zmodem - PPP

This is a discussion on zmodem - PPP ; hi, im in need to know some information about how to use the modem to communicate with another machine ( with a modem) using low level API to control the modem. i've heard about zmodem, xmodem, etc, but dont know ...

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Thread: zmodem

  1. zmodem

    hi,
    im in need to know some information about how to use the modem to
    communicate with another machine ( with a modem) using low level API to
    control the modem. i've heard about zmodem, xmodem, etc, but dont know
    the api they use to comminicate with the modem. Please can someone give
    me a starting point?

    CMOS


  2. Re: zmodem

    manusha@millenniumit.com writes:

    >hi,
    >im in need to know some information about how to use the modem to
    >communicate with another machine ( with a modem) using low level API to
    >control the modem. i've heard about zmodem, xmodem, etc, but dont know
    >the api they use to comminicate with the modem. Please can someone give
    >me a starting point?


    They send text AT commands to the modem via the serial line. There is no
    low level api -- the modem is a remote piece of hardware.
    Once the modem has connected with the remote machine, then you just read
    and write the stuff you want to the serial port and it will be sent to the
    other machine.
    Why you would want to use zmodem or whatever now that ppp is available to
    establish a full TCPIP link I have no idea. And why you would ask in a ppp
    newgroup is also obscure.
    >CMOS



  3. Re: zmodem

    manusha@millenniumit.com writes:
    > im in need to know some information about how to use the modem to
    > communicate with another machine ( with a modem) using low level API to
    > control the modem. i've heard about zmodem, xmodem, etc, but dont know
    > the api they use to comminicate with the modem. Please can someone give
    > me a starting point?


    You may need to look elsewhere, as your question seems to have nothing
    to do with PPP, which is the topic for this newsgroup.

    Modems don't have low-level APIs. Operating systems, though, may well
    have APIs or other features for use with serial ports in general or
    specifically with modems. Your first stopping point should be the
    technical documentation for the system you're trying to use. (You
    didn't mention what operating system you might be using, so it's
    almost impossible to give any advice here. And even if you had, this
    newsgroup is the wrong place to ask the question.)

    Zmodem and Xmodem are file transfer protocols, not APIs. They don't
    control modems at all. Instead, simply put, they're an ancient way to
    encode files as a stream of characters so that you can transfer them
    over a serial connection between two machines. The word "modem" in
    the name refers to the fact that users often wanted to transfer files
    between systems using modems (e.g., dial up BBSes), and that's the
    problem these protocols solved.

    Kermit and BLAST are other examples of such a protocol. UUCP is
    similar.

    PPP is something different. It's a networking protocol. It turns a
    serial interface (such as one over a modem) into a network interface
    that can be used by network layer protocols, such as IP, IPX,
    AppleTalk, OSI, SNA, DECNet, and others.

    --
    James Carlson, KISS Network
    Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

  4. Re: zmodem

    Unruh writes:
    > They send text AT commands to the modem via the serial line.


    Usually true, though for embedded systems this need not be true.

    > There is no
    > low level api -- the modem is a remote piece of hardware.


    That depends. Some OSes likely provide high-level modem control APIs.
    I believe this is available on Windows. System V systems have the old
    dial(3NSL) library routines. I don't think Linux has anything like
    this, though.

    > Once the modem has connected with the remote machine, then you just read
    > and write the stuff you want to the serial port and it will be sent to the
    > other machine.
    > Why you would want to use zmodem or whatever now that ppp is available to
    > establish a full TCPIP link I have no idea. And why you would ask in a ppp
    > newgroup is also obscure.


    It just depends on what the remote system needs. There might still be
    systems in the world that need only simple file transfer and not a
    full networking stack. X-Modem or one of the others would solve that
    problem nicely. (I'm partial to Kermit, but then I never did like
    those CP/M things.)

    --
    James Carlson, KISS Network
    Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

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