Librevox

An EventMachine-based Ruby library for interacting with the open source telephony platform FreeSWITCH.

Librevox eventually came to life during a major rewrite of Freeswitcher. Not everything would fit into the existing architecture, and I felt that a blank slate was needed. Librevox and Freeswitcher looks much alike on the outside, but Librevox tries to take a simpler approach on the inside.

Prerequisites

Librevox lets you interact with FreeSWITCH through mod_event_socket. You should know how the event socket works, and the differences between inbound and outbound event sockets before proceeding. The wiki page on mod_event_socket is a good place to start.

Librevox is Ruby 1.9-only.

Inbound listener

To create an inbound listener, you should subclass Librevox::Listener::Inbound and add custom behaviour to it. An inbound listener subscribes to all events from FreeSWITCH, and lets you react on events in two different ways:

1. By overiding on_event which gets called every time an event arrives.

2. By adding an event hook with event, which will get called every time an event with the specified name arrives.

The header and content of the event is accessible through event.

Below is an example of an inbound listener utilising all the aforementioned techniques:

require 'librevox'

class MyInbound < Librevox::Listener::Inbound
  # Events to listen for (default is ALL)
  events ['CHANNEL_EXECUTE', 'CUSTOM foo']

  # Filters to apply (optional)
  filter 'Caller-Context' => ['default', 'example'], 'Caller-Privacy-Hide-Name' => 'no'

  def on_event e
    puts "Got event: #{e.content[:event_name]}"
  end

  # You can add a hook for a certain event:
  event :channel_hangup do
    # It is instance_eval'ed, so you can use your instance methods etc:
    do_something
  end

  # If your hook block takes an argument, a Librevox::Response object for
  # the given event is passed on:
  event :channel_bridge do |e|
    ...
  end

  def do_something
    ...
  end
end

Outbound listener

You create an outbound listener by subclassing Librevox::Listener::Outbound.

Events

An outbound listener has the same event functionality as the inbound listener, but it only receives events related to that given session.

Dialplan

When a call is made and Freeswitch connects to the outbound event listener, session_initiated is called. This is where you set up your dialplan:

def session_initiated
  answer do
    set "some_var", "some value" do
      playback "path/to/file" do
        hangup
      end
    end
  end
end

All channel variables are available as a hash named session.

When using applications that expect a reply, such as play_and_get_digits, you have to use callbacks to read the value, as the function itself returns immediately due to the async nature of EventMachine:

def session_initiated
  answer do
    play_and_get_digits "enter-number.wav", "error.wav" do |digit|
      puts "User pressed #{digit}"
      playback "thanks-for-the-input.wav" do
        hangup
      end
    end
  end
end

You can also use the commands defined in Librevox::Command, which, to avoid namespace clashes, are accessed through the api object:

def session_initiated
  answer do
    api.status
  end
end

They can be used in conjunction with applications, and do also take a block, passing the response to an eventual block argument.

Starting listeners

To start a single listener, connection/listening on localhost on the default port is quite simple:

Librevox.start SomeListener

it takes an optional hash with arguments:

Librevox.start SomeListener, :host => "1.2.3.4", :port => "8087", :auth => "pwd"

Multiple listeners can be started at once by passing a block to Librevox.start:

Librevox.start do
  run SomeListener
  run OtherListener, :port => "8080"
end

Closing connection

After a session has finished, e.g. because the calling part hangs up, an outbound socket still has its connection to FreeSWITCH open, so we can get post- session events. Therefore it is important that you close the connection manually when you are done. Otherwise you will have 'hanging' sessions, cloggering up your system. This can safely be done with close_connection_after_writing, which will wait for all outgoing data to be send before closing the connection. It is aliased as done for convenience.

Unless you are doing something specific, closing the connection on CHANNEL_HANGUP is most likely sufficient:

class MyListener < Librevox::Listener::Outbound
  event :channel_hangup do
    done
  end
end

Configuration

By default Librevox uses the Logger class from the Ruby standard library. You can configure the path to the log file and the log level through Librevox.options:

Librevox.options[:log_file] = "my_log_file.log"
Librevox.options[:log_level] = Logger::DEBUG

Rotating logs

If you start Librevox with Librevox.start, the log file will be reopened if you send SIGHUP to the Librevox process. This makes it easy to rotate logs with the standard logrotate(1).

Using Librevox::CommandSocket

Librevox also ships with a CommandSocket class, which allows you to connect to the FreeSWITCH management console, from which you can originate calls, restart FreeSWITCH etc.

>> require "librevox/command_socket"
=> true

>> socket = Librevox::CommandSocket.new
=> #<Librevox::CommandSocket:0xb7a89104 @server=“127.0.0.1”,
    @socket=#<TCPSocket:0xb7a8908c>, @port=“8021”, @auth=“ClueCon”>

>> socket.originate('sofia/user/coltrane', :extension => "1234")
>> #<Librevox::Response:0x10179d388 @content="+OK de0ecbbe-e847...">

>> socket.status
>> > #<Librevox::Response:0x1016acac8 ...>

Further documentation

All applications and commands are documented in the code. You can run yardoc from the root of the source tree to generate YARD docs. Look under the Librevox::Commands and Librevox::Applications modules.

Extras

• Source: http://github.com/vangberg/librevox
• API docs: http://rdoc.info/projects/vangberg/librevox
• Mailing list: librevox@librelist.com
• IRC: #librevox @ irc.freenode.net

License

(c) 2009-2014 Harry Vangberg harry@vangberg.name (c) 2011-2014 Firmafon ApS info@firmafon.dk

Librevox was inspired by and uses code from Freeswitcher, which is distributed under the MIT license and (c) 2009 The Rubyists (Jayson Vaughn, Tj Vanderpoel, Michael Fellinger, Kevin Berry), Harry Vangberg, see LICENSE-Freeswitcher.

Librevox is distributed under the terms of the MIT license, see LICENSE.