项目需要从域名解析地址，但是编译的时候提示gethostbyname error,百度了一下，这才发现，原来用了N年的gethostbyname 已经是obsolete 的函数了，都标记成DEPRECATED 了，无论是windows 下还是linux 下都建议使用getaddrinfo 来替代它。很好的总结经验：

gethostbyname函数的原型如下：

struct hostent* FAR gethostbyname(
  _In_  const char *name
);

之前使用gethostbyname 很简单，类似这样：

struct hostent *remoteHost;
struct in_addr addr;

if ( ( remoteHost = gethostbyname( hostname ) ) == NULL ){
    xxxx;
}
else{
    if (remoteHost->h_addrtype == AF_INET)
    {
        while (remoteHost->h_addr_list[i] != 0) {
            addr.s_addr = *(u_long *) remoteHost->h_addr_list[i++];
            printf("\tIP Address #%d: %s\n", i, inet_ntoa(addr));
        }
    }
}

现在得用getaddrinfo，其原型如下：

int WSAAPI getaddrinfo(
  _In_opt_  PCSTR pNodeName,
  _In_opt_  PCSTR pServiceName,
  _In_opt_  const ADDRINFOA *pHints,
  _Out_     PADDRINFOA *ppResult
);

得这么用：

struct addrinfo *result = NULL;
struct addrinfo *ptr = NULL;
struct addrinfo hints;

ZeroMemory( &hints, sizeof(hints) );
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;

dwRetval = getaddrinfo(hostname, 0, &hints, &result);
if ( dwRetval != 0 ) {
    xxxx;
}
else{
for(ptr=result; ptr != NULL ;ptr=ptr->ai_next) {

    printf("getaddrinfo response %d\n", i++);
    printf("\tFlags: 0x%x\n", ptr->ai_flags);
    printf("\tFamily: ");
    switch (ptr->ai_family) {
        case AF_UNSPEC:
            printf("Unspecified\n");
            break;
        case AF_INET:
            printf("AF_INET (IPv4)\n");
            sockaddr_ipv4 = (struct sockaddr_in *) ptr->ai_addr;
            printf("\tIPv4 address %s\n",
                inet_ntoa(sockaddr_ipv4->sin_addr) );
            break;
        case AF_INET6:
            printf("AF_INET6 (IPv6)\n");
            // the InetNtop function is available on Windows Vista and later
            // sockaddr_ipv6 = (struct sockaddr_in6 *) ptr->ai_addr;
            // printf("\tIPv6 address %s\n",
            //    InetNtop(AF_INET6, &sockaddr_ipv6->sin6_addr, ipstringbuffer, 46) );

            // We use WSAAddressToString since it is supported on Windows XP and later
            sockaddr_ip = (LPSOCKADDR) ptr->ai_addr;
            // The buffer length is changed by each call to WSAAddresstoString
            // So we need to set it for each iteration through the loop for safety
            ipbufferlength = 46;
            iRetval = WSAAddressToString(sockaddr_ip, (DWORD) ptr->ai_addrlen, NULL, 
                ipstringbuffer, &ipbufferlength );
            if (iRetval)
                printf("WSAAddressToString failed with %u\n", WSAGetLastError() );
            else    
                printf("\tIPv6 address %s\n", ipstringbuffer);
            break;
        case AF_NETBIOS:
            printf("AF_NETBIOS (NetBIOS)\n");
            break;
        default:
            printf("Other %ld\n", ptr->ai_family);
            break;
    }
}

转载自：mosir.org