Basic gulpfile.js for serve static files for gulp version 4+

gulpfile.js

// Add our dependencies
var gulp = require('gulp'), // Main Gulp module
    concat = require('gulp-concat'), // Gulp File concatenation plugin
    open = require('gulp-open'), // Gulp browser opening plugin
    connect = require('gulp-connect'); // Gulp Web server runner plugin

// Configuration
var configuration = {
    paths: {
        src: {
            html: './src/*.html',
            css: [
                './src/css/bootstrap.min.css',
                './src/css/main.css'
            ]
        },
        dist: './dist'
    },
    localServer: {
        port: 8001,
        url: 'http://localhost:8001/'
    }
};

// Gulp task to copy HTML files to output directory
gulp.task('html', function() {
    gulp.src(configuration.paths.src.html)
        .pipe(gulp.dest(configuration.paths.dist))
        .pipe(connect.reload());
});

// Gulp task to concatenate our css files
gulp.task('css', function () {
   gulp.src(configuration.paths.src.css)
       .pipe(concat('site.css'))
       .pipe(gulp.dest(configuration.paths.dist + '/css'))
       .pipe(connect.reload());
});

// Gulp task to create a web server
gulp.task('connect', function () {
    connect.server({
        root: 'dist',
        port: configuration.localServer.port,
        livereload: true
    });
});

// Gulp task to open the default web browser
gulp.task('open', function(){
    gulp.src('dist/index.html')
        .pipe(open({uri: configuration.localServer.url}));
});

// Watch the file system and reload the website automatically
gulp.task('watch', function () {
    gulp.watch(configuration.paths.src.html, ['html']);
    gulp.watch(configuration.paths.src.css, ['css']);
});

// Gulp default task
gulp.task('default', gulp.series('html', 'css', 'connect', 'open', 'watch'));