Echelon LNS - Manual (Page 110)

LNS Programmer's Guide 96
each method. For more information on this, see System Management Mode
Considerations on page 97.
Discovering When Devices are Detached or Replaced
Your LNS application can check if devices are still present in the network by periodically
attempting to communicate with them. One way to do so is to invoke the Test() method
on each AppDevice you need to check on. The Test() method verifies that the device is
present on the network, that it is properly configured, and that no other devices on the
network are using the network address assigned to the device.
If the Test() method returns lcaTestResultComm as the test status, it may indicate
that the device has been detached from the network. A device might be detected as
detached for several reasons, some of which will indicate the need for repair rather than
a removal or replacement. For example, the device might be detected as missing because
it has been detached from the network for physical maintenance, or because it has been
powered off. In this case, the best response from the application would be to prompt the
user to inspect the physical hardware. If the device has been physically removed from the
system, and does not need to be replaced, the application should perform a logical device
removal to keep the LNS database synchronized with the physical removal, or it can
simply decommission the device if a replacement is expected in the future. For more
information on this, see Removing Devices on page 137.
The Test() method can return many possible values (e.g. lcaTestResultCommSnode,
lcaTestResultMismatchDomain, etc.) as the test status if the device being tested is
not properly configured. This could happen because of faulty device hardware design.
You can try to correct these errors by re-commissioning the device with the
Commission() or CommissionEx() methods. Consult the LNS Object Server Reference
help file for more information on the Test() method.
The Test() method is not the only way to determine when devices have been detached
from the network. You can use the BeginAttachmentEvent() method to subscribe your
application to the OnAttachment event. Once you register for this event, the LNS Object
Server will periodically ping the devices on your network, and fire the event if any are
missing. This is much more efficient than the Test() method, but not as
comprehensive. You can determine the interval at which each device is pinged by writing
to the AppDevice object’s PingClass property. You can set this property to any of the
following values:
lcaPingClassMobile Check detachment frequently (1 minute by
default).
lcaPingClassTemporary Check detachment less frequently (2 minutes
by default).
lcaPingClassStationary Check detachment occasionally (15 minutes by
default).
lcaPingClassPermanent Never check.
You can set the ping frequency for each of these ping classes by writing to the System
object's PingInterval property. The default ping rate is once every 15 minutes, unless
the System object’s InstallOptions property is set to lcaSharedMedia, in which case
pinging will be disabled.