Windows® Internals, Sixth Edition, Part 1

Microsoft’s COM API lets applications consist of different components, each component being a replaceable, self-contained module. A COM object exports an object-oriented interface to methods for manipulating the data within the object. Because COM objects present well-defined interfaces, developers can implement new objects to extend existing interfaces and dynamically update applications with the new support.

DCOM (Distributed Component Object Model) extends COM by letting an application’s components reside on different computers, which means that applications don’t need to be concerned that one COM object might be on the local computer and another might be across the network. DCOM thus provides location transparency, which simplifies developing distributed applications. DCOM isn’t a self-contained API but relies on RPC to carry out its work.

Message Queuing

Message Queuing is a general-purpose platform for developing distributed applications that take advantage of loosely coupled messaging. Message Queuing is therefore an API and a messaging infrastructure. Its flexibility comes from the fact that its queues serve as message repositories in which senders can queue messages for receivers, and receivers can de-queue the messages at their discretion. Senders and receivers do not need to establish connections to use Message Queuing, nor do they need to be executing at the same time, which allows for disconnected asynchronous message exchange.

A notable feature of Message Queuing is that it is integrated with Microsoft Transaction Server (MTS) and SQL Server, so it can participate in Microsoft Distributed Transaction Coordinator (MS DTC) coordinated transactions. Using MS DTC with Message Queuing allows you to develop reliable transaction functionality for three-tier applications.

UPnP with PnP-X

Universal Plug and Play is an architecture for peer-to-peer network connectivity of intelligent appliances, devices, and control points. It is designed to bring easy-to-use, flexible, standards-based connectivity to ad-hoc, managed, or unmanaged networks, whether these networks are in the home, in small businesses, or attached directly to the Internet. Universal Plug and Play is a distributed, open networking architecture that uses existing TCP/IP and Web technologies to enable seamless proximity networking in addition to control and data transfer among networked devices.

Universal Plug and Play supports zero-configuration, invisible networking, and automatic discovery for a range of device categories from a wide range of vendors. This enables a device to dynamically join a network, obtain an IP address, and convey its capabilities upon request. Then other control points can use the Control Point API with UPnP technology to learn about the presence and capabilities of other devices. A device can leave a network smoothly and automatically when it is no longer in use.

Plug and Play Extensions (PnP-X), shown in Figure 7-18, is an additional component of Windows that allows network-attached devices to integrate with the Plug and Play manager in the kernel. With PnP-X, network-connected devices are shown in the Device Manager like locally attached devices and provide the same installation, management, and behavioral experience as a local device. (For example, installation is performed through the standard Add New Hardware Wizard.)

Figure 7-18. PnP-X implementation

PnP-X uses a virtual network bus driver that uses an IP bus enumerator service (%SystemRoot%\System32\Ipbusenum.dll) to discover PnP-X compatible devices, which include UPnP devices (through the Simple Service Discovery Protocol) and the newer Device Profile for Web Services (DPWS) devices (using the WS-Discovery protocol). The IP bus enumerator reports devices it discovers to the Plug and Play manager, which uses user-mode Plug and Play manager services if needed (such as for driver installation). It’s similar to wireless discovery (like Bluetooth) and unlike wired device discovery (like USB), however, PnP-X enumeration and driver installation must be explicitly requested by a user from the Network Explorer.

Note

DPWS v1.1 became an OASIS standard in June 2009 and has goals similar to those of UPnP, but it is tightly integrated with web services standards and frameworks and allows greater extensibility than UPnP.

Multiple Redirector Support