Receive Incoming Calls Using .NET

Overview

This guide shows how to receiving incoming calls on a Plivo number and greet callers with a text-to-speech message. Managing incoming calls is a key part of the call flow in many common use cases, such as interactive voice response (IVR), call forwarding, and conference calling.

You can handle 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.

You can create and deploy a PHLO to receive an inbound call with a few clicks on the PHLO canvas, without writing a single line of code.

How it works

When you receive a call on a voice-enabled Plivo number, you can control the call flow by associating a PHLO application to that Plivo number. Plivo will fetch the PHLO associated with the number and expect valid instructions via PHLO to handle the call.

Prerequisites

To get started, you need a Plivo account — sign up with your work email address if you don’t have one already. To receive incoming calls, you must have a voice-enabled Plivo phone number. You can rent numbers from the Numbers page of the Plivo console, or by using the Numbers API.

Create the PHLO

To create a PHLO, visit the PHLO page of the Plivo console. If this is your first PHLO, the PHLO page will be empty.

Create a PHLO to receive incoming call

  • Click Create New PHLO.
  • In the Choose your use case pop-up, click Build my own. The PHLO canvas will appear with the Start node.
    Note: The Start node is the starting point of any PHLO. It lets you trigger a PHLO to start upon one of three actions: incoming SMS message, incoming call, or API request.
  • From the list of components on the left side, drag and drop the Play Audio component onto the canvas. When a component is placed on the canvas it becomes a node.
  • Draw a line to connect the Start node’s Incoming Call trigger state to the Play Audio node.
  • In the Configuration pane at the right of the canvas, configure the Play Audio node to play a message to the caller.
  • Once you’ve configured the node, click Validate to save the configuration.
  • Give the PHLO a name by clicking in the upper left, then click Save.

Assign the PHLO to a Plivo number

Once you’ve created and configured your PHLO, assign it to a Plivo number.

  • On the Numbers page of the console, under Your Numbers, click the phone number you want to use for the PHLO.
  • In the Number Configuration box, select PHLO from the Application Type drop-down.
  • From the PHLO Name drop-down, select the PHLO you want to use with the number, then click Update Number.

Assign PHLO to a Plivo number

Test

You can now make a call to your Plivo phone number and see how the inbound call is handled.

For more information about creating a PHLO application, see the PHLO Getting Started guide. For information on components and their variables, see the PHLO Components Library.

Here’s how to use a Plivo XML document that handles incoming calls on a Plivo number by playing a text-to-speech message to the caller.

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, Plivo’s text-to-speech engine plays a message using the Speak XML element.

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 .NET development environment and a web server and safely expose that server to the internet.

Create an MVC controller to handle incoming calls

In Visual Studio, create a new project. Use the template for Web Application (Model-View-Controller).

Create an MVC app

Give the project a name — we used Receivecall.

Configure the MVC app

Navigate to the Controllers directory in the Receivecall project. Create a controller named ReceivecallController.cs and paste into it this code.

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using System;
using Plivo.XML;
using System.Collections.Generic;
using Microsoft.AspNetCore.Mvc;

namespace Receivecall
{
    public class ReceivecallController : Controller
    {
        public IActionResult Index()
        {
            Plivo.XML.Response resp = new Plivo.XML.Response();
            resp.AddSpeak("Hello, you just received your first call",
                new Dictionary<string, string>() {
        {
        "loop",
        "3"
        }
                });
            var output = resp.ToString();
            Console.WriteLine(output);

            return this.Content(output, "text/xml");
        }
    }
}

Create a Plivo application to receive calls

Associate the controller 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 Receive_call. Enter the server URL you want to use (for example https://<yourdomain>.com/receive_call/) in the Answer URL field and set the method to POST. Click Create Application to save your application.

Create Application

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 Receive_call (the name we gave the application).

Click Update Number to save.

Assign Phone Number to Receive Call App

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. You should hear the text-to-speech message, “Hello, you just received your first call.”