addressesForHostname

addressesForHostname.m

+ (NSArray *)addressesForHostname:(NSString *)hostname
{
    if (!hostname)
    {
        return nil;
    }
    
    // Get the addresses for the given hostname.
    CFHostRef hostRef = CFHostCreateWithName(kCFAllocatorDefault, (__bridge CFStringRef)hostname);
    BOOL isSuccess = CFHostStartInfoResolution(hostRef, kCFHostAddresses, nil);
    if (!isSuccess)
    {
        CFRelease(hostRef);
        return nil;
    }
    
    CFArrayRef addressesRef = CFHostGetAddressing(hostRef, nil);
    if (!addressesRef)
    {
        CFRelease(hostRef);
        return nil;
    }
    CFRelease(hostRef);
    
    // Convert these addresses into strings.
    char ipAddress[INET6_ADDRSTRLEN];
    NSMutableArray *addresses = [NSMutableArray array];
    CFIndex numAddresses = CFArrayGetCount(addressesRef);
    for (CFIndex currentIndex = 0; currentIndex < numAddresses; currentIndex++)
    {
        struct sockaddr *address = (struct sockaddr *)CFDataGetBytePtr(CFArrayGetValueAtIndex(addressesRef, currentIndex));
        if (!address)
        {
            return nil;
        }
        
        getnameinfo(address, address->sa_len, ipAddress, INET6_ADDRSTRLEN, nil, 0, NI_NUMERICHOST);
        if (!ipAddress)
        {
            return nil;
        }
        [addresses addObject:[NSString stringWithCString:ipAddress encoding:NSASCIIStringEncoding]];
    }
    
    return addresses;
}