var port = 0;
var interval = 500; // 500[ms]
arduinode.digitalStreamOn(port, interval, function(err, result){
  if(err) throw err;
  console.log(result);
  // {"msg":"OK", "port":0, "val":1}
});

// data event.
arduinode.on("event", function(data){
  console.log(data);
});