Server (and Handler) Responsibilities

To meet the COM standard for component instantiation, a server must provide the following, regardless of whether it's a DLL or an EXE:

• Registry entries that associate the server module with the CLSID. This can be optionally provided through self-registration and can include entries through which the server indicates that it should be used to emulate another server.
• An implementation of a class factory object that supports IClassFactory through which COM asks the server to create the root object in the component. This class factory can support IClassFactory2 instead if it wants to control object creation through licensing.
• A mechanism through which COM can access the server's class factory.
• An unloading mechanism through which the server that is no longer serving any objects can be removed from memory.

Although all servers follow the generic structure shown in Figure 5-3 on the next page, the exact implementation of each of these requirements differs for DLLs and EXEs, regardless of whether those modules exist on the same machine or on a different machine from the client. The details of these requirements apply to remote servers just as they do to in-process and local servers. In addition, an object handler is structurally equivalent to a full-blown DLL server, so everything described here for DLLs also applies to handlers. The only difference between a handler and a full server is the extent of the implementation found in that component.

Figure 5-3.

The generic structure of a server module.