https://blog.gongquiz.com/2021/04/21/%eb%84%a4%ed%8a%b8%ec%9b%8c%ed%81%ac-%ec%9e%a5%eb%b9%84%eb%a5%bc-%ea%b4%80%eb%a6%ac-%ea%b0%90%ec%8b%9c%ed%95%98%ea%b8%b0-%ec%9c%84%ed%95%9c-%eb%aa%a9%ec%a0%81%ec%9c%bc%eb%a1%9c-tcp-ip-%ec%83%81/