Technical Details

The Vonage Voice API is the easiest way to build high-quality voice applications in the Cloud. With the Voice API you can:

Build apps that scale with the web technologies you are already using
Control the flow of inbound and outbound calls in JSON with Nexmo Call Control Objects (NCCO). (Nexmo is now Vonage).
Record and store inbound or outbound calls
Create conference calls
Send text-to-speech messages in 40 languages with different genders and accents

In this document you can learn about:

How to Get Started with the Voice API, including examples in your language
References, API documentation and other supporting content
Further Reading, links to other useful content in the documentation

Getting Started

Voice Playground

In the Developer Dashboard, you can try out the Voice API interactively in the Voice Playground. Once you are signed up for a Vonage API account, you can go to Voice Playground in the Dashboard (Voice ‣ Voice Playground).

More details are available in this blog post: Meet Voice Playground, Your Testing Sandbox for Vonage Voice Apps

Using the API

The primary way that you'll interact with the Vonage API voice platform is via the public API. To place an outbound call, you make a POST request to https://api.nexmo.com/v1/calls.

To make this easier, Vonage provides Server SDKs in various languages that take care of authentication and creating the correct request body for you.

To get started, choose your language below and replace the following variables in the example code:

Key	Description
`VONAGE_NUMBER`	Your Vonage number that the call will be made from. For example `447700900000`.
`TO_NUMBER`	The number you would like to call to in E.164 format. For example `447700900001`.

Prerequisites

A Vonage application contains the required configuration for your project. You can create an application using the Vonage CLI (see below) or via the dashboard. To learn more about applications see our Vonage concepts guide.

Install the CLI

npm install -g nexmo-cli

Create an application

Once you have the CLI installed you can use it to create a Vonage application. Run the following command and make a note of the application ID that it returns. This is the value to use in NEXMO_APPLICATION_ID in the example below. It will also create private.key in the current directory which you will need in the Initialize your dependencies step

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

Execute the following command at your terminal prompt to create the JWT for authentication:

export JWT=$(nexmo jwt:generate $PATH_TO_PRIVATE_KEY application_id=$NEXMO_APPLICATION_ID)

Write the code

Add the following to make-an-outbound-call.sh:

curl -X POST https://api.nexmo.com/v1/calls\
  -H "Authorization: Bearer $JWT"\
  -H "Content-Type: application/json"\
  -d '{"to":[{"type": "phone","number": "'$TO_NUMBER'"}],
      "from": {"type": "phone","number": "'$VONAGE_NUMBER'"},
      "answer_url":["https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json"]}'

View full source

Run your code

Save this file to your machine and run it:

bash make-an-outbound-call.sh

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

npm install @vonage/server-sdk

Create a file named make-call.js and add the following code:

const { Vonage } = require('@vonage/server-sdk');

const vonage = new Vonage({
  applicationId: VONAGE_APPLICATION_ID,
  privateKey: VONAGE_APPLICATION_PRIVATE_KEY_PATH,
});

View full source

Write the code

Add the following to make-call.js:

vonage.voice.createOutboundCall({
  to: [
    {
      type: 'phone',
      number: TO_NUMBER,
    },
  ],
  from: {
    type: 'phone',
    number: VONAGE_NUMBER,
  },
  answer_url: [ANSWER_URL],
})
  .then((resp) => console.log(resp))
  .catch((error) => console.error(error));

View full source

Run your code

Save this file to your machine and run it:

node make-call.js

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

Add the following to build.gradle:

implementation 'com.vonage:server-sdk-kotlin:1.1.2'

Create a file named OutboundTextToSpeechCall and add the following code to the main method:

val client = Vonage {
    applicationId(VONAGE_APPLICATION_ID)
    privateKeyPath(VONAGE_APPLICATION_PRIVATE_KEY_PATH)
}

View full source

Write the code

Add the following to the main method of the OutboundTextToSpeechCall file:

val callEvent = client.voice.createCall {
    toPstn(TO_NUMBER)
    from(VONAGE_NUMBER)
    answerUrl(ANSWER_URL)
}

View full source

Run your code

We can use the application plugin for Gradle to simplify the running of our application. Update your build.gradle with the following:

apply plugin: 'application'
mainClassName = project.hasProperty('main') ? project.getProperty('main') : ''

Run the following gradle command to execute your application, replacing com.vonage.quickstart.kt.voice with the package containing OutboundTextToSpeechCall:

gradle run -Pmain=com.vonage.quickstart.kt.voice.OutboundTextToSpeechCall

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

Add the following to build.gradle:

implementation 'com.vonage:server-sdk:8.15.1'

Write the code

Add the following to the main method of the OutboundTextToSpeech file:

