Overview

We saw in the last chapter that all applications access the services of DCOM as well as the components themselves using the same class and interface-based approach. In other words, all the services are accessed via a common object-based interface or "API." The API is implemented in the COM Library.

In this chapter we explore this concept further by looking at the concept of the client at the two ways in which interfaces can be used, via the use of stubs and VTables or using Type Libraries. We will also be briefly covering the IDispatch interface.

Application

Microsoft uses the term application in a generic way to mean either a client or a server or a collection of clients and servers. All applications (clients or servers) have some set responsibilities whether they are clients or servers. On application startup they must:

Figure 5.1: The COM interface

On application shutdown they must "uninitialize" the COM library.

All applications must also perform their own memory management during processing, and we will see how DCOM provides commands to help in this in a later chapter.

Client

A client is any application requesting for an object to be instantiated via DCOM/COM; as such the term "client" really describes a role. Clients are responsible for:

Server

A server is a...