halting from ppp during GPRS connection - PPP

This is a discussion on halting from ppp during GPRS connection - PPP ; Hello! I have an application on a linux box that opens a GPRS APN via pppd and feeds data to a remote application. At some point of time it is necessary to send a SMS to another destination. The first ...

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Thread: halting from ppp during GPRS connection

  1. halting from ppp during GPRS connection

    Hello!

    I have an application on a linux box that opens a GPRS APN via pppd and
    feeds data to a remote application. At some point of time it is
    necessary to send a SMS to another destination. The first idea that
    came to me was to send a SIGSUSP to pppd, get hold of the modem send
    the SMS and resume pppd.

    Something does not convince me this is the correct way, I suspect I
    would garble thing up at ppp protocol level.

    Any suggestion?

    TIA

    /CM


  2. Re: halting from ppp during GPRS connection

    On 2005-11-05, capitanmutanda@hotmail.com wrote:
    > I have an application on a linux box that opens a GPRS APN via pppd and
    > feeds data to a remote application. At some point of time it is
    > necessary to send a SMS to another destination. The first idea that
    > came to me was to send a SIGSUSP to pppd, get hold of the modem send
    > the SMS and resume pppd.
    >
    > Something does not convince me this is the correct way, I suspect I
    > would garble thing up at ppp protocol level.


    AFAIK, garbling will happen unless you have a way of mixing two link
    layers (RS232 with three wires? Or Bluetooth or even IrDA?) in to one.
    If you're lucky, you'll have two, say, rfcomm links to the modem and you
    can have one for ppp and still send AT commands through the other. Have
    a look at your modem manual. The industrial ones might even have this
    use case documented.

    -Mikko

  3. Re: halting from ppp during GPRS connection


    Mikko Rapeli ha scritto:

    > On 2005-11-05, capitanmutanda@hotmail.com wrote:
    > > I have an application on a linux box that opens a GPRS APN via pppd and
    > > feeds data to a remote application. At some point of time it is
    > > necessary to send a SMS to another destination. The first idea that
    > > came to me was to send a SIGSUSP to pppd, get hold of the modem send
    > > the SMS and resume pppd.
    > >
    > > Something does not convince me this is the correct way, I suspect I
    > > would garble thing up at ppp protocol level.

    >
    > AFAIK, garbling will happen unless you have a way of mixing two link
    > layers (RS232 with three wires? Or Bluetooth or even IrDA?) in to one.
    > If you're lucky, you'll have two, say, rfcomm links to the modem and you
    > can have one for ppp and still send AT commands through the other. Have


    Mikko thanks for your reply. If I understand corectly I could get hold
    of the phone modem via bluetooth, simply with a dongle on my PC, and
    send the SMS that way. However there is a fly in the ointment... as a
    prototype this is ok but the production thing does not have these
    capabilities (arm embedded linux on a very small board --> low cost).

    What I need to do is send via SMS the IP address received from the
    GGSN. I'm afraid that I have only one way out and have to build some
    sort of extension to pppd so that when it receives SIGUSR2 it will +++
    the modem send the SMS and resume ppp

    I was trying to avoid the NIH syndrome....

    Tnx
    /CM

    so that is


  4. Re: halting from ppp during GPRS connection

    On 2005-11-06, Capitan Mutanda wrote:
    > What I need to do is send via SMS the IP address received from the
    > GGSN. I'm afraid that I have only one way out and have to build some


    If the IP address resolution is the only requirement for an SMS, then I'd use a
    dynamic DNS service instead, but even that suggest you get a public IP address
    from the GPRS network and that the GGSN allows inbound (TCP?) traffic.
    These assumptions usually cost money in subscription at least, so I'd
    use a central server to which mobile clients connect even from NAT and
    HTTP proxy networks -- but these issues of course depend on the actual
    application too.

    > sort of extension to pppd so that when it receives SIGUSR2 it will +++
    > the modem send the SMS and resume ppp


    Linux side won't be the problem, I think. It's the GPRS modem. In needs to
    keep the PPP state too.

    The guys with more PPP knowledge can perhaps comment more on this...

    -Mikko

  5. Re: halting from ppp during GPRS connection


    Mikko Rapeli ha scritto:

    > On 2005-11-06, Capitan Mutanda wrote:
    > > What I need to do is send via SMS the IP address received from the
    > > GGSN. I'm afraid that I have only one way out and have to build some

    >
    > If the IP address resolution is the only requirement for an SMS, then I'd use a
    > dynamic DNS service instead, but even that suggest you get a public IP address
    > from the GPRS network and that the GGSN allows inbound (TCP?) traffic.


    Some mobile operators permit traffic flow between terminals on the same
    GPRS core net.
    This functionality is a configuration parameter in GGSN (at least in
    Nokia GGSN)
    so I can avoid public IPs and just need to stay within the same mobile
    net.

    It would be much easier if I had the GGSN establish a tunnel directly
    to a server somewhere on the net with a public IP; it could then act as
    a router. But this means
    much more money and arrangements with mobile operators. The central
    server would also be a single point of failure or need cluster and
    similar stuff for reliability.

    What I'm trying to do is a sort of P2P with this fly in the ointment
    due to the variable IP address the GGSN could assign me

    /CM


  6. Re: halting from ppp during GPRS connection

    On 2005-11-06, Capitan Mutanda wrote:
    > What I'm trying to do is a sort of P2P with this fly in the ointment
    > due to the variable IP address the GGSN could assign me


    Yes, it's a lot trickier to have a server in the mobile host.

    Good luck,

    -Mikko

  7. Re: halting from ppp during GPRS connection

    capitanmutanda@hotmail.com napisaƂ(a):
    > Hello!
    >
    > I have an application on a linux box that opens a GPRS APN via pppd and
    > feeds data to a remote application. At some point of time it is
    > necessary to send a SMS to another destination. The first idea that
    > came to me was to send a SIGSUSP to pppd, get hold of the modem send
    > the SMS and resume pppd.
    >
    > Something does not convince me this is the correct way, I suspect I
    > would garble thing up at ppp protocol level.
    >
    > Any suggestion?
    >
    > TIA
    >
    > /CM
    >


    Depending on a mobile phone/modem you are using, it may support
    multiplexing protocol which should give you 3 (at least in case of
    siemens gsm module) virtual serial ports. One can be used for GPRS
    others for other tasks such as SMS (manual should give you info what
    can/cannot be on each virtual serial ports). As for drivers, they are
    available for Windows (have not seen for Linux but it does not mean they
    are not available) along with source code. Multiplexing protocol itself
    is also described somewhere - in case no Linux implementation available.

    Maciek.

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