VonageClient client = VonageClient.builder()
        .applicationId(VONAGE_APPLICATION_ID)
        .privateKeyPath(VONAGE_PRIVATE_KEY_PATH)
        .build();

final String VONAGE_NUMBER = envVar("VONAGE_NUMBER");
final String TO_NUMBER = envVar("TO_NUMBER");
final String ANSWER_URL = "https://nexmo-community.github.io/ncco-examples/talk.json";

client.getVoiceClient().createCall(new Call(TO_NUMBER, VONAGE_NUMBER, ANSWER_URL));

View full source

Run your code

We can use the application plugin for Gradle to simplify the running of our application. Update your build.gradle with the following:

apply plugin: 'application'
mainClassName = project.hasProperty('main') ? project.getProperty('main') : ''

Run the following gradle command to execute your application, replacing com.vonage.quickstart.voice with the package containing OutboundTextToSpeech:

gradle run -Pmain=com.vonage.quickstart.voice.OutboundTextToSpeech

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

Install-Package Vonage

Write the code

Add the following to MakeOutboundCall.cs:

var creds = Credentials.FromAppIdAndPrivateKeyPath(vonageApplicationId, vonagePrivateKeyPath);
var client = new VonageClient(creds);

var answerUrl = "https://nexmo-community.github.io/ncco-examples/text-to-speech.json";
var toEndpoint = new PhoneEndpoint() { Number = toNumber };
var fromEndpoint = new PhoneEndpoint() { Number = vonageNumber };

var command = new CallCommand() { To = new Endpoint[] { toEndpoint }, From = fromEndpoint, AnswerUrl = new[] { answerUrl } };
var response = await client.VoiceClient.CreateCallAsync(command);

View full source

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

composer require vonage/client

Write the code

Add the following to text-to-speech-outbound.php:

require_once __DIR__ . '/../config.php';
require_once __DIR__ . '/../vendor/autoload.php';

// Building Blocks
// 1. Make a Phone Call
// 2. Play Text-to-Speech

$keypair = new \Vonage\Client\Credentials\Keypair(
    file_get_contents(VONAGE_APPLICATION_PRIVATE_KEY_PATH),
    VONAGE_APPLICATION_ID
);
$client = new \Vonage\Client($keypair);

$outboundCall = new \Vonage\Voice\OutboundCall(
    new \Vonage\Voice\Endpoint\Phone(TO_NUMBER),
    new \Vonage\Voice\Endpoint\Phone(VONAGE_NUMBER)
);
$outboundCall->setAnswerWebhook(
    new \Vonage\Voice\Webhook(
        'https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json',
        \Vonage\Voice\Webhook::METHOD_GET
    )
);
$response = $client->voice()->createOutboundCall($outboundCall);

var_dump($response);

View full source

Run your code

Save this file to your machine and run it:

php text-to-speech-outbound.php

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

pip install vonage

Write the code

Add the following to make-an-outbound-call.py:

client = vonage.Client(
    application_id=VONAGE_APPLICATION_ID,
    private_key=VONAGE_APPLICATION_PRIVATE_KEY_PATH,
)

response = client.voice.create_call({
  'to': [{'type': 'phone', 'number': TO_NUMBER}],
  'from': {'type': 'phone', 'number': FROM_NUMBER},
  'answer_url': ['https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json']
})

pprint(response)

View full source

Run your code

Save this file to your machine and run it:

python make-an-outbound-call.py

Prerequisites

Install the CLI

npm install -g nexmo-cli

Create an application

Vonage needs to connect to your local machine to access your answer_url. We recommend using ngrok to do this. Make sure to change demo.ngrok.io in the examples below to your own ngrok URL.

nexmo app:create "Outbound Call code snippet" https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json http://demo.ngrok.io/webhooks/events --keyfile private.key

gem install vonage

Write the code

Add the following to outbound_tts_call.rb:

client = Vonage::Client.new(
  api_key: VONAGE_API_KEY,
  api_secret: VONAGE_API_SECRET,
  application_id: VONAGE_APPLICATION_ID,
  private_key: File.read(VONAGE_APPLICATION_PRIVATE_KEY_PATH)
)

response = client.voice.create(
  to: [{
    type: 'phone',
    number: TO_NUMBER
  }],
  from: {
    type: 'phone',
    number: VONAGE_NUMBER
  },
  answer_url: [
    'https://raw.githubusercontent.com/nexmo-community/ncco-examples/gh-pages/text-to-speech.json'
  ]
)

puts response.inspect

View full source

Run your code

Save this file to your machine and run it:

ruby outbound_tts_call.rb

Technical Details

Contents

Getting Started

Voice Playground

Using the API

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

Prerequisites

Install the CLI

Create an application

Write the code

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

Prerequisites

Install the CLI

Create an application

Write the code

Run your code

References

Further Reading