start method
Starts to do either a discover or a broadcast.
Implementation
@override
Future<void> start() {
assert(isReady,
'''$runtimeType should be ready to start in order to call this method.
You must wait until this instance is ready by calling "await $runtimeType.ready".
If you have previously called "$runtimeType.stop()" on this instance, you have to create a new instance of this class.''');
return channel.invokeMethod('$_classType.start', toJson());
}