[asterisk-dev] Fax with Asterisk and T38Modem

[Steve Totaro]

On Wed, Jun 29, 2011 at 5:57 PM, Thorolf Godawa <nospam at godawa.de> wrote:

> Hi,
>
> I'm fighting with HylaFAX, Asterisk and T38Modem since some time, to get
> fax2mail and mail2fax working, my SIP-provider only supports T38 and
> thus using G711 with IAXModem is not an option.
>
>
> I have got running mail2fax with HylaFAX+ 5.5.0, Asterisk 1.4.20 and
> T38Modem 2.0.0 successfull, but I'm not able to upgrade to anything
> newer than Asterisk 1.4.24.
>
> I was able to track down this problem to some changes in the chan_sip.c,
> where a "improved support for T38 on initial INVITE" has been
> implemented, see:
> <https://reviewboard.asterisk.org/r/208/diff/#index_header>
>
> I'm not sure what the problem is, but it seems that the T38 handshake
> does not work correct any more bacause the CFR (confirm to receive) is
> missing.
>
> Goal is, to get running this with the latest Asterisk, right now
> 1.8.4.4. Is there s.b. who can give me a hint how to solve the problem?
>
>
> For fax2mail I use Asterisk 1.8.4.4, but it is not working too, after a
> fax call, the connection with T38Modem is established, HylaFAX reports
> "ANSWER: FAX CONNECTION DEVICE '/dev/ttyT380'", but a fax is never
> received.
>
> In the tcpdump I see the correct handshaking between Asterisk and
> T38Modem, but finaly T38Modem makes a second REINVITE with "recvonly"
> and Asterisk answers with "SIP/2.0 488 Not acceptable here" and the call
> ends shortly after that.
>
> As far as I can see, does not accept the portchange from rtp to
> udtpl and thus tries a REINVITE. Probably there is a problem in
> T38Modem, so I filed a bug at sourceforge for that:
>
>
> https://sourceforge.net/tracker/?func=detail&aid=3337581&group_id=152230&atid=783657
>
> But may be, somebody has a solution for this too.
>
>
> Thanks a lot,
> --
>
> Chau y hasta luego,
>
> Thorolf
>
>
Have you seen this -
http://www.foriamroot.org/hylafax-6-0-debian-or-ubuntu-t38modem-1-0-asterisk-1-6/?
 It is a good read.

I am not sure why you don't use ulaw between Asteirsk and Hylafax.

I use IAXmodem and hylafax, so I am no expert on T38Modem, but same concept.

I found this nugget of info

"Remember the BIND_IP configured on the t38modem startup script mentioned
above? You need to set the same here so that asterisk can contact T38modems.

Also please note that you need to set canreinvite = no for t38modem to work.
Additionally if the incoming calls arrive in G.729 you need to have a G.729
codec installed on your asterisk in order for T38modem to do a T.38
Re-Invite back."

T38Modem is just a virtual modem and sip client that talks to Asterisk
T38..  There is no reason that you cannot use ulaw between asterisk and
Hylafax.

I always use a second NIC and a crossover cable unless the customer doesn't
need it or want it
Let T38Modem handle the T38 between the carrier and you.  If everything is
running on the same box, you should have no issues as long as the server is
powerful enough.

You most likely have canreinvite set to yes in your sip.conf for that
modem.

If you post more details, like what you were upgrading, logs, debugging info
and conf files, will you get your answers much faster.

Please post if you make any progress or find a solution so people don't have
to think for themselves anymore.

The dumbing down of Asterisk professionals.  It gives Asterisk a bad name
when they don't want to learn or understand, they want to be spoon fed.

Anyways, I cannot complain too much because I have made some decent scratch
by fixing simple problems that somebody who has nothing but google to feed
them answers.  No imagination or experimentation.

Thanks,
Steve Totaro
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