Writing a CANopen test utility

How do I listen in (preferably using Java) on a small set of well-defined CANopen messages without a commercial CANopen stack?

From stackoverflow

• There is really nothing special about CANopen in this regard. If you are able to read CAN data from the CAN bus you should be OK. The CAN ID of the messages will identify them, and the interpretation of the data will be given in the data emitting device's documentation.

  It's hard to give a generic answer on how to read the data, because everything depends on your hardware situation. However, before you can listen to any CAN messages, you need a CAN interface for your computer. The CAN interface's documentation will probably tell you how to use it.