Modem Manager Concepts

Client Server Relationships

The Modem Manager runs as a server on one system and as a client on others. The server and client Modem Managers cooperate to provide modem pool management and to set up data paths between modem users and the allocated modem(s).

Outgoing Calls

When an outgoing call is requested, the Modem Manager selects a free modem, or queues the call until a modem becomes free. When a modem is free, the call is dialed. The selected modem may be on a different PC than that requesting the call. The Modem Manager sets up transparent data paths between the modem and the requestor. In the event that the Modem Manager fails to complete the connection, it can retry the attempt using an alternative modem or modems, if they are available.

Incoming Calls

When an incoming call is received by one of the pool modems, the Modem Manager passes the initial data to objects that have previously registered an interest in incoming calls (discriminator modules).

• If an object accepts the offered call, then the Modem Manager sets up transparent data paths between the modem and the recipient.
• If no one accepts the call, then the Modem Manager returns the call to the operating system to allow other applications the opportunity to take the call.

This incoming discrimination can also function with incoming audio calls.

At any time there are three logical PCs involved in a call:

• The caller or receiver.
• The Modem Manager server.
• The owner of the physical modem.

Depending upon the configuration of your system, the roles of these three logical PCs may be played out on one, two, or three physical PCs.