8.1. A fax server with IAXmodem and Hylafax

The IAXmodem application emulates a faxmodem, which may be operated by a fax application of the administrator's choosing. We'll use the popular Hylafax. For simplicity and consistency, the installation platform will be the same Debian Linux and Asterisk 1.4 we have used for the other examples (see Section A.1, “Installing Asterisk 1.4.x on Debian Linux 4.0 (Etch)”).

Installing IAXmodem

IAXmodem simulates a faxmodem and makes it available to Asterisk via IAX2. All the steps in this chapter must be performed as the root user.
To install IAXmodem, we need some additional Debian packages, which may be installed with the command apt-get -y install g++ libtiff-tools libtiff4 libtiff4-dev.
debian:~# apt-get -y install g++ libtiff-tools libtiff4 libtiff4-dev
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut... Fertig
Die folgenden zusätzlichen Pakete werden installiert:
  g++ libjpeg62 libjpeg62-dev libtiffxx0 zlib1g-dev


Richte zlib1g-dev ein (1.2.2-4.sarge.2) ...
Richte libtiff4-dev ein (3.7.2-7) ...

We switch into the appropriate directory with cd /usr/src to install the IAXmodem source code:
debian:~# cd /usr/src
The sources for IAXmodem can be downloaded with any typical web browser from http://iaxmodem.sourceforge.net (the version used in this example is 0.3.0). After downloading the archive, copy it to /usr/src and unpack it with tar -xvzf iaxmodem-0.3.0.tar.gz.
debian:/usr/src# tar -xvzf iaxmodem-0.3.0.tar.gz 


Change into the unpacked directory with cd iaxmodem-0.3.0:
debian:/usr/src# cd iaxmodem-0.3.0
Now compile the sources with ./configure && make:
debian:/usr/src/iaxmodem-0.3.0# ./configure && make
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for gawk... no
checking for mawk... mawk
checking whether make sets $(MAKE)... yes
checking for gcc... gcc


cc -DMODEMVER=\"0.3.0\" -DDSPVER=\"spandsp-0.0.3-snapshot-20070223+\" -DIAXVER=\"libiax2-0.2.3-CVS-20060222+\" -Wall -g -DSTATICLIBS -DUSE_UNIX98_PTY -std=c99 -Ilib/libiax2/src -Ilib/spandsp/src  -c iaxmodem.c
cc -DMODEMVER=\"0.3.0\" -DDSPVER=\"spandsp-0.0.3-snapshot-20070223+\" -DIAXVER=\"libiax2-0.2.3-CVS-20060222+\" -Wall -g -DSTATICLIBS -DUSE_UNIX98_PTY -std=c99 -Ilib/libiax2/src -Ilib/spandsp/src  iaxmodem.o lib/spandsp/src/.libs/libspandsp.a lib/libiax2/src/.libs/libiax.a -o iaxmodem -lm -lutil -ltiff


