node Server renames the uploaded file but cannot emit the changed file name to the Javascript client.

app.js

process.env.TMPDIR = 'tmp'; // to avoid the EXDEV rename error, see http://stackoverflow.com/q/21071303/76173
var UPLOAD_DIR = 'uploads/';

var express = require('express');
var multipart = require('connect-multiparty');
var multipartMiddleware = multipart();
var flow = require('./flow-node.js')('tmp');
var fs = require('fs');
var crypto = require('crypto');
var path = require('path');
var app = express();

// Configure access control allow origin header stuff
var ACCESS_CONTROLL_ALLOW_ORIGIN = false;

// Host most stuff in the public folder
app.use(express.static(__dirname + '/../prototype'));
app.use(express.static(__dirname + '/uploads'));

var getHashFromFile = function(filepath, filename, callback) {
  var completePath = filepath + filename;
  // Read the file again and create a hash for it
  var shasum = crypto.createHash('sha256');
  var reader = fs.ReadStream(completePath);
  reader.on('data', function(hash) {
    shasum.update(hash);
  });

  reader.on('end', function() {
    var hash = shasum.digest('hex');
    callback(hash);
  });
}

app.post('/upload', multipartMiddleware, function(req, res) {
  flow.post(req, function(status, filename, original_filename, identifier) {
    if (status == 'done') {
      var filepath = UPLOAD_DIR + filename;
      var stream = fs.createWriteStream(filepath);
      console.log(identifier);
      flow.write(identifier, stream);
      flow.clean(identifier);

      // Here I calculate a hash based on the uploaded file and rename it accordingly.
      getHashFromFile(UPLOAD_DIR, filename, function(hash){
        var extension = path.extname(filename);
        fs.rename(UPLOAD_DIR + filename, UPLOAD_DIR + hash + extension, function(err) {
          if ( err ) console.log('ERROR: ' + err);
        });
      });
    }
    if (ACCESS_CONTROLL_ALLOW_ORIGIN) {
      res.header("Access-Control-Allow-Origin", "*");
    }
    res.status(status).send();
  });
});


app.options('/upload', function(req, res){
  console.log('OPTIONS');
  if (ACCESS_CONTROLL_ALLOW_ORIGIN) {
    res.header("Access-Control-Allow-Origin", "*");
  }
  res.status(200).send();
});

// Handle status checks on chunks through Flow.js
app.get('/upload', function(req, res) {
  flow.get(req, function(status, filename, original_filename, identifier) {
    console.log('GET', status);
    console.log('GET', filename);
    console.log('GET', original_filename);
    if (ACCESS_CONTROLL_ALLOW_ORIGIN) {
      res.header("Access-Control-Allow-Origin", "*");
    }

    if (status == 'found') {
      status = 200;
    } else {
      status = 404;
    }
    res.status(status).send();
  });
});

app.get('/download/:identifier', function(req, res) {
  flow.write(req.params.identifier, res);
});

var port = 8888;
console.log("Started listening on Port " + port);
app.listen(port);