Echelon OpenLDV User Manual download pdf (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

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