javascript - browser livereload not working when using grunt-contrib-watch with combination of grunt-express -

i started test livereload ability of combination of grunt watch plugin (grunbt-contrib-watch) , grunt express server (grunt-express). directory has gruntfile.js file in root directory, npm modules installed in npm_modules folder , there folder called "build" contains 1 html file. 3 packages installed using npm :

1. grunt
2. grunt-contrib-watch
3. grunt-express

they working fine. watch plugin watching html file , server running @ localhost:3000, problem livereload property of express plugin not working when change html file. can't figure out why?

my guntfile.js looks bellow:

module.exports = function(grunt) { grunt.initconfig({     watch: {         html: {             files: ['build/*.html'],             tasks: []         }     },     express: {         all: {             options: {                 bases: 'build',                 livereload: true,                 open: 'http://localhost:3000'             }         }     } }); grunt.loadnpmtasks('grunt-contrib-watch'); grunt.loadnpmtasks('grunt-express'); grunt.registertask('start', ['express','watch']); 

};

on watch config add:

 options: {           nospawn: true,           atbegin: true,         } 

ref link: http://thanpol.as/grunt/grunt-with-express-server-and-livereload/