Copy the resulting binary into /usr/bin with cp iaxmodem /usr/bin/:
debian:/usr/src/iaxmodem-0.3.0# cp iaxmodem /usr/bin/
Now we can configure the modem. IAXmodem expects to find configuration files in /etc/iaxmodem. Create it with mkdir /etc/iaxmodem:
debian:/usr/src/iaxmodem-0.3.0# mkdir /etc/iaxmodem
Create the configuration file with touch /etc/iaxmodem/ttyIAX0:
debian:/usr/src/iaxmodem-0.3.0# touch /etc/iaxmodem/ttyIAX0
This file must contain the following parameters:
The device node to be created in /dev. This is the device Hylafax uses to connect to IAXmodem. You can choose any name you like, but we prefer to adhere to the convention and so choose a device name appropriate for a serial interface, ttyIAX0.
This is the owner of the device (in the form user:group). It is best to use the same user and group under which Hylafax runs.
The port that IAXmodem listens on. Asterisk uses 4569 to listen for IAX2 connections, so you must choose something else, e.g. 4570.
This sets how long IAXmodem waits between registrations with Asterisk. If this number is 0, the modem does not register at all.
IP address of the server running Asterisk. If this is on the same machine as IAXmodem, use the localhost address
The name under which IAXmodem registers with Asterisk.
The password used for Asterisk registration.
The codec used by IAXmodem. Allowed codecs are alaw, ulaw and slinear. Compressed codecs are not appropriate for faxing; fax transmissions are themselves compressed and don't tolerate further compression; moreover, most compressed codecs are lossy and a fax transmission will not tolerate losses. This is one of the major reasons why faxing over VoIP remains problematic.
Using an appropriate editor (e.g. vi) we write the following configuration in the file /etc/iaxmodem/ttyIAX0:
device          /dev/ttyIAX0
owner           uucp:uucp
mode            660
port            4570
refresh         50
peername        iaxmodem
secret          password
codec           alaw
IAXmodem is now configured and can be started. The best way to do this is with init. Add a line to start IAXmodem to /etc/inittab with echo "IA00:23:respawn:/usr/bin/iaxmodem ttyIAX0" >> /etc/inittab:
debian:/usr/src/iaxmodem-0.3.0# echo "IA00:23:respawn:/usr/bin/iaxmodem ttyIAX0" >> /etc/inittab 
The device name ttyIAX0 is the same device name as specified in /etc/iaxmodem.
To receive faxes, we need a getty that listens for connections on the IAXmodem. This is accomplished through an additional entry in /etc/inittab. Add it with echo "mo00:23:respawn:/usr/sbin/faxgetty ttyIAX0" >> /etc/inittab.
mo00:23:respawn:/usr/local/sbin/faxgetty ttyIAX0
Create a log directory for IAXmodem with mkdir /var/log/iaxmodem/ and the log files with touch /var/log/iaxmodem/ttyIAX0 and touch /var/log/iaxmodem/iaxmodem.
debian:/usr/src/iaxmodem-0.3.0# mkdir /var/log/iaxmodem/
debian:/usr/src/iaxmodem-0.3.0# touch /var/log/iaxmodem/ttyIAX0
debian:/usr/src/iaxmodem-0.3.0# touch /var/log/iaxmodem/iaxmodem 
To make sure everything will start as expected at boot time, reboot the system with shutdown -r now.
debian:/usr/src/iaxmodem-0.3.0# shutdown -r now

Broadcast message from root@debian (pts/1) (Sat May  5 00:15:49 2007):

The system is going down for reboot NOW!

Installing Hylafax

We'll install Hylafax from the Debian Repository to simplify installation. Do this with apt-get -y install hylafax-server . Dependencies are automatically resolved:
debian:~# apt-get install -y hylafax-server
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut... Fertig
Die folgenden zusätzlichen Pakete werden installiert:
  enscript gs-common gs-esp hylafax-client libcupsimage2 libcupsys2 mailx metamail psmisc
Vorgeschlagene Pakete:
  gv postscript-viewer lpr gs-pdfencrypt gs-cjk-resource mgetty-viewfax hylafax-doc mgetty cupsys-common
Empfohlene Pakete:
  psfontmgr netpbm transfig
Die folgenden NEUEN Pakete werden installiert:
  enscript gs-common gs-esp hylafax-client hylafax-server libcupsimage2 libcupsys2 mailx metamail psmisc


Update /var/spool/hylafax/status/any.info.

        HylaFAX configuration parameters are:

        [1] Init script starts faxq:            yes
        [2] Init script starts hfaxd            yes
        [3] Start old protocol:                 no
        [4] Start paging protocol:              no
Are these ok [yes]? 
Modem support functions written to /var/spool/hylafax/etc/setup.modem.
Configuration parameters written to /var/spool/hylafax/etc/setup.cache.

Restarting HylaFAX server processes.

Should I restart the HylaFAX server processes [yes]? 
You do not appear to have any modems configured for use.  Modems are
configured for use with HylaFAX with the faxaddmodem(8) command.
Do you want to run faxaddmodem to configure a modem [yes]? 
Done verifying system setup.
Updating /etc/hylafax/setup.cache from /var/spool/hylafax/etc/setup.cache.
Updating /etc/hylafax/setup.modem from /var/spool/hylafax/etc/setup.modem.apt-get -y install hylafax-server
Starting HylaFAX: faxq hfaxd faxgetty.

The next step is the configuration of the fax server. Do this with faxsetup:
debian:/usr/src/hylafax-4.3.4# faxsetup


Update /var/spool/hylafax/status/any.info.

