server.js

var express = require('express');
var httpProxy = require('http-proxy');

var app = express();
var proxy = httpProxy.createProxyServer();

var port = isProduction ? process.env.PORT : 3000;
var isProduction = process.env.NODE_ENV === 'production';

app.use(express.static('public'));
app.use('/assets', express.static('assets'));

// We only want to run the workflow when not in production
if (!isProduction) {

  // We require the bundler inside the if block because
  // it is only needed in a development environment. Later
  // you will see why this is a good idea
  var bundle = require('./server/bundle.js');
  bundle();

  // Any requests to localhost:3000/build is proxied
  // to webpack-dev-server
  app.all('/build/*', function (req, res) {
    proxy.web(req, res, {
        target: 'http://localhost:8080'
    });
  });

}

proxy.on('error', function(e) {
  console.log('Could not connect to proxy, please try again...');
});

app.listen(port, function () {
  console.log('Server running on port ' + port);
});