网络编程 getaddrinfo 函数

解析网址，返回ip地址。

例子：

#include <iostream> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h>//结构体addrinfo, in_addr #include <netinet/in.h> #include <arpa/inet.h>  using namespace std;  int main(){   char* hostname = "www.cnblogs.com";//博客园的网址，返回实际ip地址   addrinfo hints, *res;   in_addr addr;   int err;    memset(&hints, 0, sizeof(addrinfo));   hints.ai_socktype = sock_stream;   hints.ai_family = af_inet;    if((err = getaddrinfo(hostname, null, &hints, &res)) != 0){     printf("error %d : %sn", err, gai_strerror(err));     return 1;   }   addr.s_addr = ((sockaddr_in*)(res->ai_addr))->sin_addr.s_addr;   printf("ip addresss: %sn", inet_ntoa(addr));//博客园的网址，返回实际ip地址      freeaddrinfo(res);    return 0; }