Dial Status Reporting Using Go

Here’s how to use Plivo APIs and XML to send callback events for dial status reporting.

How it works

Plivo requests an answer URL when a Plivo number receives a call (step 2) and expects the file at that URL to be configured in the application assigned to the number to hold a valid XML response with instructions on how to handle the call. For outbound calls you specify an answer URL along with the make call API request, and for incoming calls the answer URL is specified in the Plivo application associated with the phone number.

In addition to requests to the answer URL, Plivo initiates HTTP requests to your application server throughout the course of a call based on specific XML elements and attributes in your answer XML document (step 5). Such requests are broadly classified into two categories:

Action URL requests: These requests are typically invoked at the end of an XML element’s execution, and the server expects XML instructions to carry forward the call in response to these requests. This happens, for example, when a caller provides Touch-Tone input during GetInput XML execution.

Callback URL requests: These requests serve as webhooks to pass the application server information about events through the course of an XML element’s execution, such as when a conference participant is muted or unmuted. These callback URL requests can be used for dial status reporting. No XML instructions are expected in response to these requests.

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

Create a Go application for dial status reporting

Create a file called dial_status.go and paste into it this code.

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package main

import (
	"github.com/go-martini/martini"
	"github.com/plivo/plivo-go/v7/xml"
	"net/http"
)

func main() {
	m := martini.Classic()
	m.Post("/dialstatus/", func(w http.ResponseWriter, r *http.Request) string {
		w.Header().Set("Content-Type", "application/xml")
		response := xml.ResponseElement{
			Contents: []interface{}{
				new(xml.DialElement).
					SetAction("https://<yourdomain>.com/dialstatus/action/").
					SetMethod("POST").
					SetRedirect(true).
					SetContents([]interface{}{
						new(xml.NumberElement).
							SetContents("<phone_number>"),
					}),
			},
		}
		return response.String()
	})
	m.Post("/dialstatus/action", func(w http.ResponseWriter, r *http.Request) string {
		status := r.FormValue("DialStatus")
		aleg := r.FormValue("DialALegUUID")
		bleg := r.FormValue("DialBLegUUID")
		result := status + " " + aleg + " " + bleg
		return result
	})
	m.Run()
}

Replace the phone number placeholder with an actual phone number in E.164 format (for example, +12025551234).

In this code, we tell Plivo to POST the call status to https://<yourdomain>.com/dialstatus/. We set the redirect attribute, which determines whether to change the call flow of an ongoing call based on the actions performed, to true, which tells Plivo to expect a valid XML document to be posted to https://<yourdomain>.com/dialstatus/action. The code creates an XML document with a Dial XML element.

Create a Plivo application for dial status reporting

Associate the Go application 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 Dial Status Report. Enter the server URL you want to use (for example https://<yourdomain>.com/dialstatus/) in the Answer URL field and set the method to POST. Click on Create Application to save your 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 Dial Status Report (the name we gave the application).

Click Update Number to save.

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, and call details will be posted to your application server via the action and callback URLs you configured throughout the course of the call.