Client Application Can Use a Modem on SBS for Incoming Calls (196096)


The information in this article applies to:

  • Microsoft BackOffice Small Business Server 4.0
  • Microsoft BackOffice Small Business Server 4.0a
  • Microsoft BackOffice Small Business Server 4.5
  • Microsoft Windows NT Workstation 4.0
  • Microsoft Windows 95
  • Microsoft Windows 98
This article was previously published under Q196096

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:

    1. Open My Computer.
    2. Open Dial Up Networking.
    3. 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.
    4. Select the shared modem.
    5. 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.
Modification Type:MinorLast Reviewed:12/16/2004
Keywords:kbinfo KB196096
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