[Freeswitch-users] How do I use eavesdrop?

18 Mar 2010

      I know eavesdrop is an application, not an API, so you have to use it 
differently.

I have an operator dialing in on extension 5000 being bridged to a 
client, and I'm getting those lovely little echoes that confirm the call 
is bridged (both operator and client softphones are sharing my one 
headset and mic.)

In the dialplan, I parse out the extension when someone dials in to 
665000 (last 4 digits are the extension to monitor), look up the 
appropriate operator UUID in my mnesia/Erlang tables, receive the "call" 
callback from Freeswitch, and build a proplists replacement with the 
execute-app-name set to "eavesdrop" and execute-app-arg set to the 
operator UUID.  I issue a sendmsg() command to Freeswitch, and it 
returns ok.

However, what happens to the extension that tried to eavesdrop is it 
gets two events: CHANNEL_PARK and SEND_MESSAGE.  The person making the 
eavesdrop call can't actually hear anything.

I've attached the Erlang callback module that the dialplan executes.  
The dialplan fragment is as follows:

<extension name=\"eavesdrop\">
    <condition field=\"destination_number\" 
expression=\"^66(\\d\\d\\d\\d)$\">
        <action application=\"answer\"/>
        <action application=\"set\" data=\"eavesdrop_extension=$1\" />
        <action application=\"erlang\" data=\"pbx_eavesdrop 
pursuit@testsrv\" />
    </condition>
</extension>

Unfortunately I can't think of any way to look up the UUID other than 
using the mnesia tables from the application.  When I tried the sample 
dialplans from Freeswitch, the eavesdrop module itself _did_ work.  I'm 
just having trouble cobbling together the "glue" for Erlang.

P.S. This is the last Freeswitch feature I have to code for this 
release, other than niggling cleanups like adding a few more voice 
prompts, which is easy enough as I've already sample code on how to do 
it.  With a little luck we'll make our April 1st ready-for-testing 
deadline!  We wouldn't have made it without Andrew's hints, tips, and 
tricks for using Erlang with Freeswitch. Thanks a lot! :D

-- 
Mark Sobkow
Senior Developer
MarkeTel Multi-Line Dialing Systems LTD.
428 Victoria Ave
Regina, SK S4N-0P6
Toll-Free: 800-289-8616-X533
Local: 306-359-6893-X533
Fax: 306-359-6879
Email: m.sobkow@marketelsystems.com
Web: http://www.marketelsystems.com 

%% Author: mark
%%
%% Created: Mar 8, 2010
%%
%% Description:
%%		This callback is executed when someone dials in to an eavesdrop
%%
-module(pbx_eavesdrop).

%%
%% Exported Functions
%%
-export([start/0, run/0, launch/1]).

%%
%% Include files
%%
-include_lib("figure/include/gut.hrl").
-include_lib("pbx/include/pbx_mnesia.hrl").

start() ->
	Pid = spawn( ?MODULE, run, [] ),
	register( ?MODULE, Pid ),
	syslog:debug( "pbx_eavesdrop:start() Started eavesdrop thread ~p~n", [Pid] ),
	{ ok, Pid }.

run() ->
	receive
		{ call, Data } ->
			{ event, [UUID | Rest]} = Data,
			EavesdropExtension = proplists:get_value( "variable_eavesdrop_extension", Rest ),
%%			syslog:debug( "pbx_eavesdrop:run() Rest=~p~n", [Rest] ),
			syslog:debug( "pbx_eavesdrop:run() New eavesdrop received for extension=~p~n", [EavesdropExtension] ),
			case pbx_mnesia:lookupOperatorByExtension( EavesdropExtension ) of
				{ ok, ExtensionRegistry } ->
					case proplists:is_defined( "execute-app-name", Rest ) of
						true ->
							PropsNoAppName = proplists:delete( "execute-app-name", Rest );
						_ ->
							PropsNoAppName = Rest
					end,
					case proplists:is_defined( "execute-app-arg", PropsNoAppName ) of
						true ->
							PropsNoAppArg = proplists:delete( "execute-app-arg", PropsNoAppName );
						_ ->
							PropsNoAppArg = PropsNoAppName
					end,
					PropsWithAppName = PropsNoAppArg ++
						[ proplists:property( "execute-app-name", "eavesdrop" ) ],
					PropsWithAppArg = PropsWithAppName ++
						[ proplists:property( "execute-app-arg",
							ExtensionRegistry#pbx_operator_registry.operator_uuid ) ],
%%					syslog:debug( "pbx_eavesdrop:run() sendmsg( ~p, ~p )~n", [ UUID, PropsWithAppArg ] ),
					EavesdropResult = pbx:sendmsg( UUID, PropsWithAppArg ),
					syslog:debug( "pbx_eavesdrop:run() EavesdropResult = ~p~n", [EavesdropResult] );
				Error ->
					%% Operator not logged in to extension
					syslog:info( "pbx_eavesdrop:run() Could not locate extension ~s, Error ~p~n", [ EavesdropExtension, Error ] ),
					_BgapiResult = pbx:bgapi( uuid_broadcast,
						UUID ++ " " ++ "/opt/freeswitch/sounds/en/us/callie/misc/8000/sorry.wav both" ),
					_ResultHangup = pbx:bgapi( sched_hangup, "+3 " ++ UUID )
			end,
			run();
		{call_event, Data} ->
			{ event, [UUID | Rest]} = Data,
			EventName = proplists:get_value( "Event-Name", Rest ),
			syslog:debug( "pbx_eavesdrop:run() call_event UUID=~p, EventName=~p~n", [UUID, EventName] ),
			run();
		{get_pid, _UUID, Ref, Pid} ->
			NewPid = spawn( ?MODULE, run, [] ),
			syslog:debug( "pbx_eavesdrop:run() Request to spawn new handler process, returning PID ~p~n", [NewPid] ),
			Pid ! { Ref, NewPid },
			run()
	end.

launch( Ref ) ->
	NewPid = spawn( ?MODULE, run, [] ),
	syslog:debug( "pbx_eavesdrop:launch() Returning new PID ~p~n", [NewPid] ),
	{Ref, NewPid}.