iPhone ==> Get ip address of the current wifi ?

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 (http://www.multicastdns.org/).

Then on the iPhone, you can simply use gethostbyname to get the ip address. You also have specific API for that: http://developer.apple.com/mac/library/documentation/Networking/Reference/DNSServiceDiscovery_CRef/index.html