Well, I found the answer...
You have to get the Object "HarnessWire" first of all. Now you can get the Node from the Start or End with the Method
HarnessWire.getRoute().getStartPoint(); or
HarnessWire.getRoute().getEndPoint();
Check if it is a Node (and cast it), and from the Node you can get all the Connectors with the method
Node.getAllConnectors();
So the way is:
HarnessWire -> Start/End Node -> Connector