Multi-modem and code question

[RD]

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

 

[Dick Grier]

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.