KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q196096: Client Application Can Use a Modem on SBS for Incoming Calls

Article: Q196096
Product(s): Microsoft Windows NT
Version(s): WINDOWS:95; winnt:4.0,4.0a,4.5
Operating System(s): 
Keyword(s): 
Last Modified: 10-AUG-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft BackOffice Small Business Server versions 4.0, 4.0a, 4.5 
- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows 95 
- Microsoft Windows 98 
-------------------------------------------------------------------------------

SUMMARY
=======

It is possible to run an application on the client computer that monitors a
modem on SBS for incoming calls, such that, when a call comes in, the SBS server
does not answer it but instead the software on the Modem Sharing client senses
it as a call to a directly connected modem and answers it.

MORE INFORMATION
================

Essentially, with the Modem Sharing service, the COM port on the server is being
shared. The client piece simulates an extra communications port on the above
specified clients. Any calls to that simulated local port on the client are
redirected to the Modem Sharing service on the server and subsequently sent to
the shared COM port on the server.

Any application trying to directly access such a port on the client using
hardware calls will fail as this is a simulated COM port available through the
windows environment only. So, only applications that access the port using
windows API calls will work.

Please keep the following in mind:

- Only one client can monitor the modem as it is locked for exclusive use as
  long as the client application is waiting to receive calls. All other
  applications will report this modem as "busy" or "in use" until the client
  application releases it.

- For this reason, the shared modem on the server should not be used for any
  other service except the Modem Sharing service.

To test for proper functioning:

NOTE: The following steps require the Dial-Up Server component of Windows 9x be
installed. This requires Windows 95 Plus! for Windows 95 clients.

1. Set up a modem sharing client on a Windows 9x computer and a shared modem on
  the server.

2. Make sure that the modem is not configured for RAS or fax service on the
  server.

3. Enabled Windows 9x's DialUp Server piece as follows:

  a. Open My Computer.

  b. Open Dial Up Networking.

  c. From the Connections drop down menu, select Dial-Up Server. The shared
     modem should show up as a tab in the Dial-Up Server dialog box.

  d. Select the shared modem.

  e. Configure the modem to receive calls by selecting the Allow Caller Access
     option.

4. Call in to the shared modem's phone line. You should hear modem tones trying
  to negotiate the connection.

5. Set the dial-up server back by clicking to clear the Allow Caller Access
  check box so that it does not answer any calls on the client.

If your application still does not find the COM port, contact the manufacturer to
find out if there is a Windows compliant version of the application.

======================================================================
Keywords          :  
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbAudDeveloper kbWin95search kbWin98search kbSBServSearch kbZNotKeyword3 kbWin98 kbSBServ400 kbSBServ400a kbSBServ450
Version           : WINDOWS:95; winnt:4.0,4.0a,4.5
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.