voicemail-notifier

A simple application to text me when Twilio records a voicemail on my behalf. I use this application on a phone number that had to be made public as a way for spammers and auto-dialers to not interrupt my workday, but to still be able to receive any important or legal messages that might be left for me.

Twilio's runtime platform handles most of the heavy lifting. This application just ensures that I'm notified by SMS when new voicemails are recorded by directing Twilio to text me when that happens.

Using

Deploying the application

First, you'll need a Twilio account. Once you get it, you'll need to purchase a phone number that can receive calls and send you SMS messages. Then you can proceed with setup. (direct link to phone number management)

This is distributed as a Docker image if you'd like to use it for yourself. You can find it at: farmdawgnation/voicemail-notifier on Docker Hub.

You will need to provide the following environment variables for it to work:

• ACCOUNT_SID - Account SID for your account
• AUTH_TOKEN or AUTH_TOKEN_FILE - Auth token for your account. If the file variant is defined the auth token will be read from a file, which is useful if you're mounting a secret into the file system.
• SOURCE_NUMBER - A phone number to send from. This will be the number you purchased on your Twilio account. This should be formatted as "+11234567890" for US numbers.
• TARGET_NUMBER - The phone number to send the notification to. This will be a real phone number that you use. This should be formatted as "+11234567890" for US numbers.
• VALIDATION_ENABLED - Set this to "true" to enforce Twilio request validation. Any incoming requests from Twilio are signed and turning this on will enforce checking those signatures. I highly recommend that you turn this setting on.
• BASE_URL - The Base URL that Twilio will use to contact your server including the http / https prefix. (e.g. http://domain.to.your.notifier)

Once you've got your docker container deployed, you should be able to send requests to it, but you'll likely get HTTP 401 responses unless you disabled validation. Once it's up and running you can configure Twilio's end.

Configuring Twilio

Once your app is up and running, you need to tell Twilio what to do with your number. You'll do this in the "Runtime" section of your Twilio account under "TwiML Bins" (direct link). You will specifically need to define:

• A TwiML bin to prompt the caller to record a message
• A TwiML bin to end the call once the caller finishes

Here are the examples I use:

Hangup (used after voicemail is recorded):

<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Hangup></Hangup>
</Response>

Record a 30 second call

<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Say voice="alice">Record your message at the beep</Say>
  <Record action="URL_TO_YOUR_HANGUP_BIN"
          recordingStatusCallback="URL_TO_YOUR_NOTIFY_DEPLOYMENT"
          timeout="10"
          transcribe="false"
          maxLength="30" />
  <Hangup />
</Response>

In the record call bin, replace URL_TO_YOUR_HANGUP_BIN with the URL Twilio generates for your Hangup bin (starts with https://handler.twilio.com/twiml/), and then replace URL_TO_YOUR_NOTIFY_DEPLOYMENT to the URL Twilio should hit to your notifier service. This should be http://domain.to.your.notifier/notify or something equivalent and it must match your BASE_URL or Twilio request validation will fail.

After you've created these bins, return to your phone management screen and click on the phone number you purchased for this voicemail service.

Under the voice and fax section ensure the following settings are selected:

• Accept Incoming: Voice Calls
• Configure with: Webhooks, TwiML Bins, Functions, Studio, or Proxy
• A Call Comes In: (name of your record message bin)

Save your changes.

That should be it. If things are working you should now be able to call your phone number, record a message, and get an SMS that you have a voicemail to listen to with a direct link to it.

You can also list and listen to the recordings in your Twilio Console. (direct link).

Development

Prerequisites

You will need Leiningen 2.0.0 or above installed.

Running

To start a web server for the application, run:

lein ring server-headless

License

Copyright © 2018 Matt Farmer. Licensed under the terms of the Apache 2.0 license.