I have my iMac and MB pro connected by firewire. I can see the connection in the finderwindow, but can't locate the machines in terminal. Can someone help me?

Also, it seems that whenever I connect to my firewire machine from the finder window (using 'connect as' and typing in the username and password,) I lose the connection when I switch to another window and I'm back to being connected as a 'guest', What's going on and how do I maintain that connection?