How to get CNAME of a domain in iOS - ios

Question

I would like to resolve a domain and get its CNAME and ip info, like the following:
example.com -> cname.com -> ip address
I searched a lot and know how to get the ip address, e.g. by CFHost. But I still don't know how to get other information, like its CNAME.
Should I do this with CFHost or something else?

Answer 1

You can use below code for your purpose
+ (void) getCNAME {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
DNSServiceRef serviceRef;
DNSServiceErrorType error;
error = DNSServiceQueryRecord(&serviceRef, 0, 0, "apple.com", kDNSServiceType_CNAME,
kDNSServiceClass_IN, queryCallback, NULL);
if (error != kDNSServiceErr_NoError){
NSLog(#"DNS Service error");
}
DNSServiceProcessResult(serviceRef);
DNSServiceRefDeallocate(serviceRef);
});}
static void queryCallback(DNSServiceRef sdRef,
DNSServiceFlags flags,
uint32_t interfaceIndex,
DNSServiceErrorType errorCode,
const char *fullname,
uint16_t rrtype,
uint16_t rrclass,
uint16_t rdlen,
const void *rdata,
uint32_t ttl,
void *context) {
if (errorCode == kDNSServiceErr_NoError && rdlen > 1) {
NSMutableData *txtData = [NSMutableData dataWithCapacity:rdlen];
for (uint16_t i = 1; i < rdlen; i += 256) {
[txtData appendBytes:rdata + i length:MIN(rdlen - i, 255)];
}
NSString *theTXT = [[NSString alloc] initWithBytes:txtData.bytes length:txtData.length encoding:NSASCIIStringEncoding];
NSLog(#"CNAME: %#", theTXT);
}}