        HylaFAX configuration parameters are:

        [1] Init script starts faxq:            yes
        [2] Init script starts hfaxd            yes
        [3] Start old protocol:                 no
        [4] Start paging protocol:              no

Are these ok [yes]?
Simply press Enter after the following 2-3 questions.
You have a HylaFAX scheduler process running.  faxq will be
restarted shortly, as soon as some other work has been completed.
Can I terminate this faxq process (4048) [yes]?
Should I restart the HylaFAX server processes [yes]?

/etc/init.d/hylafax start
Not starting HylaFAX daemons since they are already running.


Modems are configured for use with HylaFAX with the faxaddmodem(8) command.
Do you want to run faxaddmodem to configure a modem [yes]? 
We confirm restart of the server processes with yes and are asked if we want to install a modem. Our IAXmodem is already set up so we can proceed and confirm again with yes.
Specify the modem and confirm with Enter.
Serial port that modem is connected to [ttyS0]? ttyIAX0

Ok, time to setup a configuration file for the modem.  The manual
page config(5) may be useful during this process.  Also be aware
that at any time you can safely interrupt this procedure.

Reading scheduler config file /var/spool/hylafax/etc/config.
Many questions follow, but only a few of them are really important.[56]This is where you set international dialing codes, the fax number, country and area code, and the CSID (Call Subscriber ID) which is printed on the top line of the fax page on the receiver's end. Confirm with yes.
No existing configuration, let's do this from scratch.

Country code [1]? 1
Area code []? 403
Phone number of fax modem [+1.999.555.1212]? +1 888 555 4091
Local identification string (for TSI/CIG) ["NothingSetup"]? 
Long distance dialing prefix [1]? 1
International dialing prefix [011]? 011
Dial string rules file (relative to /var/spool/hylafax) [etc/dialrules]? 
Tracing during normal server operation [1]? 
Tracing during send and receive sessions [11]? 
Protection mode for received facsimile [0600]? 
Protection mode for session logs [0600]? 
Protection mode for ttyIAX0 [0600]? 
Rings to wait before answering [1]? 
Modem speaker volume [off]? 
Command line arguments to getty program ["-h %l dx_%s"]? 
Pathname of TSI access control list file (relative to /var/spool/hylafax) [""]? 
Pathname of Caller-ID access control list file (relative to /var/spool/hylafax) [""]? 
Tag line font file (relative to /var/spool/hylafax) [etc/lutRS18.pcf]? 
Tag line format string ["From %%l|%c|Page %%P of %%T"]? 
Time before purging a stale UUCP lock file (secs) [30]? 
Hold UUCP lockfile during inbound data calls [Yes]? 
Hold UUCP lockfile during inbound voice calls [Yes]? 
Percent good lines to accept during copy quality checking [95]? 
Max consecutive bad lines to accept during copy quality checking [5]? 
Max number of pages to accept in a received facsimile [25]? 
Syslog facility name for ServerTracing messages [daemon]?
Set UID to 0 to manipulate CLOCAL [""]? 
Use available priority job scheduling mechanism [""]?
A confirmation page follows where you can double-check your entries:
The non-default server configuration parameters are:

CountryCode:            1
AreaCode:               403
FAXNumber:              +1 888 555 4091
LongDistancePrefix:     0
InternationalPrefix:    00
DialStringRules:        etc/dialrules
SessionTracing:         11
RingsBeforeAnswer:      1
SpeakerVolume:          off
GettyArgs:              "-h %l dx_%s"
LocalIdentifier:        "NothingSetup"
TagLineFont:            etc/lutRS18.pcf
TagLineFormat:          "From %%l|%c|Page %%P of %%T"
MaxRecvPages:           25

Are these ok [yes]?
Answering yes brings us to modem detection:
Now we are going to probe the tty port to figure out the type
of modem that is attached.  This takes a few seconds, so be patient.
Note that if you do not have the modem cabled to the port, or the
modem is turned off, this may hang (just go and cable up the modem
or turn it on, or whatever).

Probing for best speed to talk to modem: 38400 OK.

