A secure OpenVidu sample app with a Node backend and a SPA frontend. It makes use of the openvidu-node-client to get the necessary params from OpenVidu Server.

Understanding this example

OpenVidu is composed by the modules displayed on the image above.

openvidu-browser: JavaScript library for the browser. It allows you to manage your video-calls straight away from your clients
openvidu-node-client: NPM package to easily get the necessary params (sessionId's and tokens) from openvidu-server. Quick alternative to REST API
openvidu-server: Java application that controls Kurento Media Server
Kurento Media Server: server that handles low level operations of media flow transmissions

You will only have to make use of openvidu-browser and openvidu-node-client to get this sample app working

Executing this example

Clone the repo:

git clone https://github.com/OpenVidu/openvidu-tutorials.git

You will need node and NPM to execute the app. You can install them with:
```
sudo apt-get install nodejs
sudo apt-get install npm
```
To run the sample application, execute the following commands in the project. They will install the NPM dependencies and will execute server.js server passing two arguments: "localhost:8443" as the URL where openvidu-server will be listening and "MY_SECRET" as the secret share with it:
```
cd openvidu-js-node
npm install
node server.js localhost:8443 MY_SECRET
```
openvidu-server and Kurento Media Server must be up and running in your development machine. The easiest way is running this Docker container which wraps both of them (you will need Docker CE):
```
docker run -p 8443:8443 --rm -e KMS_STUN_IP=193.147.51.12 -e KMS_STUN_PORT=3478 -e openvidu.secret=MY_SECRET openvidu/openvidu-server-kms
```
Go to https://localhost:5000 to test the app once the server is running. The first time you use the docker container, an alert message will suggest you accept the self-signed certificate of openvidu-server when you first try to join a video-call. To test two users in the same computer, use a standard window and an incognito window.

Understanding the code

This is a very basic web application with a pretty simple vanilla JS/HTML/CSS frontend and a straightforward Node backend with express. OpenVidu assumes you can identify your users so you can tell which users can connect to which video-calls, and what role (and therefore what permissions) each one of them will have in the calls. You can do this as you prefer. Here our backend will manage the users and their sessions with the easy-to-use and non-intrusive express-session API.

Backend: node server
- server.js : single file which handles all operations of server.
Frontend: Pure JS/HTML/CSS files (/public folder)
- OpenVidu.js : openvidu-browser library. You don't have to manipulate this file.
- app.js : sample application main JavaScritp file, which makes use of OpenVidu.js.
- index.html : HTML code for the form to login, the form to connect to a video-call and for the video-call itself. It has two links to both JavaScript files:
```
<script src="OpenVidu.js"></script>
<script src="app.js"></script>
```
- style.css: some CSS classes to style index.html.

Let's describe the code following this scenario: a user logs in to the app and connects to the video-call "TUTORIAL", where he publishes his webcam. A second user will connect to the same video-call just after that and publish its own webcam. Both of them will leave the call after a while.

1) User logs in

We have implemented a method for making HTTP requests to the backend, as we will need to make at least three of them: one for logging in, one for getting the sessionId and a valid token from openvidu-server and one for letting know our backend when any user leaves the video-call. The header of the method looks like this:

function httpRequest(method, url, body, errorMsg, callback)

Where method is whether "POST" or "GET", url the path of the REST operation, body the data to be passed, errorMsg the output error message if something goes wrong and callback the function to execute in case of success. As mentioned above, we need to call this method three times for each user that LOGS IN 🡒 CONNECTS TO A VIDEO-CALL 🡒 LEAVES THE VIDEO-CALL.

index.html will first show a form to log in:

app.js sends an HTTP request to "/api-login/login" passing the username and the password retrieved from the HTML form whenever "Log in" button is clicked:

function logIn() {
	var user = $("#user").val(); // Username
	var pass = $("#pass").val(); // Password
	var jsonBody = JSON.stringify({ // Body of POST request
		'user': user,
		'pass': pass
	});

	httpRequest('POST', '/api-login/login', jsonBody, 'Login WRONG',
	  function successCallback(response){ // Send POST request
		console.warn(userName + ' login');
		// HTML shows logged-in page ...
	});
}

server.js at /api-login/login checks the params are correct and if so sets an active session for the newly logged user (adding a loggedUser property with its username in the req.session object):

app.post('/api-login/login', function (req, res) {
    
    // Retrieve params from POST body
    var user = req.body.user;
    var pass = req.body.pass;

    if (login(user, pass)) { // Correct user-pass
        // Validate session and return OK 
        // Value stored in req.session allows us to identify the user in future requests
        req.session.loggedUser = user;
        res.status(200).send();
    } else { // Wrong user-pass
        // Invalidate session and return error
        req.session.destroy();
        res.status(401).send('User/Pass incorrect');
    }
});

2) User connects to "TUTORIAL" video-call

HTML will display now the user has logged a different form, asking for the video-call to connect and the nickname the user wants to have in it. So our 'publisher1' user would write TUTORIAL in "Session" field and press "Join!" button:

app.js will execute joinSession() method, which starts like this:

function joinSession() {
	getSessionIdAndToken(function () { ...

