Real-Time Geolocation Service with Node.js

A tutorial about how to create a simple real-time application that shows the locations of visitors on an interactive map using Node.js and the HTML5 Geolocation API.
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Real-Time Geolocation Service with Node.js
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Hi guys! In today’s tutorial we will make a simple real-time application that will determine and show the locations of currently connected users directly on a map. For this purpose we will use Node.js and the HTML5 Geolocation API. As you may know node.js is an asynchronous web server which is built on the Google V8 JavaScript engine and is a perfect solution as a back-end for real-time apps. Our app will let users see each other on the map with the help of the socket.io library that uses Web Sockets (and its alternatives like AJAX long polling for older browsers – more) for a real-time data channel. Our example will work in all modern browsers that support the HTML5 Geolocation API.

Please note: this only works as intended in browsers that properly support the HTML features in use.

Installing node

First, you’ll need to install node.js. You can get pre-compiled Node.js binaries for several platforms from the download section of the official website: http://nodejs.org/download.
After the installation is complete you will get access to the node package manager (npm), with the help of which we will install all needed modules for this tutorial. We will use socket.io and node-static, which will serve all the client side files with ease. Go to the directory of your app and run this command in your terminal or command line:

npm install socket.io node-static

Tip: I advice you to install a utility like nodemon that will keep an eye on your files and you won’t need to restart your server after every change:

npm install nodemon -g

“-g” means that it will be installed globally and accessible from every node repo.

The HTML

Let’s first create an “index.html” in our public directory.

<!doctype html>
<html>

	<head>
		<meta charset="utf-8">
		<meta name="author" content="Dmitri Voronianski">
		<title>Real-Time Geolocation with Web Sockets</title>
		<link href='http://fonts.googleapis.com/css?family=Lato:300,400' rel='stylesheet' type='text/css'>
		<link rel="stylesheet" href="./css/styles.css">
		<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.4/leaflet.css" />

		<!--[if lt IE 9]>
			<script src="//html5shim.googlecode.com/svn/trunk/html5.js"></script>
		<![endif]-->
	</head>

	<body>
		<div class="wrapper">
		  <header>
		  	<h1>Real-Time Geolocation Service with Node.js</h1>
		  	<div class="description">Using HTML5 Geolocation API and Web Sockets to show connected locations.</div>
		  </header>

		  <div class="app">
		  	<div class="loading"></div>
		  	<div id="infobox" class="infobox"></div>
		  	<div id="map">To get this app to work you need to share your geolocation.</div>
		  </div>
		</div>

		<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>
		<script src="./js/lib/leaflet.js"></script>
		<script src="/socket.io/socket.io.js"></script>
		<script src="./js/application.js"></script>
	</body>

</html>

As you can see it’s pretty simple. For rendering our map on the page we will use an incredible open-source JavaScript library for interactive maps – Leaflet.js. It’s free and highly customizable. The API documentation is available on the website. Our styles.css file is inside the “./public/css/” folder. It will include some simple styles for the app. The leaflet.css in the same folder contains the styles for the map.

Server side

Now we are ready to start with the back-end of our app. Let’s take a look at “server.js”:

// including libraries
var http = require('http');
var static = require('node-static');
var app = http.createServer(handler);
var io = require('socket.io').listen(app);

// define port
var port = 8080;

// make html, js & css files accessible
var files = new static.Server('./public');

// serve files on request
function handler(request, response) {
	request.addListener('end', function() {
		files.serve(request, response);
	});
}

// listen for incoming connections from client
io.sockets.on('connection', function (socket) {

  // start listening for coords
  socket.on('send:coords', function (data) {

  	// broadcast your coordinates to everyone except you
  	socket.broadcast.emit('load:coords', data);
  });
});

// starts app on specified port
app.listen(port);
console.log('Your server goes on localhost:' + port);

The code is not complicated at all; everything that it does is serving files and listening to the data from the client. Now we can start our app from the terminal or command line and take a look:

node server.js

Or, if you have followed my advice and used nodemon, write this:

nodemon server.js

Now go to localhost:8080 in your browser (you can change the port to whatever you like). Everything will be static because our main JavaScript function is not ready, yet.

The Client Side

It’s time to open the “./public/js/application.js” file and to write a couple of functions (we’ll be using jQuery):

$(function() {
	// generate unique user id
	var userId = Math.random().toString(16).substring(2,15);
	var socket = io.connect("/");
	var map;

	var info = $("#infobox");
	var doc = $(document);

	// custom marker's icon styles
	var tinyIcon = L.Icon.extend({
		options: {
			shadowUrl: "../assets/marker-shadow.png",
			iconSize: [25, 39],
			iconAnchor:   [12, 36],
			shadowSize: [41, 41],
			shadowAnchor: [12, 38],
			popupAnchor: [0, -30]
		}
	});
	var redIcon = new tinyIcon({ iconUrl: "../assets/marker-red.png" });
	var yellowIcon = new tinyIcon({ iconUrl: "../assets/marker-yellow.png" });

	var sentData = {}

	var connects = {};
	var markers = {};
	var active = false;

	socket.on("load:coords", function(data) {
		// remember users id to show marker only once
		if (!(data.id in connects)) {
			setMarker(data);
		}

		connects[data.id] = data;
		connects[data.id].updated = $.now(); // shorthand for (new Date).getTime()
	});

