说明：  设计一个DNS服务器程序，读入“IP地址-域名”对照表，当客户端查询域名对应的IP地址时，用域名检索该对照表，有三种可能检索结果： 检索结果：ip地址0.0.0.0，则向客户端返回“域名不存在”的报错消息（不良网站拦截功能） 检索结果：普通IP地址，则向客户端返回该地址（服务器功能） 表中未检到该域名，则向因特网DNS服务器发出查询，并将结果返给客户端（中继功能） 考虑多个计算机上的客户端会同时查询，需要进行消息ID的转换
(Design a DNS server program that reads the "IP address- domain name" table, when the client queries the corresponding IP address, the domain name to retrieve the table, there are three possible search results: Search Results: ip address 0.0.0.0, then returned to the client "domain name does not exist" error message (bad site blocking features) Search Results: Normal IP address, the address is returned to the client (server function) Table did not check into this domain, the DNS server sends queries to the Internet, and the results returned to the client (relay function) Consider a client on multiple computers simultaneously queries the need for conversion of message ID)