Multi-modem and code question

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  • RD
    #1

    Multi-modem and code question

    I have a requirement to develop an app in Vb.Net that will use a multi-line
    (4 or 8 port) modem on which outside users will be able to dial in and send
    data files. The app just needs to be listening, respond to an incomming call
    when it occurs and store the received data in a file. I have an existing app
    that does this in VB6 but it uses only a single modem with one telephone
    line.

    I've been looking at some docs on multi modems (4 or 8 lines) but they all
    seem to directed to be used as RAS ports.

    Can anyone recommend an appropriate hardware product for this type of
    project and possible direct me to some sample code that would let me start
    on an app that can handle a number of simultaneous incoming data transfers
    via this type of card?

    Any help would be greatly appreciated

    RD


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    • Dick Grier
      #2
      Re: Multi-modem and code question

      Hi,

      Quatech (www.quatech.com), SeaLevel (www.sealevel.com), and Inside Out
      Networks (www.ionetworks.com) all have multiple serial port solutions (there
      are others). Multiple modem cards are much less common, and these tend to
      use lower-speed modems with older technology, or are quite expensive for UTD
      designs. I suggest the multi-serial port approach, with external modems --
      a single card with internal modems also will cost quite a bit more (example:
      RocketModem 8-port cards cost over $2K).

      Writing the code to use multiple-modems is straight-forward, but you have to
      realize that serial communications can be fairly intensive, especially if
      you want to employ error corrected file transfers. IMO, eight modems per PC
      is the maximum that I'd attempt -- which suits your requirements. After
      that, the actual design will depend on more than you've describe. However,
      feel free to ask questions and I'll try to help.

      Dick

      --
      Richard Grier (Microsoft Visual Basic MVP)

      See www.hardandsoftware.net for contact information.

      Author of Visual Basic Programmer's Guide to Serial Communications, 4th
      Edition ISBN 1-890422-28-2 (391 pages) published July 2004. See
      www.mabry.com/vbpgser4 to order.


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