What to define as 'host' when deploying my node gulp app to heroku?

I am trying to push my gulp node app to heroku. In the package.json I have "postinstall": "gulp serveprod" to run a gulp command that starts a webserver.

In package.json

"scripts": {
    "start": "node app",
    "postinstall": "gulp serveprod",
    ...etc
}

My gulp task:

gulp.task('serveprod', function() {
  connect.server({
    root: 'app',
    host: '',
    port: process.env.PORT,
    livereload: false,
    open: false
  });
});

When I run 'gulp serveprod' in the terminal the app works fine on localhost. However when I run 'gulp push heroku" I get the following that stays until it timesout:

  postinstall /tmp/build_c27e9c799bef2671ed033b271feecf87
remote:        > gulp serveprod
remote:        
remote:        [03:54:36] Using gulpfile /tmp/build_c27e9c799bef2671ed033b271feecf87/gulpfile.js
remote:        [03:54:36] Starting 'serveprod'...
remote:        [03:54:36] Finished 'serveprod' after 12 ms
remote:        [03:54:36] Server started http://localhost:8080

My understanding is that the gulp server is using localhost by default and I need to specify the host where heroku will host the app. However I have no idea what to put as 'host'.

I looked at this answer and tried '0.0.0.0' which didn't work. I have also tried http://infinite-lowlands-6023.herokuapp.com/ which is the name of my app which got a similar result, pushing to heroku would just stop at this gulp task. I have followed this question that helped me get through other issues but I am now well and truly stuck on this one.

What do I need to do to deploy this to Heroku successfully? What information needs to go in the 'host' value?

Thanks :)