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DCOM implementation distributed application (six)
Cross-platform interoperability standard
From another aspect, DCOM defines cross-platform services (or abstraction) to object-oriented distributed computing, including connection components, creating components, components, and methods of activating components, and a security frame. In addition to these, DCOM only uses services on each platform to complete multi-threaded and concurrent control, user interface, file system interactions, non-DCOM network interactions, and actual security modules.
Use most DCE RPC
The DCOM line protocol is based on DCE RPC, so it is easy to implement a DCOM system on a platform that can use DCE RPC. DCE RPC defines that the data structure and parameter in the memory are confirmed to be a network package. Its network data representation (NDR) is unrelated to the platform and provides a wide range of available data types. COM and DCOM also borrowed the concept of the GUIDS of DCE RPC. DCE RPC provides conflict freedom and non-controlled objects and interface naming mechanisms, which constitutes a COM robust version of the foundation. The pluggable security module of DCOM can achieve seamless binding with DCE-based security environments. Now Windows NT 4.0 can be used as a platform that supports ORPC-Enhanced DCE RPC (DCOM) and only a gateway between platforms supported by standard DCE RPC. This is very useful for many existing DCE RPC applications on a comprehensive platform, and these applications can be converted into applications that can utilize many excellent features of DCOM.
Seamless integration with other Internet protocols
The INTERNET's kernel is a global, non-centralized management and shared TCP / IP-based network. It makes global connectivity. It causes the Internet to attract key applications for many users being a simple, standardized page description language (HTML) and a simple text-making download protocol (HTTP). Distributed applications can benefit from the Internet in a variety of different ways.
DCOM on virtual private network
Even at the lowest level, the Global TCP / IP network provides new opportunities for companies to connect to remote sites and personal users. A virtual private network such as Windows NT 4.0 Point Channel Protocol (PPTP) is a way to use the network to secure private information on the Internet. DCOM-based applications can transparently transparently transparently ported to virtual private networks.
Figure 16 DCOM on a private virtual network
DCOM on the Internet
Because DCOM is born is a secure protocol, it can not be packaged on a virtual private network: DCOM applications can easily use global TCP / IP networks. Most companies do not provide direct access to the company's desktop computer via Internet. Almost all exquisite and complex servers are under the protection of firewalls, the firewall is generally composed of a protocol (based port number) and the application level (proxy server) filter. DCOM can work well under these two types of firewalls: DCOM uses a port to initialize the connection and assign a range of ports to actual components that are running on the machine. Apply level agents can be easily created. They can be either a generally applying. The server administrator can also create a DCOM channel via HTTP, which can effectively avoid most of the firewalls now. With these functions, DCOM-based applications can use Internet to establish private connections in the company, and customers outside the company and the private communication of partners, and a large number of public connections to any customers in the world. In every case, DCOM can provide a flexible security mechanism when necessary.
Integrated HTML and distributed calculations
In addition to using Internet only as an inexpensive TCP / IP network, distributed applications can also utilize the advantages of existing standard protocols and formats. For the need for interacting, text or simple graphics information, the HTML page can provide a famous and effective way for users to access the required information. For more complex, structured and interacting information, components can be extended to extend the HTML page to real distributed tasks in a user-friendly, secure, and effective way. Some simple transaction rules can be applied to the client to provide quick feedback. More complex transaction rules can transparently activate components on the DCOM. Because DCOM language independence, these components can be done in any programming language, including C , Java, Visual Basic, or COBOL. Existing components (ActiveX controls) can be incorporated into the client or on server-side customer components written by Visual Basic Script or Java Script. Regardless of whether developers use HTML components to enrich distributed applications, or use distributed computational factors to enrich the HTML-based "application", DCOM can provide the necessary components to combine them.
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