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Overview

When you don’t want to receive calls from a specific phone number or even a whole country, follow the instructions in this guide to create an application to block phone numbers or country codes associated with incoming calls.You can screen incoming calls either by using our PHLO visual workflow builder or our APIs and XML documents. Follow the instructions in one of the tabs below.
  • Using XML
Here’s how to use a Plivo XML document that screens incoming calls on a Plivo number.

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How it works

Inbound Call Flow
Plivo requests an answer URL when it answers the call (step 2) and expects the file at that address to hold a valid XML response from the application with instructions on how to handle the call. In this example, when an incoming call is received, we check whether the number has been blacklisted. If it has, we reject the call using the Hangup XML element. If the phone number hasn’t been blacklisted, we return a Speak XML element that says, “Hello, how are you today.”

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Prerequisites

To get started, you need a Plivo account — sign up with your work email address if you don’t have one already. You must have a voice-enabled Plivo phone number to receive incoming calls; you can rent numbers from the Numbers page of the Plivo console, or by using the Numbers API. If this is your first time using Plivo APIs, follow our instructions to set up a Node.js development environment and a web server and safely expose that server to the internet.

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Create an Express server to screen incoming calls

Create a file called screen_call.js and paste into it this code.
var plivo = require('plivo');
var express = require('express');
var bodyParser = require('body-parser');
var app = express();

app.use(bodyParser.urlencoded({extended: true}));
app.set('port', (process.env.PORT || 5000));

app.all('/screen_call/', function(request, response) {
    var blacklist = [ '<phone_number1>', '<phone_number2>', '<phone_number3>'];
    // Get the caller's phone number from the 'From' parameter
    var from_number = request.query.From || request.body.From;
    var r = plivo.Response();
    if (blacklist.indexOf(from_number) === -1){
        var body = "Hello, how are you today";
        r.addSpeak(body);
    } else {
        //Specify the reason for hangup

        var params = {'reason': "rejected"};
        r.addHangup(params);
    }
    console.log (r.toXML());
    response.set({'Content-Type': 'text/xml'});
    response.send(r.toXML());
});

app.listen(app.get('port'), function() {
    console.log('Node app is running on port', app.get('port'));
});
Replace the phone number placeholders with actual phone numbers (for example, 12025551234).

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Create a Plivo application to screen calls

Associate the Express server you created with Plivo by creating a Plivo application. Visit Voice > Applications in the Plivo console and click on Add New Application, or use Plivo’s Application API.Give your application a name — we called ours Screen Call. Enter the server URL you want to use (for example https://<yourdomain>.com/screen_call/) in the Answer URL field and set the method to POST. Click Create Application to save your application.
Create Screencall Application

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Assign a Plivo number to your application

Navigate to the Numbers page and select the phone number you want to use for this application.From the Application Type drop-down, select XML Application.From the Plivo Application drop-down, select Screen Call (the name we gave the application).Click Update Number to save.
Assign Screen call Application

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Test

Make a call to your Plivo number using any phone. Plivo will send a request to the answer URL you provided requesting an XML response and then process the call according to the instructions in the XML document the server provides. If your phone number is not blacklisted, the call will go through and you should hear, “Hello, how are you today.”