Gulp to watch when node app.listen() is invoked or to port (livereload, nodejs and gulp)

Question

I am trying to get gulp-livereload to work with my nodejs server. I am using gulp-nodemon to restart the server after changes to the files, this works. I am having trouble invoking livereload.reload() at the correct time.

I am currently invoking livereload.reload() on the .on('start'... in my gulpfile.js (whenever my nodemon starts a script). This works but it takes a few seconds. The reason is when nodemon starts to run the nodejs script it invokes livereload.listen() before the script has invoked app.listen(port), so my browser refreshs without the server being ready.

Is there a way to listen if the nodejs nodemon script has invoked app.listen(port) or perhaps listen to see if a specific port is being used?

I have fixed the issue with a small sleep but it just feels so wrong and dirty.

Answer 1

Use readable event to monitor stdout of child process.

example:

nodemon({script: 'app.js',
         nodeArgs: ['--harmony'],
         stdout: false})
    .on('readable', function(data) {
        this.stdout.on('data', function(chunk) {
            if (/koa server listening/.test(chunk)) {
                console.log('livereload');
                livereload.reload();
            }
            process.stdout.write(chunk);
        });
        this.stderr.pipe(process.stderr);
    });

app.js

app.listen(3000, function(err) {
    console.log('koa server listening');
});

Answer 2

Here is a an example of simple and tested livereload solution based on connect server and connect-livereload and gulp-livereload plugins if that is of any help:

var gulp = require('gulp');
var connect = require('connect');
var connectLivereload = require('connect-livereload');
var opn = require('opn');
var gulpLivereload = require('gulp-livereload');

var config = {
    rootDir: __dirname,
    servingPort: 8080,

    // the files you want to watch for changes for live reload
    filesToWatch: ['*.{html,css,js}', '!Gulpfile.js']
}

// The default task - called when you run `gulp` from CLI
gulp.task('default', ['watch', 'serve']);

gulp.task('watch', ['connect'], function () {
  gulpLivereload.listen();
  gulp.watch(config.filesToWatch, function(file) {
    gulp.src(file.path)
      .pipe(gulpLivereload());
  });
});

gulp.task('serve', ['connect'], function () {
  return opn('http://localhost:' + config.servingPort);
});

gulp.task('connect', function(){
  return connect()
    .use(connectLivereload())
    .use(connect.static(config.rootDir))
    .listen(config.servingPort);
});