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Hi Markus,<br>
<br>
Thanks for having replied in such a comprehensible way, this is very
clear to me now.<br>
<br>
Best regards<br>
Florent<br>
<br>
<div class="moz-cite-prefix">Le 13/05/2014 15:28, Markus Lindenberg
a écrit :<br>
</div>
<blockquote
cite="mid:CAExAoeCca=fCgq-ZJAwivAOv0GVSKZzTxm4Qbpqn3Odj75jVog@mail.gmail.com"
type="cite">
<div dir="ltr">Hi Florent,
<div><br>
</div>
<div>as you might know HylaFAX is a fax server suite for Unix.
It is over 20 years old but still actively developed, and it
is *very* stable and widely used. Hylafax consists of a few
daemons and tools that interact. It provides a FTP-based
network protocol to submit faxes from desktop clients or other
systems, a scheduler that schedules sending of queued faxes
and dealing with failed transmissions and backends to interact
with fax modems. </div>
<div><br>
</div>
<div>The most important components are:</div>
<div><br>
</div>
<div>faxq - qeuue manager daemon for outgoing faxes</div>
<div>hfaxd - network protocol server daemon (receives jobs and
hands them to faxq)</div>
<div>
<br>
</div>
<div>faxgetty - modem daemon (one faxgetty waits for incoming
faxes on one particular modem)</div>
<div>faxsend - open a modem device and send outgoing faxes
through that modem</div>
<div><br>
</div>
<div>As 20 years ago fax always meant using fax modems, HylaFax
is natively made to (only) work with fax modems through it's
faxgetty and faxsend processes. To use those, you *have* to
have one or more fax modems that are connected/exposed through
a serial interface (/dev/tty* on Linux). </div>
<div><br>
</div>
<div>FreeSWITCH with its spandsp module can already provide a
number of virtual modems that HylaFAX can use, see <a
moz-do-not-send="true"
href="http://wiki.freeswitch.org/wiki/HylaFax">http://wiki.freeswitch.org/wiki/HylaFax</a>.
Connecting HylaFax and FreeSWITCH using tty devices has some
drawbacks as i mentioned. </div>
<div><br>
</div>
<div>The interface of faxgetty and faxsend is pretty easy to
implement, faxsend is called by faxq, it will take a .tiff fax
file and send it using a fax modem. faxgetty will receive a
fax and place a .tiff file in HylaFax' spool directory. After
receiving, it will call a shell script that can dispatch the
fax (send it by mail, print it etc.). </div>
<div><br>
</div>
<div>What I did here was reimplement those two commands:</div>
<div><br>
</div>
<div>gofaxd - replacement for one or more faxgetty processes</div>
<div>gofaxsend - replacement for faxsend</div>
<div><br>
</div>
<div>
The two replacement commands will talk to FreeSWITCH through
the event socket and send/receive faxes using mod_spandsp's
rxfax/txfax applications. This has a few advantages over using
tty devices to connect to FreeSWITCH:</div>
<div><br>
</div>
<div>- No Fax modem emulation and tty device necessary (thus the
stack becomes simpler)</div>
<div>- Native T.38 without t38_gateway (more robust and less CPU
usage)</div>
<div>- We can use and log all sorts of events and verbose
debugging (SIP headers, bad rows etc.) to HylaFax. </div>
<div>- Number of parallel incoming faxes not limited by number
of virtual modems. </div>
<div><br>
</div>
<div>The concept was used before in the open source capi4hylafax
suite that implemented c2faxsend and c2faxrcvd as replacement
for faxsend and faxgetty. capi4hylafax could talk to ISDN CAPI
2.0 devices instead of tty fax modems. </div>
<div><br>
</div>
<div>Compared to t38modem or iaxmodem, which (as far as i know)
are not maintained anymore, the beauty in this system is that
- apart from some decent FreeSWITCH and HylaFax knowledge
needed to implement it - all the hard stuff (signal
processing) is done in FreeSWITCH and mod_spandsp with both
are actively maintained and improved. GOfax.IP is only
shifting metadata like logs and queue files around and helping
HylaFax and FreeSWITCH talk to each other. That's not much
more than basic text processing, so it's easy to maintain and
easy to improve without deeper knowledge of Fax protocols,
spandsp etc. </div>
<div><br>
</div>
<div>The remaining question is if it is a good idea to use
HylaFax for new projects at all. If I have to implement a new
receive only fax system, I'd probably just use rxfax in the
dialplan and a Lua script to process the fax and be done with
it. I've done that before and it's easy to implement and works
really well. </div>
<div>The reason why we've built GOfax.IP is that we have a
larger amount of existing HylaFax setups that have been
running for years (or even decades) with existing
incoming/outgoing document handling based on HylaFax.
