How to perform DNS query on iOS
i want to perform some DNS queries e.g. to get IP records against a specific domain name, i am looking for a preferred way or some useful snippet for this on iOS 3.2+ SDK. thanx in advance
part from other snippets i found this code
Boolean result;
CFHostRef hostRef;
NSArray *addresses;
NSString *hostname = @"apple.com";
hostRef = CFHostCreateWithName(kCFAllocatorDefault, (CFStringRef)hostname);
if (hostRef) {
result = CFHostStartInfoResolution(hostRef, kCFHostAddresses, NULL); // pass an error instead of NULL here to find out why it failed
if (result == TRUE) {
addresses = (NSArray*)CFHostGetAddressing(hostRef, &result);
}
}
if (result == TRUE) {
[addresses enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSString *strDNS = [NSString stringWithUTF8String:inet_ntoa(*((struct in_addr *)obj))];
NSLog(@"Resolved %d->%@", idx, st开发者_JS百科rDNS);
}];
} else {
NSLog(@"Not resolved");
}
but this is producing same IP for every host Resolved 0->220.120.64.1 any help??
Figured out a change in this snippet makes it working
if (result == TRUE) {
NSMutableArray *tempDNS = [[NSMutableArray alloc] init];
for(int i = 0; i < CFArrayGetCount(addresses); i++){
struct sockaddr_in* remoteAddr;
CFDataRef saData = (CFDataRef)CFArrayGetValueAtIndex(addresses, i);
remoteAddr = (struct sockaddr_in*)CFDataGetBytePtr(saData);
if(remoteAddr != NULL){
// Extract the ip address
//const char *strIP41 = inet_ntoa(remoteAddr->sin_addr);
NSString *strDNS =[NSString stringWithCString:inet_ntoa(remoteAddr->sin_addr) encoding:NSASCIIStringEncoding];
NSLog(@"RESOLVED %d:<%@>", i, strDNS);
[tempDNS addObject:strDNS];
}
}
}
Bros there is a lot simpler way! Thanks to iOS being a unix system, you become a god with unlimited power and resource! I present elegance.
- (NSString*)lookupHostIPAddressForURL:(NSURL*)url
{
// Ask the unix subsytem to query the DNS
struct hostent *remoteHostEnt = gethostbyname([[url host] UTF8String]);
// Get address info from host entry
struct in_addr *remoteInAddr = (struct in_addr *) remoteHostEnt->h_addr_list[0];
// Convert numeric addr to ASCII string
char *sRemoteInAddr = inet_ntoa(*remoteInAddr);
// hostIP
NSString* hostIP = [NSString stringWithUTF8String:sRemoteInAddr];
return hostIP;
}
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