About fax classes:

The difference between fax classes has to do with how HylaFAX interacts
with the modem and the fax protocol features that are used when sending
or receiving faxes.  One class isn't inherently better than another;
however, one probably will suit a user's needs better than others.
Class 1 relies on HylaFAX to perform the bulk of the fax protocol.
Class 2 relies on the modem to perform the bulk of the fax protocol.
Class 2.0 is similar to Class 2 but may include more features.
Class 1.0 is similar to Class 1 but may add V.34-fax capability.
Class 2.1 is similar to Class 2.0 but adds V.34-fax capability.
HylaFAX generally will have more features when using Class 1/1.0 than
when using most modems' Class 2 or Class 2.0 implementations.  Generally
any problems encountered in Class 1/1.0 can be resolved by modifications
to HylaFAX, but usually any problems encountered in Class 2/2.0/2.1 will
require the modem manufacturer to resolve it.

If you're unsure and your modem supports it, use Class 1.

This modem looks to have support for Class 1 and 1.0.
How should it be configured [1]? 

Hmm, this looks like a Class 1 modem.
Product code (ATI0) is "spandsp".
Other information (ATI3) is "www.soft-switch.org".
DTE-DCE flow control scheme [default]? 
Modem manufacturer is "spandsp".
Modem model is "IAXmodem".

Using prototype configuration file iaxmodem...

The modem configuration parameters are:

ModemResetCmds:         "ATH1\nAT+VCID=1"

Are these ok [yes]?
The modem was detected and we are asked if it is a Class 1 modem, and we confirm this because it is exactly what we want. The default reset commands are also acceptable. Confirm with yes.
Answer the first question In the next dialog with no, since we don't need to configure any further modems. The second question is confirmed with by pressing Enter, which starts the fax server.
Creating new configuration file /var/spool/hylafax/etc/config.ttyIAX0...
Creating fifo /var/spool/hylafax/FIFO.ttyIAX0 for faxgetty... done.
Done setting up the modem configuration.


Do you want to run faxaddmodem to configure another modem [yes]? no


Should I run faxmodem for each configured modem [yes]? 
/usr/sbin/faxmodem ttyIAX0

Done verifying system setup.

Hylfax is now configured for sending faxes.

Receiving faxes

Our fax solution still has to be integrated into Asterisk. To do this, we configure the IAXmodem as an IAX2 peer by adding a section to /etc/asterisk/iax.conf:
bindport = 4569           
bindaddr =    

Global settings are defined in the general section. In this example we are binding the standard IAX2 port of 4569. The bindaddr defines the IP address (and thereby the interface) on which the IAX2 channel driver listens for connections; in this case, it is set to listen on all interfaces.
The IAXmodem is set to type friend, which allows both incoming and outgoing connections. The secret and port parameters match those in the IAXmodem configuration we did above, and context defines the entry context for outgoing connections.
Enter iax2 show peers in the Asterisk console to see our new IAXmodem:
*CLI> iax2 show peers
Name/Username    Host                 Mask             Port          Status
iaxmodem       (D)  4570          Unmonitored
1 iax2 peers [0 online, 0 offline, 1 unmonitored]
We are, of course, not done yet. Asterisk still needs an extension so that it knows what to do with an incoming fax. Our objective is to ensure that any incoming faxes are passed on to Hylafax. In this example, we assume that all faxes come in through a SIP provider. A real configuration will have to reflect the installation and account settings of the SIP provider you use; for the sake of example, a configuration in sip.conf might look like this:


The corresponding context in extensions.conf would look like this:
exten => _X.,1,Dial(IAX2/iaxmodem)
Any faxes coming in will now be routed to Hylafax via IAXmodem and ultimately e-mailed to the user address defined in the faxmaster alias.

