command mode during connection - PPP

This is a discussion on command mode during connection - PPP ; Is there any chance to get to command mode during a ppp connection ? i.e. i have to control signal level during a a gprs ppp connection but couldn't find a way to send the escape sequence to the modem. ...

+ Reply to Thread
Results 1 to 10 of 10

Thread: command mode during connection

  1. command mode during connection

    Is there any chance to get to command mode during a ppp connection ?
    i.e. i have to control signal level during a a gprs ppp connection
    but couldn't find a way to send the escape sequence to the modem.
    Does this somehow violate the protocol or simply i didn't try
    hard enough ?

  2. Re: command mode during connection

    "carlo" writes:
    > Is there any chance to get to command mode during a ppp connection ?
    > i.e. i have to control signal level during a a gprs ppp connection
    > but couldn't find a way to send the escape sequence to the modem.
    > Does this somehow violate the protocol or simply i didn't try
    > hard enough ?


    You didn't say what kind of system you're using ... or, really, much
    about what equipment you're using.

    Yes, it's at least possible in theory. The three ways I know of to do
    it are:

    - Modify the AHDLC encoder (typically in the kernel on a UNIX
    or Unix-like machine) so that it's able to insert the Hayes
    TIES sequence (pause-+++-pause) into the data stream to go
    into command mode, issue the AT commands desired, then issue
    ATO to go back on-line.

    - Change the modem configuration so that dropping DTR returns
    to command mode rather than hanging up (AT&D1 on most modern
    modems). Modify the AHDLC encoder so that it can drop DTR,
    pause, send AT commands, then raise DTR, send ATO, and
    continue.

    - Get a modem that has separate control and data channels.
    I've seen this on commercial modems used for servers. Then
    you can issue AT commands any time you want.

    The first two likely aren't terribly reliable, but could be made to
    work with some hackery. The last one works very well, but I've only
    seen it in custom designs, so I can't help you there.

    --
    James Carlson, KISS Interop
    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

  3. Re: command mode during connection

    Il Tue, 12 Apr 2005 07:31:02 -0400, James Carlson ha scritto:


    > You didn't say what kind of system you're using ... or, really, much
    > about what equipment you're using.

    it's a telit gprs modem on pc104 board which emulates a serial port


  4. Re: command mode during connection

    "carlo" writes:
    > Il Tue, 12 Apr 2005 07:31:02 -0400, James Carlson ha scritto:
    >
    >
    > > You didn't say what kind of system you're using ... or, really, much
    > > about what equipment you're using.

    > it's a telit gprs modem on pc104 board which emulates a serial port


    Do you have an operating system?

    --
    James Carlson, KISS Interop
    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

  5. Re: command mode during connection

    carlo wrote:
    > Is there any chance to get to command mode during a ppp connection ?
    > i.e. i have to control signal level during a a gprs ppp connection
    > but couldn't find a way to send the escape sequence to the modem.
    > Does this somehow violate the protocol or simply i didn't try
    > hard enough ?



    Escape to command mode is just a normal +++ with appropriate quiet time
    delay before.

    However, return to PPP stage does not get you to the point where you
    left, instead it will "restart" PPP as such (at least it does so on
    modems that I am using)

    If modem you are using supports multiplexing protocol then you can do it
    without killing PPP. On one physical serial port you can run up to 3
    virtual serial ports, however you would have to embed all traffic into
    this multiplexing protocol, thus write some soft of virtual rs devices
    or modify PPP implementation itself to support this functionality.

    Maciek.

  6. Re: command mode during connection

    Il Tue, 12 Apr 2005 09:10:28 -0400, James Carlson ha scritto:

    > "carlo" writes:
    >> Il Tue, 12 Apr 2005 07:31:02 -0400, James Carlson ha scritto:
    >>
    >>
    >> > You didn't say what kind of system you're using ... or, really, much
    >> > about what equipment you're using.

    >> it's a telit gprs modem on pc104 board which emulates a serial port

    >
    > Do you have an operating system?

    Ops.. it's a modified version of a rh 7.3 with a 2.4.28 vanilla,
    and pppd 2.4.3
    which runs on a cyrix cpu.
    The machine is a sort of shoes box with an lcd touch screen, it has
    to connect while moving in industrial environments where signal power
    may change often during connection. We have to monitor it,but didn't
    find a way
    Thanks for any help

  7. Re: command mode during connection

    "carlo" wrote in message news:...
    > Is there any chance to get to command mode during a ppp connection ?
    > i.e. i have to control signal level during a a gprs ppp connection
    > but couldn't find a way to send the escape sequence to the modem.
    > Does this somehow violate the protocol or simply i didn't try
    > hard enough ?


    not really. you need to switch back to command mode and break the ppp
    link.

    The Siemens TC45 allows you to run Java on the modem and you can then
    send AT commands (from within the Java).

  8. Re: command mode during connection

    "carlo" writes:

    >Is there any chance to get to command mode during a ppp connection ?
    >i.e. i have to control signal level during a a gprs ppp connection
    >but couldn't find a way to send the escape sequence to the modem.
    >Does this somehow violate the protocol or simply i didn't try
    >hard enough ?


    No, you cannot. What in the world would the modem do with all the junk ppp
    is trying to send to it, when it is suddenly in command mode.
    If you could get a modem which had two different connections-- eg two
    serial lines-- one for comand and the other for data, you might.


  9. Re: command mode during connection

    Unruh writes:
    > "carlo" writes:
    >
    > >Is there any chance to get to command mode during a ppp connection ?
    > >i.e. i have to control signal level during a a gprs ppp connection
    > >but couldn't find a way to send the escape sequence to the modem.
    > >Does this somehow violate the protocol or simply i didn't try
    > >hard enough ?

    >
    > No, you cannot. What in the world would the modem do with all the junk ppp
    > is trying to send to it, when it is suddenly in command mode.


    Decent modems end up asserting flow control in that case. The V.42
    window will close up, and the peer will be unable to send more data.
    As long as the outage is "brief" and the modem firmware is reasonably
    well-implemented, it shouldn't cause serious trouble. I do agree,
    though, that you probably would want to try to extract this data only
    when the link was relatively idle.

    > If you could get a modem which had two different connections-- eg two
    > serial lines-- one for comand and the other for data, you might.


    Yes, that's the good way to do it.

    --
    James Carlson, KISS Interop
    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

  10. Re: command mode during connection

    Il Tue, 12 Apr 2005 11:27:20 +0200, carlo ha scritto:

    > Is there any chance to get to command mode during a ppp connection ?
    > i.e. i have to control signal level during a a gprs ppp connection
    > but couldn't find a way to send the escape sequence to the modem.
    > Does this somehow violate the protocol or simply i didn't try
    > hard enough ?

    thank you everybody for help

+ Reply to Thread