gulp task `open`

gulpfile.js

var SERVER_PORT = 5000;

// Opens browser window using internal IP on the assigned SERVER_PORT
gulp.task('open', function() {
  var os = require('os');
  var spawn = require('child_process').spawn

  var interfaces = os.networkInterfaces();
  var addresses = [];
  for (k in interfaces) {
      for (k2 in interfaces[k]) {
          var address = interfaces[k][k2];
          if (address.family == 'IPv4' && !address.internal) {
              addresses.push(address.address)
          }
      }
  }
  var openAddress = addresses[0] || 'localhost';

  spawn('open', ['http://'+ openAddress + ':' + SERVER_PORT]);
});