Sending faxes

The next obvious step is configuring our system to send faxes. Here, too, we need a context (this time it is [fax-out]) in extensions.conf. If IAXmodem wants to send a fax, it will automatically land in this context. If the faxes are to go out our hypothetical SIP connection 123456, the entry in extensions.conf will look like this:
exten => _X.,1,Dial(SIP/123456/${EXTEN})
We can test sending of faxes with sendfax -n -d <faxnumber> <file.txt>:
debian:~# sendfax -n -d 6045557977 /etc/issue.net
We should see this in the CLI:
 -- Accepting AUTHENTICATED call from
       > requested format = alaw,
       > requested prefs = (),
       > actual format = alaw,
       > host prefs = (alaw),
       > priority = mine
    -- Executing Answer("IAX2/iaxmodem-3", "") in new stack
    -- Executing Dial("IAX2/iaxmodem-3", "SIP/123456/6045557977") in new stack
    -- Called 123456/6045557977
    -- SIP/123456-0818f630 is making progress passing it to IAX2/iaxmodem-3
    -- SIP/123456-0818f630 answered IAX2/iaxmodem-3
    -- parse_srv: SRV mapped to host my-voip-provider.com, port 5060
  == Spawn extension (fax-out, 6045557977, 2) exited non-zero on 'IAX2/iaxmodem-3'
    -- Executing Hangup("IAX2/iaxmodem-3", "") in new stack
  == Spawn extension (fax-out, h, 1) exited non-zero on 'IAX2/iaxmodem-3'
    -- Hungup 'IAX2/iaxmodem-3'
If we issue the command faxstat -s during the transmission, we will see:
debian:~# faxstat -s
HylaFAX scheduler on w077.example.com: Running
Modem ttyIAX0 (123456): Sending job 7

JID  Pri S  Owner Number       Pages Dials     TTS Status
7    127 R   root 06912345678  0:1   0:12
Done! Now you can send and receive faxes via Asterisk using Hylafax.
The Hylafax website http://www.hylafax.org has numerous examples and how-tos that will help you integrate your Hylafax installation with your existing office intrastructure effectively.

Sending received faxes as e-mail

The following steps illustrate how we can configure Hylafax to transmit incoming faxes to a pre-defined e-mail address.[57]The recipient will receive the fax as an e-mail attachment.
To do this, the configuration file /var/spool/hylafax/etc/FaxDispatch must contain the following parameters:
The destination e-mail address for incoming faxes.
The format of the attachment. In addition to pdf, tiff (Tagged Image File Format) and ps (Postscript™) are also acceptable options.
After the file has been saved, you must restart the fax server with /etc/init.d/hylafax restart.
debian:~# /etc/ini.d/hylafax restart
Starting HylaFAX: faxq hfaxd.
We can test e-mail transmission by sending ourselves a fax with sendfax -n -d <faxnumber> <file.txt>
debian:~# sendfax -n -d 6045557977 /etc/issue.net
After a short time your target e-mail address should receive an e-mail in the following format:
 recvq/fax000000016.tif (ftp://debian:4559/recvq/fax000000016.tif):                                  
          Sender: IAXmodem
           Pages: 4
         Quality: Normal
            Size: North American Letter
        Received: 2007:06:02 02:49:45
 Time To Receive: 1:58
     Signal Rate: 9600 bit/s
     Data Format: 2-D MMR
   Error Correct: Yes
         CallID1: 2007
         CallID2: IAXmodem 1
     Received On: ttyIAX0
          CommID: 000000033 (ftp://debian:4559/log/c000000033)


Jun 02 02:51:46.99: [ 3320]: RECV FAX: bin/faxrcvd "recvq/fax000000016.tif" "ttyIAX0" "000000033" "COMREC received DCN" "2007" "IAXmodem 1" "<NONE>" "s"
Jun 02 02:51:47.00: [ 3320]: RECV FAX: end
Jun 02 02:51:47.00: [ 3320]: SESSION END
Jun 02 02:51:47.01: [ 3320]: RECV FAX (000000033): recvq/fax000000016.tif from IAXmodem, route to <unspecified>, 4 pages in 2:08
The attachment will be a PDF file. In this example, the PDF is named fax000000016.pdf.
Now you can not only send and receive faxes, but received faxes are also received as e-mail attachments.

IAXmodem and Hylafax FAQ


Where does Hylafax save received faxes?


In /var/spool/hylafax/recvq .


Can I use something other than Hylafax?


Yes, absolutely. Nevertheless, Hylafax has proven to be very robust and flexible and is widely used.


Is there an easy to use Faxclient for Windows?


Yes, please have a look at the Hylafax Client page at http://www.hylafax.org/content/Client_Software.


Does Hylafax have its own FAQ?


Yes. You can find it at http://www.hylafax.org/content/FAQ.

[56] May those who have tuned Hylafax before forgive us; for now, the defaults will do.

[57] Our example assumes a properly configured MTA (e.g. Sendmail, Postfix or a lightweight SMTP engine like ssmtp).