Asterisk AGI not receiving DTMF digits after Background(), but CLI shows DTMF events

Asterisk Asterisk APIs
1

Hi everyone,

I’m facing an issue where DTMF digits are detected by Asterisk and visible in the CLI, but my AGI script is unable to receive them.

Environment

  • Asterisk 18.26.4-vici

  • AGI script written in Perl

  • Incoming SIP trunk call

Call Flow

  1. Answer call

  2. Play welcome message

  3. Play language selection menu

  4. Wait for caller to press a digit

Dialplan:

#!/usr/bin/perl

use strict;
use warnings;
use Asterisk::AGI;

my $agi = new Asterisk::AGI;

Play welcome

$agi->exec(‘Playback’, ‘SeylanPL/Ann01_Welcome’);

Play language prompt and wait for one digit

my $result = $agi->exec(‘Background’, ‘SeylanPL/Ann02_Lang’, 10000, 1);
my $digit = $result->{result} // ‘’;

$agi->verbose(“Digit pressed: [$digit]”, 1);

my $szLanguage = ‘’;

if ($digit eq ‘1’) {
$szLanguage = ‘ENG’;
}
elsif ($digit eq ‘2’) {
$szLanguage = ‘SIN’;
}
else {
$szLanguage = ‘No Input’;
}

$agi->verbose(“Language: $szLanguage”, 1);

Branch based on language

if ($szLanguage eq ‘ENG’) {
$agi->exec(‘Playback’, ‘SeylanPL/ENG/Seylan_MainMenu_old’);
}
elsif ($szLanguage eq ‘SIN’) {
$agi->exec(‘Playback’, ‘SeylanPL/SIN/Seylan_MainMenu_old’);
}
else {
$agi->exec(‘Playback’, ‘vm-goodbye’);
}

CLI Output

Language menu is played correctly:

