Echelon OpenLDV - Manual (Page 22)

14 Using the OpenLDV API
Referencing the OpenLDV Component
You can develop applications that use the OpenLDV API with any Windows
application development environment that supports the use of standard Windows
DLL components and (for xDriver Extensions) COM components. Echelon has
tested the OpenLDV software with Microsoft Visual Studio 2008, using the
Microsoft Visual C++ ® , Visual C# ® , and Visual Basic ® components.
To develop an applicatikon with the OpenLDV API, first install the OpenLDV
driver and the OpenLDV SDK. During the installation, the ldv32.h and
ldv32.lib files are copied to the L ON W ORKS \OpenLDV SDK\Include and
\OpenLDV SDK\Lib folders.
To develop your OpenLDV application, include the ldv32.h header file in your
application and link it with the ldv32.lib library. See your development
environment’s documentation for information about linking to external libraries.
End users of your OpenLDV application do not need to install any of the files
included in the OpenLDV SDK; they need only install the OpenLDV driver.
The OpenLDV SDK includes the OpenLDV Developer Example, which uses many
of the functions described in this chapter. To compile and debug the OpenLDV
Developer Example, install Microsoft Visual Studio 2008 (or later), with the
Microsoft Visual C++ component. The example application is available from the
Examples & Tutorials folder in the Echelon OpenLDV 4.0 SDK program
folder; it is also installed as a ZIP file to the \LonWorks\OpenLDV
SDK\SourceArchive folder. The OpenLDV Developer Example contains
numerous helpful comments. See Chapter 4, The OpenLDV Developer Example,
on page 89, for a description of the architecture of the OpenLDV Developer
Example and of the different classes that it contains.
Using Multiple Threads or Multiple Processes
The OpenLDV software supports communication with multiple network
interfaces at the same time, with the following restrictions:
1. A single process can access multiple network interfaces simultaneously.
However, a single process should access a network interface with at most
one writer thread and one reader thread. You must program your
application to enforce this restriction, because it is not enforced by the
OpenLDV software. See the OpenLDV Developer Example for a
demonstration of the proper use of separate reader and writer threads.
2. Multiple processes cannot access the same network interface
simultaneously. Attempts to access the same network interface by more
than one process result in the LDVX_ACCESS_DENIED failure code
from the ldv_open() functions.
3. The SmartServer and i.LON network interfaces allow a single session at
a time. If you attempt to open such a network interface while another
session is active (usually from another computer), the call to ldv_open()
might initially appear to have succeeded (the connection is established in
the background). However, when you call ldv_read() or ldv_write() to
read or write a message to the network interface, the functions return the
LDVX_READ_FAILED or LDVX_WRITE_FAILED return codes,
which indicate that the session has failed. See ldv_open() on page 24 for
more information.