Create a simple Express.js server to shutdown your PC remotely.🤖

#javascript #node #programming #systems

The inspiration

I am a very lazy person. I sometimes go to take a nap & because I'm already in bed, I do not want to stand up & go shutdown my PC myself.

So that's why I thought to myself I might create some small script that listens to a certain port & runs as a daemon/service in the background. That should save me standing up from my bed.

Choosing how to implement the idea

At first I thought I should make some sockets, given the simplicity of the task, but because this is too low-level for me & as I mentioned before I am too lazy to do everything by hand, I eventually chose Express.JS. Given that it is easy to setup a simple HTTP server very quickly & easily.

Actual implementation

For the actual implementation.

I started out by creating a Node.js program with:

npm init

Then I installed my dependencies:

npm i express

The programming began with setting up a GET method that fires a windows command. To fire command line commands within Node.js use the child_process module.

We implement the auxiliary shutdown function, that executes the shutdown signal, here I added the time flag -t & gave it 30 seconds so the shutdown takes 30 seconds. Feel free to add whatever options you want, maybe even a restart.

Useful tip use shutdown -a to cancel the programmed shutdown or restart.

const exec = require('child_process').exec;
// Create shutdown function
function shutdown(callback) {
  exec('shutdown -s -t 0030', 
      function (error, stdout, stderr) { callback(stdout); });
}

Here is the first GET method:

app.get('/', (req, res) => {
  res.sendFile(path.join(__dirname, 'public/home.html'))
});

As you can see I decided to serve an HTML page statically.
This page has a stylized shut-down button. When clicked, the button fires the actual shutdown command and another GET request that shows a countdown till shutdown.

app.get('/shutdown', (req, res) => {
  res.sendFile(path.join(__dirname, 'public/shutting-down.html'))
  // shutdown computer
  shutdown(function (output) {
    console.log('received shutdown command');
  });
})

Serving the static files

Now that the functionality is implemented, you can opt to using a template engine like Pug, but I stuck with simple way of serving static files.
For that you need to use the static middleware from Express.js.
I created a public directory where the static files will be & used the middleware to point to it.

app.use(express.static("public"));

Styling

I used following snippets for my button styling and the counter. I also used font-awesome's CDN, to get the power-off icon.

CSS Counter
Really well written code you only need to change the duration to your liking and embed it in your served HTML.

CSS Pulse power-off
You just need to change the color and add the desired icon from font-awesome.

Creating the service

Under Linux this is no issue using systemctl.
With Windows it is kinda tricky you need to first download and install nssm. For brevity I won't explain how to install it. But it should be very simple. And it'll help you a lot.
Now that we have nssm installed we now need to convert our index.js to an index.exe. To do that we need to install the pkg dependency globally.