:: Multilayer Structure Connection Mode Selection Analysis ::
Borland's Midas allows us to build a powerful multi-layer distributed database system with Delphi, Midas offers a wide variety of client programs and intermediate-level connection methods such as Sockect, DCOM, CORBA, etc., so many ways, How should we choose when developing multi-layer systems, let me briefly introduce these links. Socket:
Socke is undoubtedly the easiest way to configure. And Socket uses only one port for communication, so if the administrator will be more happy to accept Socket because of the DCOM of the firewall because the DCOM configured is relatively troublesome. On the machine where the intermediate layer is installed, you can establish a socket connection with the client as long as you run SCKTSRVR.exe. But Socket does not support Early-binding
COM and DCOM:
COM / DCOM provides a core NTLM security and verification mechanism. Inside COM / DCOM we can easily use Early-Binding, callback mechanisms (Callback) and connectivity mechanisms (CONNECTIONPOINTS). However, its unfavorable factor is to configure the client's DCOM and let DCOM are quite troubles with firewall (firewall).
MTS:
The MTS can provide database linkage, transaction support, easy distribution, etc., which combines COM and MTS on it based on COM (Windows2000 has provided this service). The disadvantage of MTS is that transaction support for processing multi-user applications using BDE is very weak. Of course, ADO is not here.
CORBA:
Corba is a cross-platform open standard (especially in many Java applications because they are all cross-platform products), through Visibroker (very famous ORB system), the configuration is more convenient than DCOM. Borland's IDL2PAS product is made to make us more written Delphi's client to access CORBA components. Corba itself load balancing, naming services, and event services allow developers to build a more stable and extended distributed system. The disadvantage is that we cannot use early wrap in the development of CORBA systems; in order to support the Cobra client, additional files need to distribute additional files such as borlndmm.dll, cp3245mt.dll, midas.dll, orb_br.dll, orbpas50.dll; Delphi is not Can use all Visibroker features, such as Oad and GateKeeper running in service
