Start nodejs server on centos
The server.js file has indeed been removed from the package. The solution is in the readme:


  Setup
  
  
  Install drupal-node.js packge with npm:
  
  npm install drupal-node.js
  
  
  Make sure to do this outside of your Drupal modules directory, else
  Drupal may try to process folders containing Node.js module
  information and fail. Follow the install instructions in the
  drupal-node.js NPM package. You will need to provide the hostname and
  port of your Drupal site to the Node.js process, and ensure that the
  service token matches between Drupal and Node.js.


I suppose they separated the server from the Drupal module to allow more frequent updates.
The npm package contains a settings file and app.js, which includes server.js.