Echelon LNS - Manual (Page 44)

LNS Programmer's Guide 30
the network device represented by the object. This is described in more detail later in the
chapter.
LNS leverages Microsoft’s COM and ActiveX technologies, the Windows standard for
component-based software, to simplify the development of network applications for
Windows hosts. Using LNS, developers are free to take advantage of the support for
ActiveX and COM components built into Windows development tools.
COM interfaces are 32-bit, language-independent programmable objects that can be used
with a variety of development tools, such as Microsoft Visual Basic and Visual C++.
These tools make COM interface calls and property assignments look like native
language calls and assignments. LNS applications can therefore be implemented without
knowing the underlying ActiveX and COM mechanisms.
LNS Components
The LNS Programming Model is comprised of the following major components. These
components are described in the following sections.
• LNS Databases and the LNS Server
• LNS Object Server
• Network Service Devices
• Network Interfaces
LNS Databases and the LNS Server
LNS uses two types of databases to store and maintain the configurations of your
L
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networks: the LNS global database, and a set of LNS network databases.
These are high-performance disk-based databases with in-memory caching to optimize
repeated access to data.
The PC containing the LNS global database acts as the LNS Server. The location of the
global database is maintained in the Windows Registry, and can be accessed by reading
the
DatabasePath
property of the LNS ActiveX Object Server Control. By default, the
global database is stored in the ObjectServer\GlobalDb subfolder of the L ON W ORKS
folder. The location of the global database will be set when LNS is installed and should
never be changed, as LNS applications must access the same global database if they are
to interoperate.
The global database contains the Networks collection, which is the group of L
ON
W
ORKS
networks that are being managed with the LNS Server. Each of these networks has its
own network database. The network database contains the network and device
configuration information for that particular L
ON W ORKS network. The location of each
network database is specified when a network is created, and stored in the global
database. Each LNS network database also contains extension records, which are user-
defined records for storing application data. For more information on this, see the online
help for the Extensions object in the LNS Object Server Reference help file.
LNS applications can run as local client applications, meaning that they run on the same
PC as the LNS Server and the global database. Or, they can run as remote client
applications, meaning that they do not run on the same PC as the LNS Server. This is
shown in Figure 3.2.