So the first thing to do here is to retrieve a sessionId and a token from our backend. Only when we have them available in the browser we will continue with the join operation. Let's see what getSessionIdAndToken() looks like:

function getSessionIdAndToken(callback) {
	sessionName = $("#sessionName").val(); // Video-call to connect ("TUTORIAL")
	var jsonBody = JSON.stringify({ // Body of POST request
		'session': sessionName
	});

	// Send POST request
	httpRequest('POST', '/api-sessions/get-sessionid-token', jsonBody, 
	 'Request of SESSIONID and TOKEN gone WRONG:', function successCallback(response){
		sessionId = response[0]; // Get sessionId from response
		token = response[1]; // Get token from response
		callback(); // Continue the join operation
	});
}

Here is the second time we must call our httpRequest() method, sending the session we want to connect ("TUTORIAL") and waiting to get a sessionId and a token as response. The interesting part here is in server.js controller at /api-sessions/get-sessionid-token. First of all there are some important attributes in this class we must mention:

// Environment variable: URL where our OpenVidu server is listening
var OPENVIDU_URL = process.argv[2];
// Environment variable: secret shared with our OpenVidu server
var OPENVIDU_SECRET = process.argv[3];

// OpenVidu object to ask openvidu-server for sessionId and token
var OV = new OpenVidu(OPENVIDU_URL, OPENVIDU_SECRET);

// Collection to pair session names and OpenVidu Session objects
var mapSessionNameSession = {};
// Collection to pair sessionId's (identifiers of Session objects) and tokens
var mapSessionIdTokens = {};

Rest controller method begins retrieving the param send by the client, which in this case is the video-call name ("TUTORIAL"), as well as preparing a param we will need a little further on: tokenOptions.

app.post('/api-sessions/get-sessionid-token', function (req, res) {
	// Check the user is logged ... 

	// The video-call to connect ("TUTORIAL")
	var sessionName = req.body.session;

	// Role associated to this user
	var role = users.find(u => (u.user === req.session.loggedUser)).role;

	// Optional data to be passed to other users when this user connects to the video-call
	// In this case, a JSON with the value we stored in the req.session object on login
	var serverData = '{"serverData": "' + req.session.loggedUser + '"}';

	// Build tokenOptions object with the serverData and the role
	var tokenOptions = new TokenOptions.Builder()
           .data(serverData)
           .role(role)
           .build();

Just after that an if-else statement comes into play: does the session "TUTORIAL" already exitsts?

if (mapSessionNameSession[sessionName]) { ...

In this case it doesn't because 'publisher1' is the first user connecting to it. So we focus on the else branch:

else { // New session: return a new sessionId and a new token
	// Create a new OpenVidu Session
	var mySession = OV.createSession();
	
	// Get the sessionId asynchronously
	mySession.getSessionId(function (sessionId) {
		
		// Store the new Session in the collection of Sessions
		mapSessionNameSession[sessionName] = mySession;
		// Store a new empty array in the collection of tokens
		mapSessionIdTokens[sessionId] = [];
		
		// Generate a new token asynchronously with the recently created tokenOptions
		mySession.generateToken(tokenOptions, function (token) {
			
			// Store the new token in the collection of tokens
			mapSessionIdTokens[sessionId].push(token);
			
			// Return the sessionId and token to the client
			res.status(200).send({
				0: sessionId,
				1: token
			});
		});
	});
}

We are almost there! Now in app.js we can init a new Session with sessionId and connect to it with token:

// --- 1) Get an OpenVidu object and init a session with the retrieved sessionId ---

OV = new OpenVidu();
session = OV.initSession(sessionId);


// --- 2) Specify the actions when events take place ---

// On every new Stream received...
session.on('streamCreated', function (event) {

	// Subscribe to the Stream to receive it
	// HTML video will be appended to element with 'subscriber' id
	var subscriber = session.subscribe(event.stream, 'subscriber');
	
	// When the HTML video has been appended to DOM...
	subscriber.on('videoElementCreated', function (event) {
	
		// Add a new <p> element for the user's name and nickname just below its video
		appendUserData(event.element, subscriber.stream.connection);
	});
});

