Example node

/* To run:
Install node 10 or 12
  npm init
(Follow prompts - you can just press enter all the way through it).
  npm install --save express
  npm install --save child_process
  node index.js (or what ever you called your file)

In Chrome/Firefox navigate to:
  127.0.0.1:3000/your/path/to/page
You should see it return the contents of your home directory
// */

const { exec } = require('child_process');
const express = require('express');

const app = express();
const port = process.env.PORT || 3000;
const ip = process.env.IP || '0.0.0.0'; // You can just put a single interface here, such as 192.168.1.2, 0.0.0.0 listens to all

const allowedIpAddresses = [
  "192.168.1.", // Does partial matching.
  "127.0.0.1"
];

// Util functions
const getRemoteIp = (req) => {
  return req.connection.remoteAddress || req.socket.remoteAddress || req.headers['x-forwarded-for'];
};

const ipAllowed = (remoteIp, ipList) => {
  for (let i = 0; i < ipList.length; i++) {
    if (ipList[i].indexOf(remoteIp) > -1) {
      return true;
    }
  }

  return false;
};

// Some logic
const exampleFunction = (req, res) => {
  res.send('Example!');
};

// Route hooks
app.get('/your/path/to/page', (req, res) => {
  // Execute system command.
  // Note that it has the same privledges as the user that ran Node. You cannot use sudo here unless you started node with sudo
  // And please do not start node with sudo. Very easy for hackers to take over your system.
  // Please PLEASE _PLEASE_ learn how to secure your system. Yuri commands it.
  exec('ls ~', (err, stdout, stderr) => {
    if (err) {
      res.status(500);
      res.send({
        error: 'Failed to execute command',
        reason: err,
        stdout,
        stderr
      });
      return;
    }

    res.status(200);
    res.send({
      error: 'Command executed',
      stdout,
      stderr
    });
  });
});

app.get('/another/path/to/page', (req, res) => {
  exampleFunction(req, res)
});

app.get('/ip/check', (req, res) => {
  const remoteIp = getRemoteIp(req);

  if (ipAllowed(remoteIp, allowedIpAddresses)) {
    res.status(200);
    res.send('Good boi');
    return;
  }
  res.status(401);
  res.send('Bad boi');
  return;
});

app.all('/', (req, res) => {
  res.send('Uhh, hi');
});

app.listen(port, ip, function () {
  console.log(`My command is your wish ${ip}:${port}!`);
});