Telephony Service Development on Asterisk Platform

Hamid Fadishei
Assistant Professor, University of Bojnord
fadishei@yahoo.com http://www.fadishei.ir
Spring 2015
Telephony Service Development on Asterisk
Platform
Workshop

Hamid Fadishei
University of Bojnord Telephony Service Development on Asterisk Platform
What's Asterisk?
 Hard to tell in one sentence
 A very powerful, flexible, and extensible piece of integrated
telecommunications software
 An Open Source Telephony Swiss Army Knife
 A Linux Based PBX w/ Minimal Hardware Reqs
 A Community Driven Development Project
Asterisk turns an ordinary computer into a communications server. Asterisk powers
IP PBX systems, VoIP gateways, conference servers and is used by small
businesses, large businesses, call centers, carriers and governments worldwide.

Hamid Fadishei
Its birth
 Asterisk was created in 1999 by Mark Spencer
This guy!

Hamid Fadishei
Telecom technology, once upon a time...
 No switch

Hamid Fadishei
 Human switch!

Hamid Fadishei
 Mechanical switch

Hamid Fadishei
 Soft switch Digital switch

Hamid Fadishei
 Soft switch

Hamid Fadishei
Its capabilities
 Asterisk can do many cool things... It can be used as a...
 Legacy PBX Replacement
 Voicemail Server
 Conferencing Server
 Call Center ACD Queue
 VoIP Endpoint for IP Phones
 Calling Card Application
 Predictive Dialer
 Home Answering Machine
 …
In this workshop, we'll use it to implement a software-based IVR machine. At
the end of this workshop, we will hopefully implement a simple telephony
weather service

Hamid Fadishei
It's architecture
 Asterisk's power comes from its modular architecture
 Its core's functionality can be extended by loading additional
modules
Core
Module Module Module...
Techn.a Techn. b Techn.c...
Feature a Feature b Feature c

Hamid Fadishei
Core
SIPPhone
Analog
Phone
chan_sip chan_dahdi
IP PSTN
Google
Talk
chan_gtalk
IP

Hamid Fadishei
How to install Asterisk
 Different approaches
 Compile from source codes
 Obtain the source code from asterisk.org
 Compile and install it (make install)
 Install precompiled binaries
 Some Linux distributions offer Asterisk in their official repos
 Debian, Ubuntu, and Fedora
 Some offer it by third-party repos
 Centos (via EPEL), Arch (via AUR)
 Install an Asterisk-bundled operating system
 Such as AsteriskNow or Elastix
 The Choice is yours... but I would recommnd...
 The second approach
 less installation hassles, good understanding of the system internals
 takes advantage from regular OS updates
 I prefer packages from either Centos+EPEL or Debian

Hamid Fadishei
Experimental environment
 We will try asterisk in this environment
 Hardware
 A VM inside Virtualbox
 RAM: 1024MB, CPU:1, HDD: 8GB
 Operating Systems:
 Latest Debian stable release as of today which would be Debian
8.0.0 Jessie

Hamid Fadishei
Step 1 - Creating a VM
 Make sure hardware virtualization support is enabled in
your BIOS settings
 Install Virtualbox if you haven't already
 Also install the extension pack
 Create a new VM
 32-bit Debian Linux
 Name it astN where N is the number of your seat (mine is ast1)
 Select 1024MB of RAM and 8GB of HDD
 Configure its network in Bridge mode (because we need it to
be visible from the Lab LAN)

Hamid Fadishei
Step 2 - Install Debian
 We will install a minimal debian with no graphical
Desktop
 Insert CD#1 ISO image of Debian 8 inside the CD drive of your
new VM and start it
 Select the first boot menu option, "Install"
 Use guided partitioning
 Do not opt to use a network mirror
 Deselect Desktop Environment when it asks which features to
install
 Finally, you will get a login prompt
 Log in!
Debian GNU/Linux 8 ast1 tty1
ast1 login: _

Hamid Fadishei
Step 2 - Setup remote access to OS
 Working inside VM console is not easy enough
 We will setup an SSH server on our Debian system
 Then you can an SSH client such as Putty to access your
Debian command line remotely
 Now you should be able to SSH to your Debian using Putty
root@ast1:~# apt-get install openssh-server
...
root@ast1:~# nano /etc/ssh/sshd_config
PermitRootLogin yes
root@ast1:~# systemctl restart sshd

