Asterisk on Rails:

Using RAGI to create voice applications

What is Ruby on Rails?

What is Ruby on Rails?

• Ruby – the programming language– 10 years old, originated in Japan– Interpreted, not statically typed, object-oriented– “more powerful than Perl, and more object-oriented than Python”

• Rails – the framework– A full-stack web framework written using the Ruby programming

language. Everything that you need to write a web application. – “web applications that formerly might have taken weeks or months

to develop can be produced in a matter of days.” - Tim O'Reilly

Rails

• “Convention over configuration”• “Don’t repeat yourself”• Features:

– Model-View-Controller– Simple database access via ActiveRecord– Integrated AJAX– Pretty URLs via routing– Flexible caching– Integrated testing framework– Integrated debugging

Sites that use Rails:http://www.basecamp.comhttp://www.43things.comhttp://www.odeo.comMany more

What is Asterisk?

“Asterisk is an Open Source PBX”

x101 = Amit

x102 = Sally

x103 = Arnaud• Internet

• Phone lines• Linux hardware

• Asterisk

• Optional: TDM card• Phones

• VoIP phones

• Softphones

• SIP

• IAX

• POTS

Call to (415)555-1212…

“Please enter the

extension…”

What could you use Asterisk to do?

• Set up an office with 4 phone lines, 25 extensions and 1 receptionist

• Make the best home phone system ever

• Build an IVR, call queuing and live customer support app for a banking call center

• Power voicemail for Vonage

• Call a list of phone numbers with a recorded message, “This is congressman Baird, did you know you can add yourself to the National Do Not Call list? Press 1 to add yourself now…”

Asterisk: The Apache of Telephony

• Asterisk is an open source bundle of telephony protocols and VoIP magic, in a PBX form factor.

• Features: extensions, voicemail, conferencing, IVR, 3-way calling, caller ID, speech to text (Sphinx), text to speech (Festival)

• Protocols: SIP, IAX, H.323, ADSI, +

• Extensibility: the dialplan, AGI, manager API, C API

Interfacing with Asterisk• There are several ways to write applications for

Asterisk out of the box– The dialplan - extensions.conf

• Hard to write and debug complicated systems, but fast.

– AGI (Asterisk Gateway Interface)• Asterisk calls out to an application during dialplan.• Run telephony and app processes on separate servers

– AMI (Asterisk Manager Interface)• Monitor asterisk call channel state

– Modify the source code / loadable module • Hey it is open source.• Changes will be need to be migrated each version.• C code, will run fast, extensive access to asterisk internals via APIs

RAGI = Rails + Asterisk

What is RAGI?

• RAGI = Ruby Asterisk Gateway Interface

• Asterisk AGI implementation in Ruby + more

• Supports both incoming and outgoing calls

• Adds a “Handler” class type to Rails apps for doing phone apps

Architecture

Ruby on Rails Asterisk

RAGI Server

Call Handleranswer();i = 0;n.times doendhangUp()

VoIP Protocol HandlingApplication Logic

databaseAGI

Why RAGI?

• You are using Rails and/or Ruby for other development.

• Asterisk alone is not enough: Wrestling with “extension.conf” is fine for PBX but not well suited for data-driven apps with complex flows

• Deployment: separate your app server from your telephony server

• Development: Direct access to your object hierarchy within your phone app

What could you use RAGI to do?

• Add a mobile interface to your web app that has more reach than with WAP or SMS

• Add a phone interface to your blog (posting + listening)

• Mash up RSS and IVR for a better kind of 411

• Route the call center calls to the CRM app (finally)

• Broadcast live audio from the game to people listening to streaming audio off a website

• Alternate reality games… the pay phone rings, a clue is given, punch in your cell phone number, etc

• Rentable Phone Numbers - Temporary phone numbers for use in classified ads

• Click-n-talk with others who are viewing this web page

• Learn Chinese; fill out your profile and we’ll match you with a qualified instructor in China connecting you over voip and handling payment...

Nice reach

VoIP/PSTN Service

Asterisk + RAGI + RoR

Mobile phones

Fixed line phones

VoIP Clients

SIP, IAX

SIP

, Jabber

Web Browsers

HTTP

Who is using it?

• Released 2.5 months ago

• Nearly 500 downloads times

• Emails and generally– “Thanks, now I have an excuse to learn Rails”

and– “Thanks, now I have an excuse to learn Asterisk”

e.g. Mobile Payments in Ghana

Mobile Payments in Ghana (2)

RAGI saved me a lot of time, especially with the sample application using such an easy to use API. Ruby on Rails (ActiveRecord, really) helped a lot to bootstrap a working model and I was able to tie the model and RAGI in to my application logic easily. I was new to Ruby, though I know quite a few languages, and I had to absorb Ruby, Rails, RAGI and Asterisk.

