Thanks for your explanation as it helps me out with my problem.
I still some other issues:
1. How would you get a newer version of IDE?
2. What is the maximum character I could send in 64 bytes read buffer?
3. If I throw out String, what is the substitute?
4. Considering question no.3, is there other way to solve my problem without re-writing the program? Can I limit the character of the data without rewriting the program?
Thank you for advice. However, if I don't use delay, based on your experience, what function should I use to hold the led to light for 5 second? if I use interupts timer,can i use 2 different timers in one arduino?
Is there any other comment? I do appreciate your participation