The Microsoft .NET Framework provides a rich alternative to the Distributed COM (DCOM) protocol in the form of XML Web services provided by ASP.NET. XML WCF and SOAP Web services allow businesses to distribute their application services to a broader audience than is otherwise possible with DCOM.
DCOM enabled software developers to create applications that span multiple machine, network, and location boundaries, allowing scalability and ease-of-distribution across multiple tiers. Although additional complexity was introduced into the development effort, most of the benefits provided by DCOM (e.g., location independence, security and scalability) were realized to varying degrees. OPC is probably now one of the most widely used implementations of DCOM in industry.
DCOM Security and Firewall Issues - DCOM dynamically allocates one port per process. You need to decide how many ports you want to allocate to DCOM processes, which is equivalent to the number of simultaneous DCOM processes through the firewall. This causes problems for digital security, as applications change all the time which can cause ports to be left open or communication problems when ports are closed. The configuration of applications is usually done by different teams, which adds to the complexity.
DCOM versus Web Services - As the Internet evolves, the nature and scope of distributed applications must change to meet the underlying business needs. Businesses must integrate their applications with those that reside on heterogeneous platforms, and those that are built and deployed with varying programming models. Additionally, businesses need to communicate and expose their services to global clients and partners.
To address these needs, XML Web services were introduced as part of ASP.NET, which is part of the .NET Framework. Web services are based on open Internet standards, such as HTTP, XML, and SOAP. Using these open standards, Web services deliver application functionality across the Web to any type of client, on any platform.