Get IP address of the current Wi-Fi access point on a iPhone?

Question

I am trying to connect from my iPhone to a socket server running on the same network on my computer. How can I get the local IP address of the computer that is running the socket server?

Answer 1

#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <ifaddrs.h>

- (NSString *)getIPAddress
{
    NSString *address = @"error";
    struct ifaddrs *interfaces = NULL;
    struct ifaddrs *temp_addr = NULL;
    int success = 0;

    // 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:@"en0"])
                {
                    // 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;
}

Answer 2

Your server needs to broadcast itself using the mDNS protocol.

Then on the iPhone, you can simply use gethostbyname to get the IP address. You also have a specific API for that: DNS Service Discovery C Reference.