How Modem Sharing Client Queries for Devices on SBS

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When querying local COM ports, the status of the port is returned instantaneously. Because the SBS modem sharing client redirects COM port communications to the SBS server where the real modem exists, querying the status of a remote port may take longer. It requires sending a status request to the server and then waiting for a reply from the server. The operation is completed when the server replies with the required data.

The modem sharing device driver requires that all status queries to be synchronous. That is, the modem sharing device driver must wait for the reply from the server before returning to the caller. If the reply from the server takes too long, the application request may timeout.