Connecting BBB through Ethernet cable only?


I’m working on the bone script thing and I’d like to connect the BBB with laptop through just ethernet cable, not usb connection (I have charger to power the BBB). Then I need to control the hardware part of the BBB, for example, the lights on/off. One idea from others is using bone script as server on BBB, then on laptop we can control the hardware using the function bone script provides. But I’m not sure what should I do now, as I can not connect to the BBB, if I don’t know the ip address of it. Any idea?

I’m using the ubuntu on my laptop and BBB uses the default Angstrom.

Thanks a lot!