addrinfo的结构体

struct addrinfo
{
  int ai_flags;
  int ai_family; //AF_INET,AF_INET6,UNIX etc
  int ai_socktype; //STREAM,DATAGRAM,RAW
  int ai_protocol; //IPPROTO_IP, IPPROTO_IPV4, IPPROTO_IPV6 etc
  size_t ai_addrlen;//length of ai_addr
  char* ai_canonname; //full hostname
  struct sockaddr* ai_addr; //addr of host
  struct addrinfo* ai_next;
}

参数	取值	值	说明
ai_family	AF_INET	2	IPv4
	AF_INET6	23	IPv6
	AF_UNSPEC	0	协议无关
ai_protocol	IPPROTO_IP	0	IP协议
	IPPROTO_IPV4	4	IPv4
	IPPROTO_IPV6	41	IPv6
	IPPROTO_UDP	17	UDP
	IPPROTO_TCP	6	TCP
ai_socktype	SOCK_STREAM	1	流
	SOCK_DGRAM	2	数据报
ai_flags	AI_PASSIVE	1	被动的，用于bind，通常用于server socket
	AI_CANONNAME	2	用于返回主机的规范名称
	AI_NUMERICHOST	4	地址为数字串