It is for analysing the CAN-Bus. So that you can see the sended messages.
On CANcaseXL side I got messages when sending from channel1 to channel2 of the CANcaseXL. So it seems that the fault is on the side of the CAN-Shield.
I only connect them like in the pictures and have used the normal sending example of the library.
So is there maybe something more to consider at CAN-Shield which I forgot?