Detecting incoming calls while GPRS - PPP

This is a discussion on Detecting incoming calls while GPRS - PPP ; I think this is quite impossible, but I have to ask because this would simplify a lot my project: When I am connected to Internet via GPRS, is there any way of pppd to realize that we have an incoming ...

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Thread: Detecting incoming calls while GPRS

  1. Detecting incoming calls while GPRS

    I think this is quite impossible, but I have to ask because this would
    simplify a lot my project:

    When I am connected to Internet via GPRS, is there any way of pppd
    to realize that we have an incoming data call and let me answer it?
    (simply terminating itself and let the ttySx free for my use)


    Lot of thanks for any response

    Jorge

  2. Re: Detecting incoming calls while GPRS

    pancho wrote:
    > I think this is quite impossible, but I have to ask because this would
    > simplify a lot my project:


    > When I am connected to Internet via GPRS, is there any way of pppd
    > to realize that we have an incoming data call and let me answer it?
    > (simply terminating itself and let the ttySx free for my use)


    How could there be a way?

    It seems to me that as long as the PPP connection exists it uses the
    "physical layer" of the GPRS connection (or any other connection)
    and prevents the phone from answering calls - the calling end will
    get a BUSY signal. In the absence of call-waiting notification, how
    could anything detect an incoming call unless the phone is "on hook?"
    Pppd certainly cannot detect call-waiting notification.

    -- Clifford Kite Email: "echo xvgr_yvahk-ccc@ri1.arg|rot13"
    PPP-Q&A links, downloads: http://ckite.no-ip.net/
    /* The signal-to-noise ratio is too low in many [news] groups to make
    * them good candidates for archiving.
    * --- Mike Moraes, Answers to FAQs about Usenet */

  3. Re: Detecting incoming calls while GPRS

    Clifford Kite writes:
    > It seems to me that as long as the PPP connection exists it uses the
    > "physical layer" of the GPRS connection (or any other connection)
    > and prevents the phone from answering calls - the calling end will
    > get a BUSY signal.


    Not necessarily. If you have call waiting, the other party will get a
    ringing signal, while your connection gets periodically disrupted with
    the familiar "beep." Dunno how or if that works for GPRS, though.

    > In the absence of call-waiting notification, how
    > could anything detect an incoming call unless the phone is "on hook?"


    Agreed; if you don't have call-waiting, or some other out-of-band
    notification mechanism (how is call control done with GPRS?), then
    you're sunk.

    > Pppd certainly cannot detect call-waiting notification.


    I don't think that's true. There's no reason a modem on a regular
    POTS line couldn't detect the call-waiting tone and signal the client
    appropriately. The only other thing that'd be needed would be some
    hacks to the kernel portion of pppd (original poster didn't say, but I
    assume he's using some Linux variant) that detect this message and
    switch over.

    To make it reliable, you'd have to find some way of making sure that
    the in-band signal cannot possibly ever be a part of the data portion
    of a legitimate PPP packet. One way to do that would be to frame it
    with control characters that are (intentionally) always escaped.

    I don't know of any hacks to pppd or the kernel bits to do this,
    though. It's a frequently-asked question, but nobody with both the
    modems in question and the spare time to do the implementation seems
    to have come forward yet.

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

  4. Re: Detecting incoming calls while GPRS

    James Carlson wrote:
    > Clifford Kite writes:


    >> Pppd certainly cannot detect call-waiting notification.


    > I don't think that's true. There's no reason a modem on a regular
    > POTS line couldn't detect the call-waiting tone and signal the client
    > appropriately. The only other thing that'd be needed would be some
    > hacks to the kernel portion of pppd (original poster didn't say, but I
    > assume he's using some Linux variant) that detect this message and
    > switch over.


    In my defense, I meant pppd as it is currently coded - which is true.

    --
    Clifford Kite Email: "echo xvgr_yvahk-ccc@ri1.arg|rot13"
    PPP-Q&A links, downloads: http://ckite.no-ip.net/
    /* They that can give up essential liberty to obtain a little temporary
    safety deserve neither liberty nor safety." Benjamin Franklin */


  5. Re: Detecting incoming calls while GPRS

    El Wed, 28 Jul 2004 08:51:13 -0400, James Carlson escribió:

    >> Pppd certainly cannot detect call-waiting notification.

    >
    > I don't think that's true. There's no reason a modem on a regular
    > POTS line couldn't detect the call-waiting tone and signal the client
    > appropriately. The only other thing that'd be needed would be some
    > hacks to the kernel portion of pppd (original poster didn't say, but I
    > assume he's using some Linux variant) that detect this message and
    > switch over.
    >
    > To make it reliable, you'd have to find some way of making sure that
    > the in-band signal cannot possibly ever be a part of the data portion
    > of a legitimate PPP packet. One way to do that would be to frame it
    > with control characters that are (intentionally) always escaped.
    >
    > I don't know of any hacks to pppd or the kernel bits to do this,
    > though. It's a frequently-asked question, but nobody with both the
    > modems in question and the spare time to do the implementation seems
    > to have come forward yet.


    Lot of thanks for your response and the Clifford one. So the conclusion is
    what I thought: it would be physically possible but pppd doesn't support
    this.

    I am using uClinux (I work on an embedded system). I would like to have
    the knowledge and the time to add this feature to ppp, but for now my
    device simply won't answer the calls while using Internet.

    Best regards,

    Jorge

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