Echelon OpenLDV - Manual (Page 172)

164 Custom Lookup Extension Component Programming
ILdvxLookup Interface
The lookup interface is the primary interface implemented by an xDriver lookup
extension component. It defines the methods that are used to look up session
parameters in your xDriver database.
DownlinkLookup Method
Applies to: xDriver Lookup Extension Component
This method is called by xDriver when a downlink session is initiated. It is
passed a pointer to the xDriver Session Control Object (SCO) for the session. The
SCO contains the downlink lookup key to be looked up. This lookup key comes
from the network interface name of the RNI being opened. For example, in the
"X.Custom.Location-123" NetworkInterface name, the downlink key is "Location-
123".
It is the responsibility of the xDriver lookup extension to extract the downlink
lookup key from the SCO, use it to access its xDriver database, and retrieve the
authentication and TCP parameters to be used by the rest of the xDriver
framework. Then, the lookup extension component must fill in the corresponding
fields of the SCO, including the Authentication Flag, Current Authentication
Key, Next Authentication Key, Additional Downlink Packet Header (optional),
Additional Downlink Packet Trailer (optional), Encryption Type, Remote TCP
Address, and Remote TCP Port. This information is used by xDriver to complete
the session establishment.
The ILdvxSCO interface provides methods that you can use to obtain the
downlink lookup key and fill in the SCO fields. For more information, see
ILdvxSCO Interface on page 166.
Syntax
C++ STDMETHOD(DownlinkLookup)(ILdvxSCO * xSCO)
Visual Basic Sub DownlinkLookup(ByVal xSCO As LdvxLib.ILdvxSCO)
Table 45. DownlinkLookup Parameters
Parameter Description
xSCO Pointer to the SCO object that contains the downlink key to be looked
up. The DownlinkLookup implementation should fill the required
fields into the SCO.
Returns
Standard xDriver LdvxResult (HRESULT) describing the result of the call. The
result is typically LDVX_S_OK (see LdvxResult). If the specified downlink key
is not recognized, the lookup extension component must return the error code