Reply to Incoming SMS Messages Using Ruby


This guide shows how to receive SMS text messages on a Plivo phone number — something you might want to do to acknowledge a request from a customer, handle opt-ins and opt-outs, or implement an autoresponder application.

You can reply to SMS messages either by using our PHLO visual workflow builder or our APIs. Follow the instructions in one of the tabs below.

You can create and deploy a PHLO to reply to an incoming text message with a few clicks on the PHLO canvas.


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 messages, you must have a Plivo phone number that supports SMS. 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.

  • 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-hand side, drag and drop the Send Message 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 Message trigger state to the Send Message node.

  • In the Configuration pane at the right of the canvas, configure the Send Message node with a sender ID in the From field. Enter as the To number the number from which you received the message that triggered the reply. Put your message in the Message field.

  • Once you’ve configured the node, click Validate to save the configuration.

  • After you complete 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


You can now send a message to your Plivo phone number and see that a reply is generated.

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 Plivo APIs to reply to incoming SMS text messages.


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 messages, you must have a Plivo phone number that supports SMS; 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 Ruby development environment and a web server and safely expose that server to the internet.

Create a Rails controller to reply to messages

Change to the project directory and run this command to create a Rails controller to reply to incoming messages.

$ rails generate controller Plivo sms

This command generates a controller named plivo_controller in the app/controllers/ directory and a respective view in app/views/plivo. We can delete the view as we don’t need it.

$ rm app/views/plivo/sms.html.erb

Edit app/controllers/plivo_controller.rb and paste this code in the PlivoController class.

include Plivo
include Plivo::Exceptions
include Plivo::XML

class PlivoController < ApplicationController
  skip_before_action :verify_authenticity_token
def replysms
	from_number = params[:From]
	to_number = params[:To]
	text = params[:Text]
	response =
	params = {
		src: to_number,
		dst: from_number,
	message_body = "Thank you, we received your request"
	response.addMessage(message_body, params)
	xml =
	puts xml.to_xml
	render xml: xml.to_xml

Add a route

Edit config/routes.rb and change the line

Rails.application.routes.draw do
  get 'plivo/sms' 


Rails.application.routes.draw do
  post 'plivo/replysms/' => 'plivo#replysms'

Start the Rails server

$ rails server

You should see your basic server application in action at http://localhost:3000/plivo/autoresponder/.

Set up ngrok to expose your local server to the internet.

Note: For ngrok testing, add this line to config/environments/development.rb.
config.hosts << /[a-z0-9-]+\.ngrok\.io/

Create a Plivo application to reply to messages

Associate the Rails controller you created with Plivo by creating a Plivo application. Visiting Messaging > Applications and click Add New Application. You can also use Plivo’s Application API.

Give your application a name — we called ours Reply Incoming SMS. Enter the server URL you want to use (for example https://<yourdomain>.com/replysms/) in the Message 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 Reply Incoming SMS (the name we gave the application).

Click Update Number to save.

Assign Phone Number to Reply SMS App


Send a text message to the Plivo number you specified using any phone. You should receive a reply.