Echelon OpenLDV - Manual (Page 98)

90 The OpenLDV Developer Example
Overview
The OpenLDV Developer Example is an example application that uses the
OpenLDV API. The example application is available from the Examples &
Tutorials folder in the Echelon OpenLDV 4.0 SDK program folder.
The example application is also installed as a ZIP file in the L
ON W ORKS
\OpenLDV SDK\SourceArchive folder on your computer. The ZIP file is
named LdvApiExamplesSource_vn.nn.nnn.ZIP, where the n.nn.nnn
represents the version and build number for the OpenLDV release.
The OpenLDV Developer Example is a simple dialog-based Windows application
written in C++ with Microsoft Foundation Classes (MFC). It is distributed in
Microsoft Visual Studio 2008 project format. The example illustrates how a
Windows application can access the OpenLDV API, and demonstrates a wide
range of simple to complex network operations.
The example application contains comments that should assist you when
reviewing the code. This chapter describes the structure of the example
application and the different classes that it contains.
Common Definitions
The OpenLDV API functions are specified in the ldv32.h header file. The
OpenLDV Developer Example provides additional definitions of constants,
enumerations, and aggregated types in the OpenLDVdefinitions.h header file.
These definitions are used throughout the remainder of the example application.
COpenLDVapi and COpenLDVtrace
The example application implements a COpenLDVapi class to wrap the
OpenLDV API functions. The COpenLDVapi class provides a simple interface
through four methods: Open, Close, Read, and Write.
This class provides thread-safe, synchronized, access to downlink messages
(ldv_write()), and implements a reader thread COpenLDVreader, which reads
uplink messages (ldv_read()) and supplies data to a protected queue. The
COpenLDVapi::Read() function reads that queue, thereby providing
coordinated access to both uplink and downlink messages.
The example application also implements a COpenLDVtrace class. This class
illustrates how an OpenLDV application can provide hooks for debugging or
tracing into the low-level portion of the OpenLDV application. The example
implementation provides a packet dump of all incoming and outgoing packets.
The related header files, OpenLDVapi.h and OpenLDVtrace.h, contain details
about these classes and their usage.
COpenLDVni, Message Pumps, and Message
Dispatchers
The COpenLDVni class implements the core functions of a network interface
API. The functions included in this class are NiInit(), NiSendMsgWait(),