// On every Stream destroyed...
session.on('streamDestroyed', function (event) {
	// Delete the HTML element with the user's name and nickname
	removeUserData(event.stream.connection);
});


// --- 3) Connect to the session passing the retrieved token and some more data from
//         the client (in this case a JSON with the nickname chosen by the user) ---

session.connect(token, '{"clientData": "' + $("#participantName").val() + '"}', function (err) {

	// If the connection is successful, initialize a publisher and publish to the session
	if (!err) {

		// Here we check somehow if the user has at least 'PUBLISHER' role before
		// trying to publish its stream. Even if someone modified the client's code and
		// published the stream, it wouldn't work if the token sent in Session.connect
		// method doesn't belong to a 'PUBLIHSER' role
		if (isPublisher()) {

			// --- 4) Get your own camera stream ---

			var publisher = OV.initPublisher('publisher', {
				audio: true,
				video: true,
				quality: 'MEDIUM'
			});


			// --- 5) Publish your stream ---

			session.publish(publisher);

		} else {
			console.warn('You don\'t have permissions to publish');
		}
	} else {
		console.warn('Error connecting to the session:', error.code, error.message);
	}
	
	// HTML shows session page ...
	
});

The user will now see its own video on the page. The connection to the session has completed!

3) Another user connects to the video-call

The process would be exactly the same as before until server.js executes controller at /api-sessions/get-sessionid-token. Now session 'TUTORIAL' already exists, so in the if-else statement the if branch would be the one executed:

if (mapSessionNameSession[sessionName]) {
	// Session already exists: return existing sessionId and a new token
	
	// Get the existing Session from the collection
	var mySession = mapSessionNameSession[sessionName];
	
	// Generate a new token asynchronously with the recently created tokenOptions
	mySession.generateToken(tokenOptions, function (token) {
		
		// Get the existing sessionId
		var sessionId = mySession.getSessionId();
		
		// Store the new token in the collection of tokens
		mapSessionIdTokens[sessionId].push(token);
		
		// Return the sessionId and token to the client
		res.status(200).send({
			0: sessionId,
			1: token
		});
	});
}

The code executed in app.js would also be the same. After the Session.publish() method has been succesful, both users will be seeing each other's video, as well as the username and the nickname below it.

4) Users leave the video-call

After a while both users decide to leave the session. Apart from calling leaveSession() (and therefore session.disconnect()) to destroy the connection on openvidu-server, we need to run the last HTTP operation: we must let the backend know that certain user has left the session so it can update the collections with the active sessions and tokens. To sum up, session.disconnect() updates our openvidu-server and the POST operation updates our backend. For the POST operation, in app.js we run:

function removeUser() {
	// Body of POST request with the name of the session and the token of the leaving user
	var jsonBody = JSON.stringify({
		'sessionName': sessionName,
		'token': token
	});

	// Send POST request
	httpRequest('POST', '/api-sessions/remove-user', jsonBody,
		'User couldn\'t be removed from session', function successCallback(response) {
		console.warn(userName + ' correctly removed from session ' + sessionName);
	});
}

And in server.js we update the collections in /api-sessions/remove-user:

app.post('/api-sessions/remove-user', function (req, res) {
	// Check the user is logged ...
	
	// Retrieve params from POST body
	var sessionName = req.body.sessionName;
	var token = req.body.token;
	
	// If the session exists ("TUTORIAL" in this case)
	var mySession = mapSessionNameSession[sessionName];
	if (mySession) {
		var tokens = mapSessionIdTokens[mySession.getSessionId()];
		if (tokens) {
			var index = tokens.indexOf(token);
			
			// If the token exists
			if (index !== -1) {
				// Token removed!
				tokens.splice(index, 1);
			} else {
				res.status(500).send('The TOKEN wasn\'t valid');
			}
			if (mapSessionIdTokens[mySession.getSessionId()].length == 0) {
				// Last user left: session "TUTORIAL" must be removed
				delete mapSessionNameSession[sessionName];
			}
			res.status(200).send();
		} else {
			res.status(500).send('The SESSIONID wasn\'t valid');
		}
	} else {
		res.status(500).send('The SESSION does not exist');
	}
}

When the last user leaves the session delete mapSessionNameSession[sessionName] will be executed: this means the session is empty and that it is going to be closed. The sessionId and all token params associated to it will be invalidated.

At this point we have covered all the important code from the tutorial. With this scenario we have seen the most common use-case, but you can modify whatever you want to suit your needs. And remember that this is just one of the many possible approaches: you can implement your frontend and your backend as you want.

The only actual requirements are getting sessionId and token params from openvidu-server (by using one of the available clients or with the REST API) and using them along with openvidu-browser to connect your clients to the sessions.