介绍两种收集来的本地DNS解析的方式

- (NSArray*)DNSBySystem:(NSString *)dominName{    Boolean result = '\0',bResolved;    CFHostRef hostRef;    CFArrayRef addresses = NULL;    NSString *finalString = nil;    char tempChar[1000];    NSMutableArray *ipResults = [NSMutableArray arrayWithCapacity:10];    strcpy(tempChar,(char *)[dominName UTF8String]);    CFStringRef hostNameRef = CFStringCreateWithCString(kCFAllocatorDefault, tempChar, kCFStringEncodingASCII);    hostRef = CFHostCreateWithName(kCFAllocatorDefault, hostNameRef);    if (hostRef) {        result = CFHostStartInfoResolution(hostRef, kCFHostAddresses, NULL);        if (result == TRUE) {            addresses = CFHostGetAddressing(hostRef, &result);        }    }    bResolved = result == TRUE ? true : false;        if(bResolved)    {        struct sockaddr_in* remoteAddr;        for(int i = 0; i < CFArrayGetCount(addresses); i++)        {            CFDataRef saData = (CFDataRef)CFArrayGetValueAtIndex(addresses, i);            remoteAddr = (struct sockaddr_in*)CFDataGetBytePtr(saData);            if(remoteAddr != NULL)            {                //DNS解析结果cpy到char数组里                char ip[16];                strcpy(ip, inet_ntoa(remoteAddr->sin_addr));                finalString = [NSString stringWithCString:ip encoding:NSUTF8StringEncoding];                [ipResults addObject:finalString];            }        }    }    CFRelease(hostNameRef);    CFRelease(hostRef);    return ipResults;}复制代码

上面这种方法在IPv6环境下解析有点问题，IPv4下无问题。下面这种方法两种环境下都适用

- (NSArray *)dnsByLocal:(NSString *)domain {    if (domain.length == 0) {        return nil;    }    struct addrinfo hints;    memset(&hints, 0, sizeof(hints));    hints.ai_family = PF_INET;    hints.ai_protocol = IPPROTO_TCP;    struct addrinfo *addrs, *addr;        int getResult = getaddrinfo([domain UTF8String], NULL, &hints, &addrs);    if (getResult || addrs == nil) {        NSLog(@"Warn: DNS with domain:%@ failed:%d", domain, getResult);        return nil;    }    addr = addrs;    NSMutableArray *result = [NSMutableArray array];    for (addr = addrs; addr; addr = addr->ai_next) {        char host[NI_MAXHOST];        memset(host, 0, NI_MAXHOST);        getnameinfo(addr->ai_addr, addr->ai_addrlen, host, sizeof(host), NULL, 0, NI_NUMERICHOST);        if (strlen(host) != 0) {            [result addObject:[NSString stringWithUTF8String:host]];        }    }    freeaddrinfo(addrs);    NSLog(@"Info: DNS with domain:%@ -> %@", domain, result);    return result;}复制代码