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public/client.js

 const faye = new Faye.Client('/faye', { timeout: 120 });
+
+// get data from socket end set UI text
 faye.subscribe('/drone/navdata', data => {
   [
     'batteryPercentage',
@@ -12,7 +14,6 @@ faye.subscribe('/drone/navdata', data => {
   ].forEach(type => $('#' + type).html(Math.round(data.demo[type], 4)));
   return showBatteryStatus(data.demo.batteryPercentage);
 });
-
 window.showBatteryStatus = batteryPercentage => {
   $('#batterybar').width(`${batteryPercentage}%`);
   if (batteryPercentage < 30)
@@ -27,9 +28,12 @@ window.showBatteryStatus = batteryPercentage => {
     'data-original-title': `Battery status: ${batteryPercentage}%`
   });
 };
+
+// get image stream from server and set UI
 faye.subscribe('/drone/image', src => $('#cam').attr({ src: src }));
 
-keymap = {
+// get keyinput
+const keymap = {
   87: { ev: 'move', action: 'front' }, // W
   83: { ev: 'move', action: 'back' }, // S
   65: { ev: 'move', action: 'left' }, // A
@@ -64,6 +68,8 @@ $(document).keyup(ev => {
   speed = 0;
   faye.publish('/drone/drone', { action: 'stop' });
 });
+
+// get mouse event
 $('*[data-action]').on('mousedown', ev => {
   faye.publish('/drone/' + $(this).attr('data-action'), {
     action: $(this).attr('data-param'),

server.js

@@ -2,9 +2,11 @@ const express = require('express');
 const faye = require('faye');
 const path = require('path');
 
+// config drone
 const drone = require('ar-drone').createClient();
 drone.config('general:navdata_demo', 'TRUE');
 
+// config express app
 const app = express();
 app.configure(() => {
   app.set('port', process.env.PORT || 3001);
@@ -13,11 +15,12 @@ app.configure(() => {
   app.use('/components', express.static(path.join(__dirname, 'components')));
 });
 
+// create server and socket
 const server = require('http').createServer(app);
-
 new faye.NodeAdapter({ mount: '/faye', timeout: 45 }).attach(server);
 const socket = new faye.Client(`http://localhost:${app.get('port')}/faye`);
 
+// get request from socket -> set command to drone
 socket.subscribe('/drone/move', cmd => {
   console.log('move', cmd);
   if (drone[cmd.action]) drone[cmd.action](cmd.speed);
@@ -30,13 +33,17 @@ socket.subscribe('/drone/drone', cmd => {
   console.log('drone command: ', cmd);
   if (drone[cmd.action]) drone[cmd.action]();
 });
+
+// start server
 server.listen(app.get('port'), () =>
   console.log('Express server listening on port ' + app.get('port'))
 );
 
-let currentImg = null;
+// send navdata to socket
 drone.on('navdata', data => socket.publish('/drone/navdata', data));
 
+// save latest img from drone PngStream
+let currentImg = null;
 let imageSendingPaused = false;
 drone.createPngStream().on('data', frame => {
   currentImg = frame;
@@ -48,6 +55,7 @@ drone.createPngStream().on('data', frame => {
   }, 100);
 });
 
+// send latest img to server
 app.get('/image/:id', (req, res) => {
   res.writeHead(200, { 'Content-Type': 'image/png' });
   res.end(currentImg, 'binary');