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Making and Receiving Calls from the Browser

As of 2016-08-29, the Twilio quickstart docs do not contain examples for Elixir. Some examples for Elixir can be found in this tutorial.

To begin, create an empty Phoenix application called Demo and install and configure ExTwilio per the instructions on the README.

Making a Call

Create a controller with a show action, and generate a Twilio capability token with the specified application sid (it plays a welcome message)

defmodule Demo.TwilioController do
  use Demo.Web, :controller

  def show(conn, _params) do
    token =
      ExTwilio.Capability.new
      |> ExTwilio.Capability.allow_client_outgoing("APabe7650f654fc34655fc81ae71caa3ff")
      |> ExTwilio.Capability.token

    render(conn, "show.html", token: token)
  end
end

Create a view template for the show action

<script type="text/javascript"
  src="//media.twiliocdn.com/sdk/js/client/v1.3/twilio.min.js"></script>
<script type="text/javascript"
  src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js">
</script>
<script type="text/javascript">

/* Create the Client with a Capability Token */
Twilio.Device.setup("<%= @token %>", {debug: true});

/* Let us know when the client is ready. */
Twilio.Device.ready(function (device) {
    $("#log").text("Ready");
});

/* Report any errors on the screen */
Twilio.Device.error(function (error) {
    $("#log").text("Error: " + error.message);
});

Twilio.Device.connect(function (conn) {
    $("#log").text("Successfully established call");
});

/* Log a message when a call disconnects. */
Twilio.Device.disconnect(function (conn) {
    $("#log").text("Call ended");
});

/* Connect to Twilio when we call this function. */
function call() {
    Twilio.Device.connect();
}

/* A function to end a connection to Twilio. */
function hangup() {
    Twilio.Device.disconnectAll();
}
</script>

<button class="call" onclick="call();">
  Call
</button>

<!-- use an onclick action to hang up the call when the user presses
the button -->
<button class="hangup" onclick="hangup();">
  Hangup
</button>
<div id="log"></div>

Start Phoenix and open the page in the browser. Click the Call button and you should hear the Twilio welcome message.

Receiving a Call

Create a controller with a show action and generate a Twilio capability token with the name jenny, which will allow Jenny to receive incoming calls

defmodule Demo.TwilioController do
  use Demo.Web, :controller

  def show(conn, _params) do
    token =
      ExTwilio.Capability.new
      |> ExTwilio.Capability.allow_client_incoming("jenny")
      |> ExTwilio.Capability.token

    render(conn, "show.html", token: token)
  end
end

Create a view template for the show action

<script type="text/javascript"
  src="//media.twiliocdn.com/sdk/js/client/v1.3/twilio.min.js"></script>
<script type="text/javascript"
  src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js">
</script>
<script type="text/javascript">

/* Create the Client with a Capability Token */
Twilio.Device.setup("<%= @token %>", {debug: true});

/* Let us know when the client is ready. */
Twilio.Device.ready(function (device) {
    $("#log").text("Ready");
});

/* Report any errors on the screen */
Twilio.Device.error(function (error) {
    $("#log").text("Error: " + error.message);
});

Twilio.Device.connect(function (conn) {
    $("#log").text("Successfully established call");
});

/* Log a message when a call disconnects. */
Twilio.Device.disconnect(function (conn) {
    $("#log").text("Call ended");
});

/* Listen for incoming connections */
Twilio.Device.incoming(function (conn) {
  $("#log").text("Incoming connection from " + conn.parameters.From);
  // accept the incoming connection and start two-way audio
  conn.accept();
});

/* A function to end a connection to Twilio. */
function hangup() {
    Twilio.Device.disconnectAll();
}
</script>

<!-- use an onclick action to hang up the call when the user presses
the button -->
<button class="hangup" onclick="hangup();">
  Hangup
</button>
<div id="log"></div>

Next, we need to create a controller action that will render some TwiML instructing Twilio to connect any incoming calls to the client named jenny. There is a library called ExTwiml that provides a nice DSL for generating TwiML with Elixir. Add it as a dependency with {:ex_twiml, "~> 2.1.0"}.

Create the following controller action and module for rendering the TwiML

defmodule Demo.TwilioController do
  use Demo.Web, :controller

  def show(conn, _params) do
    token =
      ExTwilio.Capability.new
      |> ExTwilio.Capability.allow_client_incoming("jenny")
      |> ExTwilio.Capability.token

    render(conn, "show.html", token: token)
  end

  # Note: By default, Twilio will POST to this endpoint
  def voice(conn, _params) do
    resp = Demo.Twiml.dial_jenny
    conn
    |> put_resp_content_type("text/xml")
    |> text(resp)
  end
end

defmodule Demo.Twiml do
  import ExTwiml

  def dial_jenny do
    twiml do
      # This should be your Twilio Number or verified Caller ID
      dial callerid: "+1XXXXXXX" do
        client "jenny"
      end
    end
  end
end

Once you've started your web server, you can expose your endpoint to the world with a tool like Ngrok, pointing it to your development server on port 4000

$ ngrok http 4000

Create a TwiML application on Twilio, which will tell Twilio where to get instructions for routing incoming calls. Set the URL to point to your voice endpoint exposed by Ngrok, e.g.

http://xxxxxxxx.ngrok.io/voice Note: this URL will change every time you restart Ngrok

In order to test making an inbound call to your client, you can use the Call button visible on the Twilio console page for your TwiML application. Open the page corresponding to the show action in your browser. Then, on a different computer, click the Call button on the Twilio console - you should be able to carry on a conversation through your browsers.