Echelon OpenLDV User Manual download pdf (Page 150)

142 LNS Programming with xDriver

Private Sub CloseNetB_Click()

OpenNetB.Enabled = True

CloseNetB.Enabled = False

g_SystemB.Close

g_NetworkB.Close

End Sub

'Private Sub Form_Load() is called when the form Load event occurs.

Private Sub Form_Load()

g_cOS.RemoteFlag = False 'Set the application access mode to local.

g_cOS.SingleUserMode = False 'Allow multiple applications to access LNS

'server.

g_cOS.Open 'Open the Object Server.

CloseNetA.Enabled = False 'Disable the Close Network buttons, so that a

CloseNetB.Enabled = False 'cannot try to close a network before it has

'been opened.

End Sub

Private Sub Form_Unload(Cancel As Integer)

G_cOS.Close 'Close the object server.

End Sub

Uplink Sample Application

The following Visual Basic sample program is a listener application that

manages uplink sessions between the LNS Server and multiple RNIs. This

application first registers for uplink session event handling, and uses a timer

control to check when uplink session requests are received. When the timer

control discovers that a request for uplink session has been received, the

application opens the network that has requested the session. Thus, the

application can run without user interaction, other than starting and stopping

the application.

This sample program uses several events and methods within the LNS Server for

use with xDriver. For additional information, see Appendix B, LNS Methods and

Events for xDriver, on page 153.

In the Form_Initialize() function, the application registers for uplink session

event handling by calling the BeginIncomingSessionEvent function. The

OnIncomingSessionEvent event is fired each time an uplink session event is

received. This event handler is called m_cOS_OnIncomingSessionEvent in

this application, because the instance of the LNS Server for this application is

named m_cOS.

The uplink session is accepted or rejected by calling the

AcceptIncomingSession method from the

m_cOS_OnIncomingSessionEvent event handler. If the session is accepted,

the name of the network that requested the uplink session is stored in a global

variable. This variable is used to open the network. This application also sets

the DoPostponeUpdates flag to True when it calls the

AcceptIncomingSession method. All monitor-point updates are then withheld

until the ReleasePendingUpdates method is called. Your application can

receive the monitor-point update event that caused the uplink session request.

The network should not be opened from the event handler, so the

OnIncomingSession event sets a flag to True to indicate that an uplink session

request has been received. This flag causes the StartButton_Click() function to

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