gethostbyname替代getaddrinfo

2015/05/19

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：
[cpp]struct hostent* FAR gethostbyname(
_In_ const char *name
);[/cpp]

之前使用gethostbyname 很简单，类似这样：
[cpp]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));
}
}
}[/cpp]

现在得用getaddrinfo，其原型如下：
[cpp]int WSAAPI getaddrinfo(
_In_opt_ PCSTR pNodeName,
_In_opt_ PCSTR pServiceName,
_In_opt_ const ADDRINFOA *pHints,
_Out_ PADDRINFOA *ppResult
);[/cpp]
得这么用：
[cpp]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;
}
}[/cpp]

转载自：mosir.org

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