call.hangup() finishes current call, "hangs up the phone".
call.hangup(reason, message):
Usually call.hangup() is called without any arguments, resulting in normal ending of call.
If call is ended due to a timeout, for example if no media is received from other end any more then the hangup can be given a reason: call.hangup(408, "Media timeout")
Nothing.
call.hangup() raises event wrtc.onHungUp()