Example of how to get iOS device IP address. Modified version of function at http://zachwaugh.me/posts/programmatically-retrieving-ip-address-of-iphone/ (also works on OS X)

gistfile1.txt

#include "TargetConditionals.h"
#include <ifaddrs.h>
#include <arpa/inet.h>

+ (NSString *)deviceIPAddress
{
    NSString *address = @"error";
    struct ifaddrs *interfaces = NULL;
    struct ifaddrs *temp_addr = NULL;
    int success = 0;
    
    #if TARGET_IPHONE_SIMULATOR
        #error Specify network interface for computer(iPhone simulator) below and then remove this line
        NSString *networkInterface = @"en1";
    #else
        NSString *networkInterface = @"en0";
    #endif
    
    // retrieve the current interfaces - returns 0 on success
    success = getifaddrs(&interfaces);
    if (success == 0) {
        // Loop through linked list of interfaces
        temp_addr = interfaces;
        while (temp_addr != NULL) {
            if( temp_addr->ifa_addr->sa_family == AF_INET) {
                // Check if interface is en0 which is the wifi connection on the iPhone
                if ([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:networkInterface]) {
                    // Get NSString from C String
                    address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
                }
            }
            
            temp_addr = temp_addr->ifa_next;
        }
    }
    
    // Free memory
    freeifaddrs(interfaces);
    
    return address;
}