Hamid Fadishei
Step 3 - Install asterisk
 First,
 make sure that apt is configured to use debian repos
 Then,
 install asterisk
root@ast1:~# nano /etc/apt/sources.list
deb http://ftp.de.debian.org/debian jessie main contrib non-free
deb http://ftp.de.debian.org/debian/ jessie-updates main contrib non-free
deb http://security.debian.org/ jessie/updates main contrib non-free
root@ast1:~# apt-get update
root@ast1:~# apt-get install asterisk
...
:)

Hamid Fadishei
Asterisk CLI
 Asterisk comes with a command line interface (CLI)
 You can use it to manage and monitor your asterisk software
 Asterisk is configured via editin some conf files in
/etc/asterisk
 Next, we will setup some VoIP accounts
root@ast1:~# asterisk -r
Created by Mark Spencer <markster@digium.com>
Asterisk comes with ABSOLUTELY NO WARRANTY; type 'core show warranty' for details.
This is free software, with components licensed under the GNU General Public
License version 2 and other licenses; you are welcome to redistribute it under
certain conditions. Type 'core show license' for details.
=========================================================================
Connected to Asterisk 11.13.1~dfsg-2+b1 currently running on ast1 (pid = 3153)
ast1*CLI> _

Hamid Fadishei
Step4-AddacoupleofSIPaccounts
root@ast1:~# nano /etc/asterisk/sip.conf
[general]
allowguest=no
disallow=all
allow=gsm
jbenable=no
deny=0.0.0.0/0.0.0.0
permit=0.0.0.0/0.0.0.0
[101]
secret=asdf1234
context=phones
host=dynamic
type=friend
mailbox=101@default
callerid=Test 1 <101>
[102]
secret=asdf1234
context=phones
host=dynamic
type=friend
mailbox=102@default
callerid=Test 2 <102>

Hamid Fadishei
Step 4 - Adding SIP accounts...
 Now, tell asterisk to reload SIP configuration
 Install Zoiper on your host OS if you haven't already
 Configure it to user the 101 account on your Asterisk box
 Zoiper tells that the account is registerd, but...
 Calling any number will fail. why?
 Because no dial plan is configured on Asterisk
root@ast1:~# asterisk -r
ast1*CLI> sip reload
...
ast1*CLI> sip show peers
101...
201...
... 2 offline

Hamid Fadishei
Step 5 - Configuring a dial plan
 Add a simple dial plan
 And,...
 Then, dial 876
root@ast1:~# nano /etc/asterisk/extensions.conf
[general]
static=yes
writeprotect=no
autofallthrough=yes
[phones]
exten => 876,1,Answer()
exten => 876,2,Playback(hello-world)
exten => 876,3,Hangup()
ast1*CLI> dialplan reload

Hamid Fadishei
Dialplan structure
 Add a simple dial plan
root@ast1:~# nano /etc/asterisk/extensions.conf
[general]
static=yes
writeprotect=no
autofallthrough=yes
[phones]
exten => 876,2,Playback(hello-world)
exten => 876,3,Hangup()
Context
Extension
Priority
Application

Hamid Fadishei
Some hints
 You don't have to explicitly mentions priorities:
 You can use Goto application to write neater dialplans
[phones]
exten => 876,n,Playback(hello-world)
exten => 876,n,Hangup()
[phones]
exten => 876,1,Goto(hello,s,1)
[hello]
exten => s,1,Answer()
exten => s,n,Playback(hello-world)
exten => s,n,Hangup()

Hamid Fadishei
Calling phones
 In order to make a call to another phone registerd at
the same Asterisk server,
 You'll need to use the "Dial" application inside dialplan
...
[phones]
exten => 876,1,Goto(hello,s,1)
exten => 101,1,Dial(SIP/101)
exten => 102,1,Dial(SIP/102)
...

Hamid Fadishei
Power of Asterisk dialplan
 Asterisk allows you to write very complex dialplans
 But the focus of this workshop is not mastering dialplan
development
 We will focus on developing services using
programming languages such as Java or PHP

Hamid Fadishei
Asterisk Gateway Interface
 Asterisk can perform so many tasks by itself
 But sometimes we need to perform tasks
programmatically
 AGI is the solution!
 AGI and Asterisk servers can be on the same machine
 We'll use PHP language to develop our AGI applications
 But other languages (Java, C#, etc) could be used
Asterisk Server AGI Server
AGI Protocol

Hamid Fadishei
Step 6 - Install PHP Interpreter
 Simply install it from debian repo
 Test it really works
root@ast1:~# apt-get install php5-cli php5-curl
root@ast1:~# nano hello.php
<?php echo "hellon"; ?>
root@ast1:~# php ./hello.php
hello

