gulp 4

gulp-webserver
$ npm i -D gulp-webserver

var gulp = require('gulp');
var imagemin = require('gulp-imagemin');
var coffee = require('gulp-coffee');
var concat = require('gulp-concat');
var uglify = require('gulp-uglify');
var plumber = require('gulp-plumber');
var header = require('gulp-header');
var webserver = require('gulp-webserver');

gulp.task('html', function(done){
	gulp.src('./src/index.html')
		.pipe(gulp.dest('./dest'))
	done();
});

gulp.task('img', function(done){
	gulp.src('./src/img/*.png')
		.pipe(imagemin())
		.pipe(gulp.dest('./dest/img'))
	done();
});

gulp.task('js', function(done){
	gulp.src('./src/coffee/*.coffee')
		.pipe(plumber())
		.pipe(coffee())
		.pipe(concat('all.min.js'))
		.pipe(uglify())
		.pipe(header('/* copry righ @hpscript */'))
		.pipe(gulp.dest('./dest/js'))
	done();
});

gulp.task('watch', function(done){
	gulp.watch('./src/coffee/*.coffee', gulp.task('js'))
	gulp.watch('./src/*.html', gulp.task('html'))
	done();
});

gulp.task('webserver', function(done){
	gulp.src('./dist')
		.pipe(webserver({
			host:'192.168.34.10',
			livereload: true
		}));
	done();
});

gulp.task('default', gulp.series('html','img','js','watch','webserver'));

きた。livereloadが動かないと思ったら、htmlタグでないとダメのようね。
OK。では、sass + gulpの環境を考えましょう