This event is fired when client requests an IP address that you offered him before. If you choose to deny client's request for any reason (address is already in use, etc.) Session will be removed from wodDHCPD.Sessions collection and deleted. Before accepting a request, you should set some configuration options that will be sent to the client. Here's an example how to do this:

Private Sub DHCP_Request(ByVal Session As wodDHCPDLibCtl.IDHCPSession)

With Session
.DNSServer = "192.168.1.1"
.BroadcastAddress = "192.168.1.255"
.NetBiosNS = "192.168.1.2" ' Also known as WINS
.SubnetMask = "255.255.255.0"
.Gateway = "192.168.1.1"
.AcceptRequest
End With

End Sub