https://blog.gongquiz.com/2021/12/02/%eb%8b%a4%ec%9d%8c-tcp-%ed%8c%a8%ed%82%b7%ec%9d%98-%ed%94%8c%eb%9e%98%ea%b7%b8-%ec%a4%91%ec%97%90%ec%84%9c-%ec%97%b0%ea%b2%b0%ec%9d%b4-%ec%a0%95%ec%83%81%ec%a0%81%ec%9c%bc%eb%a1%9c-%eb%81%9d%eb%82%a8/