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OpenTok Hello World .NET

This is a simple demo app that shows how you can use the OpenTok .NET SDK to create Sessions, generate Tokens with those Sessions, and then pass these values to a JavaScript client that can connect and conduct a group chat.

Note: These instructions assume you will be using Visual Studio. Since the application runs as a self hosted OWIN-compatible console application, you have two options to run this sample:

  • Open Visual Studio using 'Run as administrator'.
  • Use your current user to run Visual Studio but reserve the url by running this command from a Administrator Command Prompt: netsh http add urlacl url=http://+:8080/ user=DOMAIN\USERNAME

The sample projects are contained inside the OpenTok.sln solution at the top level.

Running the App

First, add your own API Key and API Secret to the Application Settings. For your convenience, the App.config file is set up for you to place your values into it.

    <add key="API_KEY" value="000000" />
    <add key="API_SECRET" value="abcdef1234567890abcdef" />

Next, make sure the HelloWorld project is set as the Solution's Startup project. This can be done by opening the Properties of the solution, and selecting it under Common Properties > Startup Project.

Lastly, the dependencies of the application are referenced using NuGet. Package Restore is a feature of NuGET 2.7+ and as long as your installation of Visual Studio has the NuGet extension installed with a later version, the package should be installed automatically on launch. Otherwise, use the NuGET Packge Restore guide.

Choose Start (Ctrl+F5) to run the application.

Visit http://localhost:8080 in your browser. Open it again in a second window. Smile! You've just set up a group chat.


This demo application uses the Nancy micro web framework. It is similar to many other popular web frameworks. We are only covering the very basics of the framework, but you can learn more by following the link above.

Bootstrapper (Bootstrapper.cs)

Nancy uses Dependency Injection in order to initialize important objects that will remain alive for the lifetime of the application, in an IoC (Inversion of Control) Container. In order to configure that container, the DefaultNancyBootstrapper class is subclassed and the ConfigureApplicationContainer() method is overridden.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Nancy;

namespace HelloWorld
    public class Bootstrapper : DefaultNancyBootstrapper
        protected override void ConfigureApplicationContainer(Nancy.TinyIoc.TinyIoCContainer container)


Once the super class is given a chance to configure, a new object of type OpenTokService is registered into the container as a singleton. The IoC Container is then responsible for creating the (one and only one) OpenTokService instance and making it available to other parts of the application.

OpenTok Service (OpenTokService.cs)

This object provides its very simple functionality as a service to the rest of the application. Its only responsibility is to initialize a couple OpenTok related objects and make them visible any part of the application that needs them.

public class OpenTokService
    public Session Session { get; protected set; }
    public OpenTok OpenTok { get; protected set; }

    public OpenTokService()
        int apiKey = 0;
        string apiSecret = null;
            string apiKeyString = ConfigurationManager.AppSettings["API_KEY"];
            apiSecret = ConfigurationManager.AppSettings["API_SECRET"];
            apiKey = Convert.ToInt32(apiKeyString);

        catch (Exception ex)
            if (!(ex is ConfigurationErrorsException || ex is FormatException || ex is OverflowException))
                throw ex;

            if (apiKey == 0 || apiSecret == null)
                    "The OpenTok API Key and API Secret were not set in the application configuration. " +
                    "Set the values in App.config and try again. (apiKey = {0}, apiSecret = {1})", apiKey, apiSecret);

        this.OpenTok = new OpenTok(apiKey, apiSecret);

        this.Session = this.OpenTok.CreateSession();

This class simply has the default constructor (called by the IoC Container) and two public properties with protected setters. In the constructor, the application configuration is read to retrieve an API Key and an API Secret. If those settings are not available, an exception is thrown and an appropriate error message is written to the console. Then the API Key and API Secret are used to initialize and instance of OpenTok, which is stored into the one of the public properties.

Now, lets discuss the Hello World application's functionality. We want to set up a group chat so that any client (user in a browser) that visits a page will connect to the same OpenTok Session. Once they are connected they can Publish a Stream and Subscribe to all the other streams in that Session. So we just need one Session object, and the OpenTokService can be used to make it accessible. The next line of our application simply calls the OpenTok instance's CreateSession() method and stores the resulting Session object in the other public property. Alternatively, for applications that have many Sessions, the Id property of a Session can be stored in a database and used for all of the same operations that can be done with the instance (using slightly different API).

Main Module (MainModule.cs)

In a Nancy application, any subclasses of NancyModule are initialized by the framework and given the opportunity to respond to requests using route matching. This class's dependencies are expressed as arguments to the constructor, which the IoC Container will fill in the right instance, such as an instance of OpenTokService as we need in this Module.

As we've discussed already, since we want any user who comes to the application to be placed into one group chat, we only need one page. So we create one route handler for any HTTP GET requests to trigger, which is done by using just the "/" as the route.

public class MainModule : NancyModule

    public MainModule(OpenTokService opentokService)

        Get["/"] = _ =>
                // ...

Now all we have to do is serve a page with the three values the client will need to connect to the session: ApiKey, SessionId, and Token. The first two are available from the OpenTokService: the ApiKey is a property on the OpenTok instance, and the SessionId is a property on the Session instance. The Token is generated freshly on this request by calling the Session instance's GenerateToken() method. This is because a Token is a piece of information that carries a specific client's permissions in a certain Session. Ideally, as we've done here, you generate a unique token for each client that will connect.

These three values can be stored in a model, and then passed to the View rendering system. Here we've chosen to use a dynamic ExpandoObject instead of strongly typing the model, for our convenience.

        // ...
        Get["/"] = _ =>
                dynamic locals = new ExpandoObject();

                locals.ApiKey = opentokService.OpenTok.ApiKey.ToString();
                locals.SessionId = opentokService.Session.Id;
                locals.Token = opentokService.Session.GenerateToken();

                return View["index", locals];
        // ...

The View rendering system will find a template named "index" and combine it with the data in the locals object to create a response to send back to the browser.

Main Template (views/index.sshtml)

This file simply sets up the HTML page for the JavaScript application to run, imports the OpenTok.js JavaScript library, and passes the values created by the server into the JavaScript application inside Content/js/helloworld.js

JavaScript Applicaton (Content/js/helloworld.js)

The group chat is mostly implemented in this file. At a high level, we connect to the given Session, publish a stream from our webcam, and listen for new streams from other clients to subscribe to.

For more details, read the comments in the file or go to the JavaScript Client Library for a full reference.

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