Use the Sinch JavaScript SDK in Your Servlet Project

This tutorial will focus mostly on authentication; after that, the implementation in your HTML and JavaScript files is the same as the sample projects included in the SDK.

Sinch setup

  1. Sign up for a Sinch account
  2. In the developer dashboard, create a new app and take note of the app key and secret
  3. Download the Sinch JavaScript SDK

Create the user ticket

Create a new servlet project with one servlet for authentication that has a doPost method:

public class AuthServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public AuthServlet() {

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // If you want to authenticate user,
    // generate a ticket to pass to the Sinch Client

Next, create the login/signup form view that will send a post request to the doPost method above. (Ideally, you would have more of a distinction between logging in and signing up, but I’ll leave that to you to best implement with your existing user database.)

Create a file called index.jsp (or index.html) in the WebContent directory. This will be a simple username and password form:

<form action="authenticate" method="post">
    Username: <input type="text" name="username" /><br>
    Password: <input type="password" name="password" /><br>
    <input type="submit" value="Login/Signup"/>

Now, let’s generate the ticket in doPost. First, define several variables that you will use to create the ticket. (Be sure to sub in your app key and secret.):

int expiresIn = 3600; //seconds
String applicationKey = "YOUR_APP_KEY"; //change me!
String applicationSecret = "YOU_APP_SECRET"; //change me!

//date in iso8601 format
Date date= new java.util.Date();
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
String timestamp = dateFormat.format(date);

//user-submitted username and password
String username = request.getParameter("username");
String password = request.getParameter("password");

Next, create the ticket and store it in the session object, which you can access from the view:

String userTicket = "{\"identity\":{\"type\":\"username\""
            + ",\"endpoint\":\"" + username + "\"},\"expiresIn\":"
            + expiresIn + ",\"applicationKey\":\"" + applicationKey
            + "\",\"created\":\"" + timestamp + "\"}";

String userTicketBase64 = Base64.encodeBase64String(userTicket.getBytes());

String signature = "";
try {
    Mac sha256HMAC = Mac.getInstance("HmacSHA256");
    SecretKeySpec secretKey = new SecretKeySpec(Base64.decodeBase64(applicationSecret.getBytes()), "HmacSHA256");
       signature = Base64.encodeBase64String(sha256HMAC.doFinal(userTicket.getBytes()));
} catch (Exception e) {

HttpSession session = request.getSession();
session.setAttribute("ticket", userTicketBase64 + ":" + signature);
response.sendRedirect("success.jsp"); //still need to create this file

Note: This will authenticate any username/password combination. Before generating the ticket, you need to check the username/password combo against your database of users.

Add the Sinch SDK

First, create a success.jsp file, where doPost redirects to.

To add the Sinch SDK, just move sinch.min.js to your WebContent folder. Then simply include the JavaScript file in the head of success.jsp:

//while you're at it, add jquery too!
<script src=""></script>
<script src="sinch.min.js"></script>

To keep things simple, I put the script to start the Sinch client inside my success.jsp file. Here, you will get the token from the session:

  $('document').ready(function() {

    //define the sinch client
    sinchClient = new SinchClient({
      applicationKey: "YOUR_APP_KEY", //change me!
      capabilities: {calling:true, messaging: true}, //only use what you need here
      startActiveConnection: true,
      onLogMessage: function(message) {
        //messages appended to the body when
        //the state of the client changes
        $("body").append("<p>" + message.message + "</p>");

    //here's that user ticket!
    sinchClient.start({"userTicket":"<%= session.getAttribute("ticket").toString() %>"})
      .then(function() {
        //now, you can start using the client to make calls & send messages
        $("body").append("<p>SinchClient is started!</p>");
      }); //handle error if no ticket, or ticket is no longer valid

When running this in your browser, after logging in, you will see the changes in client state as HTML like so:

screenshot of working application

Congratulations, you did it! You can now use the Sinch client to add calling or messaging to your web app. Check out the following tutorials to continue with your app: