Determining IP Address from URL in iOS

Question

I need to get the IP address of a CDN from it\'s URL in an iOS app. From a long stack search, i\'ve determined a method for doing this with the following:

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Answer 1

Here is a Swift 3.1 version of converting a URL hostname to IP address.

import Foundation
private func urlToIP(_ url:URL) -> String? {
  guard let hostname = url.host else {
    return nil
  }

  guard let host = hostname.withCString({gethostbyname($0)}) else {
    return nil
  }

  guard host.pointee.h_length > 0 else {
    return nil
  }

  var addr = in_addr()
  memcpy(&addr.s_addr, host.pointee.h_addr_list[0], Int(host.pointee.h_length))

  guard let remoteIPAsC = inet_ntoa(addr) else {
    return nil
  }

  return String.init(cString: remoteIPAsC)
}

Answer 2

Maybe this function will work?

#import <netdb.h>
#include <arpa/inet.h>

- (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;
}

Answer 3

I had no problems compiling that code with the following includes:

#import <netdb.h>
#include <arpa/inet.h>