iOS Development: Get private IP and port from NSReadStream

I am developing an app for iOS. In my app there is a working TCP-connection to a server, realized via NSStreams. Now I need the port the connection is using which generates some problems.

I can get the IP from iterating through the interfaces of the device but for the portnumber I have to get the information from the socket. In the following code I try to get the socket from my working and open NSInputStream _readstream. The problem is, that CFSocketCopyAddress is nil and I cannot see why. Can somebody else?

Any help is very much appreciated!

// Initializing some variables we need
CFSocketContext context;
memset(&context, 0, sizeof(context));
context.info = (__bridge void*)self;
NSString *property = @"kCFStreamPropertySocketNativeHandle";

// Get hands on the used socket via the socket native handle
CFSocketNativeHandle *socketNativeHandle = (CFSocketNativeHandle*)CFReadStreamCopyProperty((__bridge CFReadStreamRef)(_readStream), (__bridge CFStringRef)(property));
CFSocketRef cfSocket = CFSocketCreateWithNative(NULL, *socketNativeHandle, kCFSocketNoCallBack, nil, &context);

// Ask the socket for the address information
CFDataRef               dataRef = CFSocketCopyAddress(cfSocket);                        // dataRef is always nil :(
struct sockaddr_in      *sockaddr = (struct sockaddr_in*)CFDataGetBytePtr(dataRef);

int portnumber = sockaddr->sin_port;

Solution

OKay, this works for me now. Maybe I can help someone coming from google or from somewhere else....

- (NSNumber*) getPortnumber{
    int             port        = -1;

    CFSocketContext context;
    memset(&context, 0, sizeof(context));
    context.info = (__bridge void*)self;

    // Get Socket native handle from existing stream
    CFDataRef socketData = CFWriteStreamCopyProperty((__bridge CFWriteStreamRef)(_writeStream), kCFStreamPropertySocketNativeHandle);

    // Get the native handle
    CFSocketNativeHandle handle;
    CFDataGetBytes(socketData, CFRangeMake(0, sizeof(CFSocketNativeHandle)), &handle);

    // Get the socket
    CFSocketRef cfSocket = CFSocketCreateWithNative(NULL, handle, kCFSocketNoCallBack, nil, &context);

    // CFSocketCopyAddress will return the address of the socket
    CFDataRef               dataRef = CFSocketCopyAddress(cfSocket);
    struct sockaddr_in      *sockaddr = (struct sockaddr_in*)CFDataGetBytePtr(dataRef);

    // Get the port from the address information
    port = sockaddr->sin_port;

    // Output Objective-C friendly =)
    NSNumber *portnr = [NSNumber numberWithInt:port];
    return portnr;
}