Unable to receive fax

Discussion in '3CX Phone System - General' started by noord, Jan 22, 2016.

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  1. noord

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    Hello all,

    I have everything working just fine and have learned a lot about SIP and VoIP over the past few weeks.
    There is just one aspect of 3CX that I can't seem to get to work: receiving faxes.
    I have a Fax Server set-up, extension 88.

    When I call that extension directly from another phone, the fax picks up and immediately disconnects. There is no fax tone to be heard. I don't know if it's supposed to be like this, or that at least a fax tone should play?

    When I call the extension from outside, using DID, the same happens. The call is answered and dropped immediately.

    The logs look like this (this is when calling from inside with a phone, same entries appear when calling from the outside with an actual fax device):
    Code:
    22-jan-2016 22:50:54.679   [MS105000] C:2.2: No RTP packets were received:remoteAddr=127.0.0.1:13702,extAddr=0.0.0.0:0,localAddr=127.0.0.1:54620
    22-jan-2016 22:50:53.249   Leg L:2.2[Fax] is terminated: Cause: BYE from PBX
    22-jan-2016 22:50:53.248   [CM503008]: Call(C:2): Call is terminated
    22-jan-2016 22:50:53.246   Leg L:2.1[Extn] is terminated: Cause: BYE from PBX
    22-jan-2016 22:50:51.591   [MS205001] C:2.1 RTP: Party address changed from 192.168.1.196:1104 to 82.73.XX.YYY:1104
    22-jan-2016 22:50:50.156   [CM503007]: Call(C:2): Fax:88 has joined, contact <sip:88@127.0.0.1:13006>
    22-jan-2016 22:50:50.153   [CM503007]: Call(C:2): Extn:10 has joined, contact <sip:10@82.73.XX.YYY:5080>
    22-jan-2016 22:50:50.151   L:2.2[Fax] has joined to L:2.1[Extn]
    22-jan-2016 22:50:50.098   [CM503025]: Call(C:2): Calling T:Fax:88@[Dev:sip:88@127.0.0.1:13006;user=phone] for L:2.1[Extn]
    22-jan-2016 22:50:50.047   [CM503027]: Call(C:2): From: Extn:10 ("10" <sip:10@FQDN.FQDN.com:5060>)  to  T:Fax:88@[Dev:sip:88@127.0.0.1:13006;user=phone]
    22-jan-2016 22:50:50.047   [CM503004]: Call(C:2): Route 1: from L:2.1[Extn] to T:Fax:88@[Dev:sip:88@127.0.0.1:13006;user=phone]
    22-jan-2016 22:50:50.046   [CM503001]: Call(C:2): Incoming call from Extn:10 to <sip:88@FQDN.FQDN.com:5060>
    I am using a non-certified SIP Trunk provider, which does support T.38.
    But since I'm getting the same behaviour when calling internally, I'm not even sure that matters.
    To me, it seems like the Fax Server is running in a seperate process on the server and should produce the 'fax welcome tone' when joining any SIP call. But it's not making that sound, so the PBX disconnects the call entirely.
    But I'm not sure if I'm reading this right, if it's supposed to work like this, or something else is up.

    Any help would be greatly appreciated!
     
  2. eagle2

    eagle2 Well-Known Member

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    What 3CX edition are you using ?
    Fax will not work with Free Edition.

    At later stage to check, is your mail server set correctly ?
     
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  3. noord

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    Thanks Eagle.
    I'm using the paid edition, so receiving faxes should work.
    The mail server is set-up correctly, I'm getting all email notifications just fine.

    If you dial your fax extension internally (from another VoIP phone or 3CX softphone), do you get a fax tone or does it just hang-up?
     
  4. eagle2

    eagle2 Well-Known Member

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    If you call the 3CX fax server extension from an IP phone the system will hang-up, if you are calling from analog line (ATA, etc.) you may hear the fax tone. Hearing fax tone also means T.30 fax communication, not T.38 (nothing heart or able to be negotiated in case of dialing from IP phone).
     
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  5. noord

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    Okay, thanks, then that test is inconclusive.
    I obviously first tried sending a real fax to it from a real fax machine and when that didn't work, I tried calling the fax extension from another internal line - but that's not supposed to work anyway.

    Then it remains a bit of a mystery, I'll have to try another SIP trunk then and see if that makes a difference. Or are there some hidden advanced settings regarding the fax server somewhere I could try?
     
  6. Frank D

    Frank D New Member

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    Hi noord,

    we did the following to test faxes: We used a webtofax service to send faxes from external fax machines. There are a lot of free ones e.gl https://www.myfax.com/free/, paid ones offer a better monitoring of the send faxes including error messages. They are only a couple of bucks.

    We used our own Fax-machines to send fax dialing the external numbers. Or just call your fax using mobiles or internal phones using the external number.

    Best regards Frank
     
  7. lneblett

    lneblett Well-Known Member

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    The best thing to do at this point is to do a wireshark capture of an attempted fax reception. From that we can see the details and possibly determine the issue. Just remember to make some of the IP addresses so as to prevent others from trying to hack your system, but at the same time make it so that we can see what device is doing what to whom.
     
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