IPv6、IPv4中的四个地址结构:sockaddr、sockaddr_in、sockaddr_in6、addrinfo的对比
structsockaddr{unsignedshortsa_family;/*addressfamily,AF_xxx*/charsa_data[14];/*14bytesofprotocoladdress*/};structsockaddr_in{shortintsin_family;/*AddressfamilyAF_INET*/unsignedshortintsin_port;/*Port