Echelon OpenLDV - Manual (Page 113)

OpenLDV Programmer’s Guide 105
identification message from the RNI that requested the uplink session.
From this message, the Connection Broker obtains the uplink lookup key
for the RNI. The SCO for the session is then initialized, and the uplink
lookup key is inserted into the SCO.
For RNIs that use a modem to connect to the LNS Server, you can create
a listener application that uses the Windows Remote Access Service
(RAS) to handle the modem communications with the RNI. This
application then passes the uplink request to the Connection Broker. See
the Microsoft Developer Network (MSDN) library for more information
about Windows RAS programming.
2. 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 page 108. For sample programs that initiate
downlink xDriver sessions, see Chapter 7, LNS Programming with
xDriver, on page 137.
3. If the authentication flag indicates that authentication is enabled for the
session, the xDriver protocol engine uses the authentication keys in the
SCO to verify the identity of the request for connection. The xDriver
protocol engine handles authentication, and all other message
handshaking, when a connection between an LNS Server and an RNI is
initiated.
If authentication fails, the connection is terminated. If authentication
succeeds, the following steps occur. For more information about
authentication, see Authentication Key Handling on page 111.
4. The Connection Broker service creates an entry for the network that
requested the uplink session in the System.NetworkInterfaces
collection.
5. The Connection Broker service sends a message to the OpenLDV
application.
6. If the OpenLDV application is an LNS Server, the LNS Server causes the
OnIncomingSessionEvent event to be fired in an LNS application that
is programmed to listen for and manage uplink session requests. The
application can then accept or reject the session using the
AcceptIncomingSession method. These methods are available within
LNS for use with xDriver. For more information, see Appendix B, LNS
Methods and Events for xDriver, on page 153.
If the application rejects the session, the session is terminated
immediately. If it accepts the session, the connection is established, and
packets are exchanged in both directions. The LNS application must be
running, and must have registered for the uplink session listener event,
to receive the uplink session notification. For a sample application that
listens for and manages uplink sessions, see Uplink Sample Application