root’
Connected to Asterisk 18.26.4-vici currently running on cx (pid = 14357)
[Jun 4 17:52:23] == Using SIP RTP CoS mark 5
[Jun 4 17:52:23] > 0x7f032803f540 – Strict RTP learning after remote address set to: 10.1.9.246:17060
[Jun 4 17:52:23] – Executing [27893000@trunkinbound:1] AGI(“SIP/Carrier_1-00000096”, “agi-DID_route.agi”) in new stack
[Jun 4 17:52:23] – Launched AGI Script /usr/share/asterisk/agi-bin/agi-DID_route.agi
[Jun 4 17:52:23] – <SIP/Carrier_1-00000096>AGI Script agi-DID_route.agi completed, returning 0
[Jun 4 17:52:23] – Executing [s@SeylanPL:1] Answer(“SIP/Carrier_1-00000096”, “”) in new stack
[Jun 4 17:52:23] > 0x7f032803f540 – Strict RTP switching to RTP target address 10.1.9.246:17060 as source
[Jun 4 17:52:23] – Executing [s@SeylanPL:2] AGI(“SIP/Carrier_1-00000096”, “agi-VDAD_inbound_calltime_check.agi,CALLMENU-----YES-----SeylanPL-------------------------NO-----YES”) in new stack
[Jun 4 17:52:23] – Launched AGI Script /usr/share/asterisk/agi-bin/agi-VDAD_inbound_calltime_check.agi
[Jun 4 17:52:23] – <SIP/Carrier_1-00000096> Playing ‘sip-silence.gsm’ (escape_digits=) (sample_offset 0) (language ‘en’)
[Jun 4 17:52:23] – <SIP/Carrier_1-00000096> Playing ‘sip-silence.gsm’ (escape_digits=) (sample_offset 0) (language ‘en’)
[Jun 4 17:52:23] – <SIP/Carrier_1-00000096>AGI Script agi-VDAD_inbound_calltime_check.agi completed, returning 0
[Jun 4 17:52:23] – Executing [s@SeylanPL:3] Set(“SIP/Carrier_1-00000096”, “INVCOUNT=0”) in new stack
[Jun 4 17:52:23] – Executing [s@SeylanPL:4] AGI(“SIP/Carrier_1-00000096”, “AGIseylanPL.agi”) in new stack
[Jun 4 17:52:23] – Launched AGI Script /usr/share/asterisk/agi-bin/AGIseylanPL.agi
[Jun 4 17:52:23] – AGI Script Executing Application: (Playback) Options: (SeylanPL/Ann01_Welcome)
[Jun 4 17:52:23] – <SIP/Carrier_1-00000096> Playing ‘SeylanPL/Ann01_Welcome.slin’ (language ‘en’)
[Jun 4 17:52:25] – AGI Script Executing Application: (Background) Options: (SeylanPL/Ann02_Lang)
[Jun 4 17:52:25] – <SIP/Carrier_1-00000096> Playing ‘SeylanPL/Ann02_Lang.slin’ (language ‘en’)
[Jun 4 17:52:28] > 0x7f032803f540 – Strict RTP learning complete - Locking on source address 10.1.9.246:17060
[Jun 4 17:52:30] DTMF[32625][C-00000097]: channel.c:4027 __ast_read: DTMF begin ‘2’ received on SIP/Carrier_1-00000096
[Jun 4 17:52:30] DTMF[32625][C-00000097]: channel.c:4031 __ast_read: DTMF begin ignored ‘2’ on SIP/Carrier_1-00000096
[Jun 4 17:52:30] DTMF[32625][C-00000097]: channel.c:3913 __ast_read: DTMF end ‘2’ received on SIP/Carrier_1-00000096, duration 80 ms
[Jun 4 17:52:30] DTMF[32625][C-00000097]: channel.c:4002 __ast_read: DTMF end passthrough ‘2’ on SIP/Carrier_1-00000096
[Jun 4 17:52:30] AGIseylanPL.agi: Digit pressed:
[Jun 4 17:52:30] AGIseylanPL.agi: Language: No Input
[Jun 4 17:52:30] – AGI Script Executing Application: (Playback) Options: (vm-goodbye)
[Jun 4 17:52:30] – <SIP/Carrier_1-00000096> Playing ‘vm-goodbye.gsm’ (language ‘en’)
[Jun 4 17:52:31] – <SIP/Carrier_1-00000096>AGI Script AGIseylanPL.agi completed, returning 0
[Jun 4 17:52:31] – Auto fallthrough, channel ‘SIP/Carrier_1-00000096’ status is ‘UNKNOWN’
[Jun 4 17:52:31] WARNING[32625][C-00000097]: func_hangupcause.c:138 hangupcause_read: Unable to find information for channel
[Jun 4 17:52:31] – Executing [h@SeylanPL:1] AGI(“SIP/Carrier_1-00000096”, “agi://127.0.0.1:4577/call_log–HVcauses–PRI-----NODEBUG-----0--------------------)”) in new stack
[Jun 4 17:52:31] WARNING[32625][C-00000097]: res_agi.c:2038 handle_connection: Connecting to ‘127.0.0.1:4577’ failed for url ‘agi://127.0.0.1:4577/call_log–HVcauses–PRI-----NODEBUG-----0--------------------)’: Connection refused
[Jun 4 17:52:31] WARNING[32625][C-00000097]: res_agi.c:2098 launch_netscript: Couldn’t connect to any host. FastAGI failed.
cx*CLI>

Question

Why is the DTMF visible in the Asterisk CLI but not available to the AGI script?

How fix this issue?

2

Background is meant for dialplan usage, and internally would handle DTMF. If you want access to the DTMF, you would instead use the actual AGI command instead[1].

[1] GET DATA - Asterisk Documentation

3

It has been my experience that using the AGI exec command to execute a dialplan application yields less control and fewer features than using the ‘native’ AGI command.

The only dialplan applications I’ve exec’d in over 20 years are dumpchan, monitor, and resetcdr.