In this chapter, we've introduced DCOM as COM with a longer wire. We looked at DCOM on Windows NT 4.0 and DCOM for Windows 95, and covered how we can obtain the software as well as the installation process. We demonstrated how ordinary COM objects can be made to interact over the network with simple registry changes.
Lifting the covers, we took a brief look at how DCOM works. We also covered several changes and additions in APIs that are associated with DCOM. To satisfy situations where we may need to justify DCOM, we provided a top 10 of reasons for deploying DCOM.
Not all is rosy, though. DCOM had some definite limitations, and we discussed how Microsoft intends to address them.
Distributed component systems are of no use if there's no way to distribute the components' code when necessary. We looked at the automated code download and installation technology provided through the complex CoGetClassObjectFromURL() call. We saw how this technology can help in maintaining an updated version of a component based application. To send the concept home, we've even created a 'downloader' ActiveX control to encapsulate the complex call.
Finally, in the last part of the chapter, we went back to the Aberdeen and Wilshire Calendar control example and step by step showed how to distribute the application over three machines.
All the while, we've avoided the complex issue of security in our network and software setup. This is a very important topic and it's the subject of the next chapter.