Hi Sara,
Thanks for getting back to me, I worked with the tutorial and it works fine as it is intended to, but when I start communicating with my esp8266. I get the same problem, I have attached a link with a snapshot of the issue I have. My Arduino serial output and node-red and code are taken from the book for your reference. 
https://drive.google.com/file/d/1id7rZAiYyer60BZ6FiXZapFxlK1grfTx/view?usp=sharing