// Create a NPC
final npc = NPC();
npc.send = (message) async{
// send message
};//call when message received:
await npc.receive(message);// register handle
npc.on('ping', (param, cancelable, notify)=>'pong');// emit
await npc.emit('say', 'hello');// deliver
final r = await npc.deliver('download', param: '/path', onNotify: (param){
});