Question

I just like to ask if it is possible to identify the IP Address of a device (e.g. a printer) using its Hostname even if its Bonjour setting is turned off? Also can you give me an example on how to do it? I am developing an app in iOS that should handle this scenario.

I have looked at the following:

1. getaddrinfo
2. CFHostStartInfoResolution

but they work only if the device’s bonjour is turned ON.

Answer 1

Assuming the hostname (let’s say nameOfTheDevice) is registered with the zone’s authoritative DNS server, you can use CFHost to look up an address or hostname. For example:

NSString* hostname = @"nameOfTheDevice";
CFHostRef hostRef = CFHostCreateWithName(kCFAllocatorDefault, (CFStringRef)hostname);

Boolean lookup = CFHostStartInfoResolution(hostRef, kCFHostAddresses, NULL);
NSArray* addresses = (NSArray*)CFHostGetAddressing(hostRef, &lookup);

[addresses enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    NSString *strDNS = [NSString stringWithUTF8String:inet_ntoa(*((struct in_addr *)obj))];
       NSLog(@"Resolved %d->%@", idx, strDNS);
  }];

(Remember to put error checks in your production code). Bear in mind that if the DNS server isn’t aware of that hostname, there’s nothing you can do. It’s not safe to assume that you’ll be able to perform a successful lookup, especially on a home network where built-in DHCP/DNS servers have widely varying capabilities.