	// check whether browser supports geolocation api
	if (navigator.geolocation) {
		navigator.geolocation.getCurrentPosition(positionSuccess, positionError, { enableHighAccuracy: true });
	} else {
		$(".map").text("Your browser is out of fashion, there's no geolocation!");
	}

	function positionSuccess(position) {
		var lat = position.coords.latitude;
		var lng = position.coords.longitude;
		var acr = position.coords.accuracy;

		// mark user's position
		var userMarker = L.marker([lat, lng], {
			icon: redIcon
		});

		// load leaflet map
		map = L.map("map");

		// leaflet API key tiler
		L.tileLayer("http://{s}.tile.cloudmade.com/BC9A493B41014CAABB98F0471D759707/997/256/{z}/{x}/{y}.png", { maxZoom: 18, detectRetina: true }).addTo(map);
		
		// set map bounds
		map.fitWorld();
		userMarker.addTo(map);
		userMarker.bindPopup("
You are there! Your ID is " + userId + "
").openPopup();

		// send coords on when user is active
		doc.on("mousemove", function() {
			active = true; 

			sentData = {
				id: userId,
				active: active,
				coords: [{
					lat: lat,
					lng: lng,
					acr: acr
				}]
			}
			socket.emit("send:coords", sentData);
		});
	}

	doc.bind("mouseup mouseleave", function() {
		active = false;
	});

	// showing markers for connections
	function setMarker(data) {
		for (i = 0; i < data.coords.length; i++) {
			var marker = L.marker([data.coords[i].lat, data.coords[i].lng], { icon: yellowIcon }).addTo(map);
			marker.bindPopup("
One more external user is here!
");
			markers[data.id] = marker;
		}
	}

	// handle geolocation api errors
	function positionError(error) {
		var errors = {
			1: "Authorization fails", // permission denied
			2: "Can't detect your location", //position unavailable
			3: "Connection timeout" // timeout
		};
		showError("Error:" + errors[error.code]);
	}

	function showError(msg) {
		info.addClass("error").text(msg);
	}

	// delete inactive users every 15 sec
	setInterval(function() {
		for (ident in connects){
			if ($.now() - connects[ident].updated > 15000) {
				delete connects[ident];
				map.removeLayer(markers[ident]);
			}
        }
    }, 15000);
});

Magic happens when we use socket.emit to send a message to our node web server on every mouse move. It means that our user is active on the page. We also receive the data from the server with socket.on and after getting initialize markers on the map. The main things that we need for the markers are the latitude and longitude which we receive from the browser. If the user is inactive for more then 15 seconds we remove their marker from our map. If the user’s browser doesn’t support the Geolocation API we’ll show a message that the browser is out-of-date. You can read more about the HTML5 Geolocation API here: Geolocation – Dive Into HTML5.

Demo Repository

You can take a look at the whole app in my github repo, clone it and experiment with it locally. If you have questions feel free to ask in the comments or you can also e-mail me. Thanks!

Please note that the demo might not load properly sometimes due to server overload.

Tagged with:

Dmitri Voronianski

Dmitri is a young front-end developer based in Kiev, Ukraine. He is absolutely passionate about Javascript and modern HTML5, CSS3 coolness too.

http://pixelhunter.me

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Comments are closed.

  3. Is ist somehow possible to get the map tiles from cloudmade or any other provider via https?
    Or do you know a working php proxy for this?

    • Heroku does not work with websockets, but the socket.io library falls back to XHR long polling, which does work.

  7. when i view this on an iphone 4 i receive: “error: Authorization fails” – why would this be? Works on desktop however

  8. Hi Dimitri,

    Great to share your work. Do you think it works with watchPosition function ? if user has GPS mobile device, is the marker moving ?

    Tx
    Flo

  11. can we do this without requesting permission of user to allow, if not can we have it as a custom message not browser message… as users might not know how to use.

  13. Hi Dimitri, thank you for sharing that cool stuff. I’m trying to install it on my server for testing it and I have a few problem with the socket.io package (I have correctly installed socket.io in node). Everytime I tried to run my webpage it says that “require is not defined” in this line:
    var client = require(‘socket.io-client’);
    in the file “socket.io.js”.
    So correct me if i’m wrong but this require is a part of ressources that my node server run, isn’t it ?
    I’m sur that my node server is running and have correctly lauch the socket.io ressources.
    Is this talk to you ?

    Thank you

    • It’s strange but it maybe caused of your node version, is it 0.10.x? But nevertheless I already fixed this cross version issues in my demo repo at github. So my advice is to do everything from scratch again:

      1. clone repo
      2. go to repo
      3. run “npm install“
      4. run “node server.js“
      5. go to localhost:8080 – everything should be ok

      Or let me know if there’s something wrong again.

  15. I followed the same steps as per your documentation.
    I am unable to see the map.

    Can you please explain the code in application.js
    L.tileLayer(‘https://{s}.tiles.mapbox.com/v3/examples.map-i87786ca/{z}/{x}/{y}.png’, { maxZoom: 18, detectRetina: true }).addTo(map);

    I’m getting the following ERRORS:-
    https://a.tiles.mapbox.com/v3/examples.map-i87786ca/1/0/0.png 404 (Not Found)
    https://b.tiles.mapbox.com/v3/examples.map-i87786ca/1/1/0.png 404 (Not Found)
    https://b.tiles.mapbox.com/v3/examples.map-i87786ca/1/0/1.png 404 (Not Found)
    https://c.tiles.mapbox.com/v3/examples.map-i87786ca/1/1/1.png 404 (Not Found)

  16. Hi Dimitri,

    Map is not loading icon is loading . Click event also not working . HTML 5 loader problem?

    Thanks
    Sat