As you saw in Chapter 1, the backbone of COM's distributed infrastructure is based on an interprocess mechanism called the Remote Procedure Call (RPC). This chapter gives you some background on RPC and the process of remote activation. It also covers issues associated with the life cycle of COM objects in a distributed environment.
Security is an important concern in a distributed application. Without a robust security model, COM would be worthless to enterprise developers. This chapter describes how COM creates abstractions on top of the Win32 security model to provide secure access to distributed objects. One of the best things about COM security is that it can be used in either a declarative or a programmatic manner. As a Microsoft Visual Basic programmer, you have minimal control over the programmatic side. However, you can use declarative security to make sure that only authenticated and authorized users can access your distributed application.
This chapter describes how to configure servers and client computers when you deploy an application with Distributed COM. It introduces a new Registry key called the AppID, and it shows you how to modify the Registry to track information about the security and server locality of a COM-based application. As you'll see, the AppID plays an important role in both server-side and client-side configuration.
You'll also learn how applications based on Distributed COM worked before the introduction of Microsoft Transaction Server (MTS). You must wait until the next chapter to see how MTS provides a run-time environment for distributed objects. However, it's important for you to understand that MTS is layered on top of the infrastructure of Distributed COM. Everything that MTS does with regard to remote activation, security, and configuration is based on the capabilities of Distributed COM and the RPC layer. To really understand MTS, you must first appreciate what's going on underneath.
Finally, you'll learn about a few significant limitations associated with the initial release of Distributed COM. Certain problems relating to application security and configuration are tricky and expensive to solve. Fortunately, MTS provides a valuable solution to these problems, which is described in Chapter 9.