Echelon OpenLDV User Manual download pdf (Page 109)

OpenLDV Programmer’s Guide 101

of the downlink lookup key. Chapter 7, LNS Programming with xDriver, on page

137, provides programming samples that illustrate this behavior.

Figure 14 shows the application flow for a downlink session.

User Application xDriver Manager

Database

Lookup Extension

x.Profile.RNI

Figure 14. Downlink Session

The application flow for a downlink session includes the following steps (see

Figure 14):

1. When the OpenLDV application initiates the connection, the xDriver

manager initializes an SCO for the session, and adds the downlink lookup

key (derived from the network interface name of the RNI) into the SCO.

2. The SCO is then passed to the lookup extension component.

3. The lookup extension component extracts the downlink lookup key from

the SCO, and uses it to access the database record for the specified RNI.

The lookup extension component then retrieves additional information

from the database (such as authentication flag, authentication keys, and

IP address and port number of the RNI) to fill in the SCO with the

information required to establish the connection.

For more information about the SCO and the information it stores, see

Session Control Object on 108. For sample programs that initiate

downlink xDriver sessions, see Chapter 7, LNS Programming with

xDriver, on page 137.

4. The connection is established and the authentication key is used to

validate the connection, if authentication is enabled.

5. If the authentication is successful, packets are exchanged in both

directions. For more information about authentication, see

Authentication Key Handling on page 111.

6. The OpenLDV application performs any required network operations.

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Echelon OpenLDV User Manual Page 109