Hamid Fadishei
Step 7 - AGI hello world
 Extract and copy PHPAGI library files:
 Create a simple AGI script:
 Configure dialplan to call the script
root@ast1:~# tar -xf phpagi-2.20.tgz
root@ast1:~# cp phpagi-2.20/phpagi*.php /usr/share/asterisk/agi-bin/
root@ast1:~# nano /usr/share/asterisk/agi-bin/hello.php
#!/usr/bin/php
<?php
set_time_limit(0);
require('phpagi.php');
$agi = new AGI();
$agi->answer();
$agi->stream_file('hello-world');
$agi->hangup();
?>
root@ast1:~# chmod a+x /usr/share/asterisk/agi-bin/hello.php
[phones]
exten => 875,1,AGI(hello.php)

Hamid Fadishei
Step 7 - AGI hello world
 Let's see PHP AGI class documentations
 answer()
 stream_file()
 hangup()

Hamid Fadishei
Step 8 - Developing the weather service
Internet

Hamid Fadishei
Step 8a - The welcome message
 Create another PHP AGI script named weather.php
 Upload the provided weather sounds folder to your
Asterisk server path /usr/share/asterisk/sounds
 Start with a simple welcome message on extension
874...
#!/usr/bin/php
<?php
set_time_limit(0);
require("phpagi.php");
$agi = new AGI();
$agi->answer();
$agi->stream_file("weather/welcome");

Hamid Fadishei
Step 8b - Getting the area code
 Let's see two more PHP AGI methods
 get_data()
 verbose()
...
$agi->stream_file("weather/welcome");
$data = $agi->get_data("weather/enter-area-code", 20000, 5);
$code = $data["result"];
$agi->verbose("got area code: $code");

Hamid Fadishei
Step 8c - Calculating the woeid
 Yahoo! weather webservice requires a region code
 We need to convert city area code to Yahoo! region
code
 A table can do the job
...
$agi->verbose("got area code: $code");
$woeids = array(
11 => 2255150, // Sari
13 => 2255086, // Rasht
17 => 2217763, // Gorgan
21 => 2251945, // Tehran
...
86 => 2254333, // Arak
87 => 2255130, // Sanandaj
);
$woeid = $woeids[$code];
$agi->verbose("got woeid: $woeid");

Hamid Fadishei
Step 8d -Always validate user input!
 Change this segment:
 to:
...
...
...
get_area_code;
...
if (!$woeid)
{
$agi->stream_file("weather/invalid-number");
goto get_area_code;
}

Hamid Fadishei
Step 8e - Calling the webservice
 Now we can call Yahoo! weather web service
 Start a music-on-hold before calling
$agi->stream_file("weather/wait");
$agi->set_music(true);
$base = "http://query.yahooapis.com/v1/public/yql";
$yql = "select item.condition from weather.forecast where woeid =
".$woeid." and u='c'";
$session = curl_init($base."?q=".urlencode($yql)."&format=json");
curl_setopt($session, CURLOPT_RETURNTRANSFER, true);
$json = curl_exec($session);
$weather = json_decode($json);
$temp = $weather->query->results->channel->item->condition->temp;
$agi->set_music(false);

Hamid Fadishei
Step 8f - Say temperature
 Finally, playback the temperature returned by Yahoo!
 Play it in sweet Persian!
if (!$temp || $temp<0 || $temp>99)
$agi->stream_file("weather/error");
else
{
$agi->verbose("got temperature: $temp");
$agi->stream_file("weather/temperature");
if ($temp >= 0 && $temp <= 19 || $temp % 10 == 0)
$agi->stream_file("weather/".$temp);
else
{
$d10 = (int)($temp/10)*10;
$d1 = $temp%10;
$agi->stream_file("weather/".$d10."-o");
$agi->stream_file("weather/".$d1);
}
$agi->stream_file("weather/degrees");
}
$agi->stream_file("weather/thanks");
$agi->hangup();

Hamid Fadishei
A few words on selecting hardware
 You don't have to use a PC for Asterisk SOHO
applications
 A low-cost small ARM board will do the task

Hamid Fadishei
Next steps
 Study other AGI operations
 Learn about FastAGI
 Learn about AMI (Asterisk Manager Interface)
 Master Asterisk configuration and dialplanning
 Develop FastAGI applications in Java
 Try FreeSwitch
(The Asterisk rival)
 Study Asterisk's
webservice interface
added in new releases

Telephony Service Development on Asterisk Platform

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