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:pm 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.jsOr, if you have followed my advice and used nodemon, write this:
nodemon server.jsNow 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.
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