Add a Call Whisper using Node and the Nexmo Voice API

This app used the Nexmo Voice APIs to demonstrate how add a "whisper" (a spoken announcement to only one caller before connecting) to a call using the onAnswer feature.

Prerequisites

You will need:

• A free Nexmo account
• The Nexmo CLI installed
• A way to run a local server on a public port, for example Ngrok.

Installation

git clone https://github.com/nexmo/node-call-whisper.git
cd node-call-whispher
npm install

Setup

Buy Numbers & Create Application

To run this application we need to buy 2 numbers, set up an application, and tie the numbers to this application.

# create an application
> nexmo app:create "Whisper System" http://your.domain/answer_inbound http://your.domain/event --type voice --keyfile app.key
# check the application ID
> nexmo app:list
12345678-1234-1234-1234-1234567890 | Whisper System
# purchase 2 numbers
> nexmo number:buy 4420 -c GB  --confirm
Number purchased: 442055555555
> nexmo number:buy 4420 -c GB  --confirm
Number purchased: 442055555556
# link the numbers to the application ID
> nexmo link:app 442055555555 12345678-1234-1234-1234-1234567890
> nexmo link:app 442055555556 12345678-1234-1234-1234-1234567890

Run Server

The next step is to set up all of our variables in a .env file. You can start off by copying the example file.

mv .env.example .env

Fill in the values in .env as appropriate, where INBOUND_NUMBER_1 and INBOUND_NUMBER_2 are the numbers you just purchased, CALL_CENTER_NUMBER is the number you want them to direct to, and NEXMO_APP_FILE_NAME is the file name of your application key (app.key). Finally, DOMAIN is the public domain or hostname your server is available on.

With this in place you can start the server.

npm start

The application should be available on http://localhost:5000. For this to work full though, make sure to expose your server on a public domain (e.g. your.domain in the example above) using a tool like Ngrok.

Using the App

To use the app you need two phones, or a phone and something like Skype to make the first call.

With your server running, call either of the 2 numbers you purchased. Nexmo will then make a call to http://your.domain/answer_inbound which puts the inbound call on hold. A call is then made to the CALL_CENTER_NUMBER(your other phone) where a message is played regarding the nature of the call before both parties are connected to the same conference.

More Information

For a more detailed writeup, see the tutorial on the Nexmo Developer Portal.