Voicemail

Introduction

The Vonage Voice API is the easiest way to build high-quality voice applications in the Cloud. In this guide you will learn how to record audio from inbound calls using .NET and the Vonage Voice API.

This guide provides step by step instructions showing you how to:

1. Set up a Vonage account
2. Create a Vonage Application
3. Configure a Vonage Application
4. Create an ASP.NET Core application
5. Add the Vonage package to it
6. Receive a call and record it
7. Retrieve the recording from Vonage

Prerequisites

There are a few prerequisites that you need to complete before you can work through this guide. If you've already completed any of them, feel free to skip that step.

Create Vonage Account

You can create a Vonage account via the Dashboard. Within the Dashboard you can create Applications and purchase Vonage numbers. You can also perform these tasks using the Vonage CLI.

Install the Vonage CLI

The Vonage CLI allows you to carry out many operations on the command line. Examples include creating applications, purchasing numbers, and linking a number to an application.

To install the CLI with NPM run:

Set up the Vonage CLI to use your Vonage API Key and API Secret. You can get these from the settings page in the Dashboard.

Run the following command in a terminal, while replacing API_KEY and API_SECRET with your own:

How to run Ngrok

You must make your webhook accessible to Vonage’s APIs over the public Internet. A straightforward way to achieve this during development without standing up your own server is to use Ngrok. To learn more, read our documentation on Ngrok.

Download and install ngrok, then execute the following command to expose your application on port 3000 to the public Internet:

If you are a paid subscriber you could type:

Create a Voice Application

There are two methods for creating a Voice application:

1. Using the Vonage CLI
2. Using the Dashboard

Each of these methods is described in the following sections.

How to create a Voice application using the Vonage CLI

To create your application using the Vonage CLI, enter the following command into the shell replacing NGROK_HOST_NAME with the ngrok host that you got when you set up ngrok:

This command creates a Vonage Application with Voice capability. It configures the Application with your answer and event webhook URLs and generates a private key file private.key, which you should save in your project directory.

The command returns a unique Application ID. Use this Application ID to link your Vonage virtual number to your Application by executing the following:

This will link that Vonage Virtual Number to your application, which will cause all voice events occurring for that number to be routed to your designated URLs.

How to create a Voice application using the Dashboard

You can create Voice applications in the Dashboard.

To create your application using the Dashboard:

1. Under Applications in the Dashboard, click the Create a new application button.

2. Under Name, enter the Application name. Choose a name for ease of future reference.

3. Click the button Generate public and private key. This will create a public/private key pair and the private key will be downloaded by your browser. Save the private key that was generated.

4. Under Capabilities select the Voice button.

5. In the Answer URL box, enter the URL for your inbound calls webhook, for example, http://example.com/webhooks/answer.

6. In the Event URL box, enter the URL for your call status webhook, for example, http://example.com/webhooks/events.

7. Click the Generate new application button.

8. You are now taken to the next step of the Create Application procedure where you should link your Vonage number to the application.

You have now created your application.

Create the Voice Project File

To start, you will create a Voice csproj file. To make testing easier, configure Kestrel with HTTPS disabled.

In your terminal, execute the following command:

Install Vonage Package

To install the Vonage NuGet package, change directory into the VonageVoice repository and run the following command:

You can now open the VonageVoice.csproj file in Visual Studio.

Add Voice Controller

Right-click on the Controllers folder and select add->Controller. Select "Add Empty MVC Controller" and name it VoiceController.

Add using statements for Vonage.Voice, Vonage.Voice.Nccos, Vonage.Voice.Nccos.Endpoints, Vonage.Request, and Microsoft.Extensions.Configuration at the top of this file.

Inject Configuration

Dependency inject an IConfiguration object via the constructor:

Add Voicemail Answer Route

Add a route to your VoiceController to handle the inbound call. This will be located at /webhooks/answer and will return a NCCO with a record action, which instructs Vonage to start recording the call.

You must also specify the URL of another webhook - /webhooks/recording - which Vonage will make a request to when the recording is ready for download. You will code this webhook in the next step.

Add Recording Route

After the call has finished recording, Vonage will send a request to the webhook URL you configured in the record action in your NCCO. This request will contain the URL from which you can download the audio file.

In this guide, you'll use the GetRecording API to download the recording to your local machine:

Configure the ASP.NET App

Open your appsettings.json file and add the following two fields to it:

• APPLICATION_ID: Your Voice API Application's unique identifier.
• PRIVATE_KEY_PATH: The location of your Application's private.key file.

Run Your App

In your console navigate to the csproj directory and execute the command dotnet run --urls=http://localhost:3000. This will start the application up on http://localhost:3000. Open that URL in your browser.

What's Next?

Find out more about the capabilities of the Vonage Voice API:

• Read the Voice API documentation
• View the API Reference
• Play Text To Speech into a Call
• Play Audio into a Call
• Take Speech Input
• Handle User Key Input
• NCCO Reference