https://blog.gongquiz.com/2022/06/24/%eb%8b%a4%ec%9d%8c-%ec%a4%91-rs-232c%ec%99%80-%ea%b0%80%ec%9e%a5-%ea%b4%80%eb%a0%a8%ec%9d%b4-%ec%9e%88%eb%8a%94-%ea%b2%83%ec%9d%80-%ec%a0%95%eb%b3%b4%ec%b2%98%eb%a6%ac%ea%b8%b0%eb%8a%a5%ec%82%ac-2/