Short story is after something like a week and a half, we had come up with the version that you can listen to in the audio demonstrations of the system.

“

”http://www.corenett.com/

mailto:guido@sohne.net

Guido Sohne

Let’s Build an App Right Now

Note: See screencast on http://www.snapvine.com/code/ragi

“Dial-a-Package.com”

Track packages from web and phone

Web: Use the web to enter UPS tracking numbers

Phone: Dial in to hear delivery status

For visual people…

For visual people…

For visual people…

For visual people…

For visual people…

For visual people…

For visual people…

For visual people…

Components

• Ruby on Rails web & phone app UI

• MySQL data storage

• Asterisk telephony low level

• RAGI connect Rails and Asterisk

Outline of Steps

• 1) Create Rails Install

• 2) Create database instance

• 3) Build web app

• 4) Install RAGI

• 5) Build call handler

Write the call handler

1. User dials in

2. Authenticate by caller ID (or ask)

3. For each user delivery,• Fetch and parse info from the web• Use text to speech to read status

4. Hangup

Listen…

Summary

• Asterisk = open source PBX, VoIP and telephony protocols

• RAGI = build phone interactions in your Ruby and Rails apps

• More info:

http://www.snapvine.com/code/ragi

Today’s demo code and screencast will be posted online soon!

Learn More

Contact: joe@snapvine.com

RAGI, these slides, a new tutorial and other goodies:

http://www.snapvine.com/code/ragi

http://www.asterisk.org

http://www.voip-info.org/wiki/

Backup Slides

Example CallHandler API

• answer, hangup• play_sound, record_file• dial• play_tone (various)• send_DTMF• MeetMe conferencing• get_data – read user input• speak_text – text to speech• say_digits, say_number, say_time• get call status• execute arbitrary Asterisk server extension

Configure RAGI

Ruby on Rails Asterisk

RAGI Server

Call Handler

Phone call

answer();i = 0;n.times doendhangUp()

Configuration:

1 Tell Asterisk where your RAGI server is (agi)

2 Tell Rails how to boot up with RAGI

Your call handlers are found using URL, just like a web browser.

e.g. exten => 101,2,agi(agi://192.168.1.203/banking/check_balance)

Call Handler

Goes here when the call is answered

RAGI Classes

• CallHandler – subclass this for each IVR you create

• CallConnection – an API used by a call handler to operate on the call (e.g. play_sound, get_data, say_digits, etc)

• CallServer – a process in your Rails app that communicates with your Asterisk server

• CallInitiate – a class used to trigger outbound calls

VoIP Termination / Origination• Origination – creation of a call session from the PSTN to a VoIP network. Think of this as a

mobile device dialing a number, and that call session routing back through the mobile network, to that number (DID), which is routed over VoIP to your Asterisk server. Think of it as “dialing a phone number to reach your VoIP server”

• Termination – creating a call session from the VoIP network to the PSTN. This of this as your server calling out to a regular phone number (e.g. Skype Out). Traffic is routed to a termination service provider who then routes the VoIP to the closest point of presence, where they typically have a switch that hands of to a PSTN network (i.e. to make a local phone call)

• Providers – There are many providers of termination and origination. Many ISPs have entered the business, and there are plenty of resellers of Level3 and Global Crossing offering the service.

• Prices – termination is ~$0.01 per minute within the USA and origination (phone numbers) for a few dollars per month flat rate unlimited minutes. International rates vary.

• Setup – once you have found a provider, it is easy to configure asterisk to accept inbound phone calls (origination) and hand them to particular RAGI handlers by configuring asterisks’ basic config files. Outbound (termination) is similarly easy to configure so that you can use RAGI to place calls to phone numbers.

• More info - http://www.voip-info.org/wiki/view/VOIP+Service+Providers+B2B

RAGI – developer SDK

“RAGI alone is like the 5th thing that makes me think I should sincerely add Ruby to Python as my two default languages” – Kendall Clark, Managing Editor of XML.com

“Ruby Asterisk Gateway Interface serves as a bridge between Ruby on Rails and Asterisk - Pretty exciting stuff” - David Heinemeier Hansson, creator of Ruby on Rails

“This has the potential to be really interesting, because Asterisk+Rails should be about a decade more advanced then anything that the IVR people are used to seeing.” – scottstuff blog

• Over 500 downloads in the first 2.5 months!

Ruby Asterisk Gateway Interface http://www.snapvine.com/code/ragi