Determining own IP address

Question

I've got a socket app that wants to figure out the IP addr of the iPhone it's running on. gethostname followed by gethostbyname works if there's a DNS server but I may be running with static IP addresses in an AdHoc network and in that case gethostbyname fails. What are my other options? I read about NSHost, will that work without DNS server? I also heard about System.Configuration framework but could not find anything related to the IP address of the device.
Thanks,
Andrew

Answer 1

This is actually a fairly tricky thing to determine as you can have multiple IP addresses. Try the following:
// Get my address.
- (NSString *) address
NSMutableString * result = [NSMutableString new];
struct ifaddrs * myaddrs;
if(!getifaddrs(& myaddrs))
for(ifaddrs * ifa = myaddrs; ifa; ifa = ifa->ifa_next)
if(!ifa->ifa_addr)
continue;
if((ifa->ifa_flags & IFF_UP) == 0)
continue;
// buf must be big enough for an IPv6 address
// (e.g. 3ffe:2fa0:1010:ca22:020a:95ff:fe8a:1cf8)
char address[64];
address[0] = 0;
if(strncmp("lo", ifa->ifa_name, 2)
&& ifa->ifaaddr->safamily == AF_INET)
struct sockaddr_in * s4 = (struct sockaddr_in *)(ifa->ifa_addr);
inet_ntop(
ifa->ifaaddr->safamily,
(void *) & (s4->sin_addr),
address,
sizeof(address));
if(strlen(address) > 0)
if([result length] > 0)
[result appendString: @"
[result appendFormat: @"%s:%d", address, [self port]];
freeifaddrs(myaddrs);
return [result autorelease];