Echelon OpenLDV User Manual download pdf (Page 142)

134 Extending xDriver

these fields should only be updated from the UpdateLookup function. The

database configuration interface that you create must update these fields in a

guaranteed, safe manner. For more information about how the lookup extension

component handles authentication key changes, see Authentication Key Handling

on page 111.

After the SCO has been filled in and the UpdateLookup() method has been

called (if necessary), the OpenLDV application that launched the lookup

extension component can open the network, and perform whatever network

operations are desired.

The destructor, Finalize function, is called last. It is used to close the database

connection if it is still open. If an instance has not been defined, the destructor is

called following DownlinkLookup function. If an instance has been defined,

the destructor is called when the last object using the instance closes.

xDriver Profiles

After you finish programming your custom lookup extension component, you can

create an xDriver profile to use it. An xDriver profile represents a set of

configuration parameters that determines how xDriver manages sessions,

including:

• The port that xDriver uses to listen for uplink connection requests

• The port that xDriver uses to initiate downlink connections

• The lookup extension to use to look up RNIs

• A flag to enable xDriver automatic reconnection

If you enable automatic reconnection, xDriver attempts to reconnect any uplink

or downlink session that is broken as a result of some unexpected connection

failure. With automatic reconnection enabled, you can configure xDriver to

attempt reconnection as soon as it detects a failed session. xDriver attempts

reconnection until the session has been successfully reestablished or until a time

period that you define has expired.

The profile to be used for each session is determined on a session-by-session

basis. For a downlink session, the profile to use is specified in the network

interface name of the RNI. The network interface name for an RNI using

xDriver must use the following naming convention:

X.[Profile Name].[Downlink Lookup Key]

where [Profile Name] represents the name of the profile to use for the session and

[Downlink Lookup Key] represents the downlink lookup key that was assigned to

the RNI when it was added to the xDriver database. For sample programs that

use this naming convention, see Downlink Sample Applications on page 138.

For an uplink session, the request for connection arrives on a specific TCP port.

The xDriver profile using that port as its listener port handles the uplink session.

You can set the listener port that a profile should use with the OpenLDV xDriver

Profile Editor.

There are two ways to install profiles when you distribute your application:

• Install the profiles with permanent Registry entries that will never be

uninstalled or overwritten. This method has the disadvantage that re-

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