https://blog.gongquiz.com/2023/02/28/rs-232c-%ed%86%b5%ec%8b%a0%eb%b0%a9%ec%8b%9d%ec%9d%98-%ec%a0%9c%ec%a0%95%ea%b8%b0%ea%b4%80%ec%9d%80-%ec%a0%95%eb%b3%b4%ed%86%b5%ec%8b%a0%ea%b8%b0%ec%82%ac-2014%eb%85%84-5%ec%9b%94-31%ec%9d%bc/