Customers trust HylaFax and hesitate to completely redesign
their fax processing when wanting to move from legacy analog
modems or ISDN to Fax over IP. So it's more agreeable to all
parties involved to switch the PSTN connectivity in HylaFax
than deploy a completely different solution.</div>
<div><br>
</div>
<div>Best regards, </div>
<div><br>
</div>
<div>Markus</div>
<div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Fri, May 9, 2014 at 5:31 PM,
Florent Krieg <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:fkrieg@sewan.eu"
target="_blank">fkrieg@sewan.eu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF"> Hi Markus,<br>
<br>
I don't know very well HylaFAX. How is your soft
related to it? You tell us about 'backend' but that
doesn't really help a novice like me. <br>
I'd be grateful if you could tell me briefly what are
their roles (how they interact together).<br>
<br>
Thanks in advance!<br>
<br>
Best regards,<br>
Florent<br>
<br>
<div>Le 09/05/2014 13:47, Markus Lindenberg a écrit :<br>
</div>
<blockquote type="cite">
<div>
<div class="h5">
<div dir="ltr">Hi,
<div><br>
</div>
<div>
<div>We just open sourced GOfax.IP, a
project i've been working on for the
better part of the last two months. </div>
<div>It's a new (and I think best yet) way
to bring "native" Fax over IP using T.38
or G711 to HylaFAX Fax servers by directly
connecting HylaFAX to FreeSWITCH's
mod_spandsp without any modem emulation
layer.</div>
<div><br>
</div>
<div>We replaced the faxgetty and faxsend
processes with versions that use
FreeSWITCH to handle incoming and outgoing
calls. </div>
<div><br>
</div>
<div><a moz-do-not-send="true"
href="https://github.com/gonicus/gofaxip"
target="_blank">https://github.com/gonicus/gofaxip</a><br>
</div>
<div><br>
</div>
<div>We wanted to have a solution that
brings all the power of rxfax/tfax to
HylaFax. FreeSWITCH's modem emulation has
to be chained to t38_gateway to use T.38,
and in my tests that didn't work as well
as using txfax/rxfax, so I looked at how
capi4hylafax hooks into HylaFax and
implemented that approach for FreeSWITCH. </div>
<div><br>
</div>
<div>I'd love to hear thoughts/suggestions
and am happy to accept bug reports and
contributions.</div>
<div><br>
</div>
<div>Regards, </div>
</div>
<div><br>
</div>
<div>Markus</div>
</div>
<br>
<fieldset></fieldset>
<br>
</div>
</div>
<pre>_________________________________________________________________________
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<a moz-do-not-send="true" href="http://www.freeswitchsolutions.com" target="_blank">http://www.freeswitchsolutions.com</a>
FreeSWITCH-powered IP PBX: The CudaTel Communication Server
<a moz-do-not-send="true" href="http://www.cudatel.com" target="_blank">http://www.cudatel.com</a>
Official FreeSWITCH Sites
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FreeSWITCH-users mailing list
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</pre>
<br>
<span class=""><font color="#888888">
<pre cols="72">--
Florent Krieg
Sewan Communications - Ingénieur R&D</pre>
</font></span></blockquote>
</div>
<br>
_________________________________________________________________________<br>
Professional FreeSWITCH Consulting Services:<br>
<a moz-do-not-send="true"
href="mailto:consulting@freeswitch.org">consulting@freeswitch.org</a><br>
<a moz-do-not-send="true"
href="http://www.freeswitchsolutions.com"
target="_blank">http://www.freeswitchsolutions.com</a><br>
<br>
FreeSWITCH-powered IP PBX: The CudaTel Communication
Server<br>
<a moz-do-not-send="true" href="http://www.cudatel.com"
target="_blank">http://www.cudatel.com</a><br>
<br>
Official FreeSWITCH Sites<br>
<a moz-do-not-send="true"
href="http://www.freeswitch.org" target="_blank">http://www.freeswitch.org</a><br>
<a moz-do-not-send="true"
href="http://wiki.freeswitch.org" target="_blank">http://wiki.freeswitch.org</a><br>
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<br>
</blockquote>
</div>
<br>
</div>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_________________________________________________________________________
Professional FreeSWITCH Consulting Services:
<a class="moz-txt-link-abbreviated" href="mailto:consulting@freeswitch.org">consulting@freeswitch.org</a>
<a class="moz-txt-link-freetext" href="http://www.freeswitchsolutions.com">http://www.freeswitchsolutions.com</a>
FreeSWITCH-powered IP PBX: The CudaTel Communication Server
<a class="moz-txt-link-freetext" href="http://www.cudatel.com">http://www.cudatel.com</a>
Official FreeSWITCH Sites
<a class="moz-txt-link-freetext" href="http://www.freeswitch.org">http://www.freeswitch.org</a>
<a class="moz-txt-link-freetext" href="http://wiki.freeswitch.org">http://wiki.freeswitch.org</a>
<a class="moz-txt-link-freetext" href="http://www.cluecon.com">http://www.cluecon.com</a>
FreeSWITCH-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:FreeSWITCH-users@lists.freeswitch.org">FreeSWITCH-users@lists.freeswitch.org</a>
<a class="moz-txt-link-freetext" href="http://lists.freeswitch.org/mailman/listinfo/freeswitch-users">http://lists.freeswitch.org/mailman/listinfo/freeswitch-users</a>
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</pre>
<br>
<pre class="moz-signature" cols="72">--
Florent Krieg
Sewan Communications - Ingénieur R&D</pre>
</blockquote>
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