Create a webhook server
When an inbound call is received, Vonage makes a request to a publicly accessible URL of your choice - we call this the answer_url
. You need to create a webhook server that is capable of receiving this request and returning an NCCO containing a connect
action that will forward the call to the PSTN phone number. You do this by extracting the destination number from the to
query parameter and returning it in your response.
New project
Create a new project directory in a destination of your choice and change into it:
mkdir app-to-app-js
cd app-to-app-js
Inside the folder, initialize a new Node.js project by running this command:
npm init -y
Add dependencies
Next, install the required dependencies:
npm install express localtunnel --save
Also, install the Client SDK - you will use this later, when building the client application:
npm install nexmo-client --save
Create the server file
Inside your project folder, create a file named server.js
and add the code as shown below - please make sure to replace SUBDOMAIN
with an actual value. The value used will become part of the URLs you will set as webhooks in the next step.
'use strict';
const subdomain = 'SUBDOMAIN';
const express = require('express')
const app = express();
app.use(express.json());
app.get('/voice/answer', (req, res) => {
console.log('NCCO request:');
console.log(` - caller: ${req.query.from}`);
console.log(` - callee: ${req.query.to}`);
console.log('---');
var ncco = [{"action": "talk", "text": "No destination user - hanging up"}];
var username = req.query.to;
if (username) {
ncco = [
{
"action": "talk",
"text": "Connecting you to " + username
},
{
"action": "connect",
"endpoint": [
{
"type": "app",
"user": username
}
]
}
]
}
res.json(ncco);
});
app.all('/voice/event', (req, res) => {
console.log('EVENT:');
console.dir(req.body);
console.log('---');
res.sendStatus(200);
});
if(subdomain == "SUBDOMAIN") {
console.log('\n\t🚨🚨🚨 Please change the SUBDOMAIN value');
return false;
}
app.listen(3000);
const localtunnel = require('localtunnel');
(async () => {
const tunnel = await localtunnel({
subdomain: subdomain,
port: 3000
});
console.log(`App available at: ${tunnel.url}`);
})();
NOTE: Please remember to replace SUBDOMAIN
with a random string of your choice, containing letters, numbers, underscores or dashes.
There are 2 parts in the server code above:
The Express server
The first part creates an Express
server and makes it available locally on port 3000
. The server exposes 2 paths:
-
/voice/answer
is theanswer_url
we mentioned above. It sends back aJSON
response containing the destination number for the call.Notice, that the
number
is extracted from thereq.query.to
parameter that Vonage is sending as part of the request. The dynamically built NCCO then forwards the call to the destination phone using aconnect
action. The second one,
/voice/event
, you will set as destination for Vonage to notify you of everything happening during the call - we call this theevent_url
.
The localtunnel
integration
The second part of the server code above, exposes the Express
server so it will be accessible by the Vonage servers.
NOTE: localtunnel
is a JavaScript library that exposes your localhost to the world for painless testing and sharing! No need to mess with DNS or deploy to have others test out your changes.
Start the server
You can now start the server by running, in the terminal, the following command:
node server.js
A notice will be displayed telling you the server is now available:
App available at: https://SUBDOMAIN.loca.lt
Please keep the terminal window handy as you will need the URL in the next step.
Making an app to app voice call
You make a phone call from a web app to another web app.Steps