iOS Voip Socket will not run in background

I am getting a VOIP socket to run in the background in an iOS application.

My connection works fine, but it won't wake up when my app goes into the background. If I open the app back up, though, it responds to any messages it got while it was asleep.

I set up my stream like this:

CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault,
                                   (CFStringRef) @"test.iusealocaltestserver.com",
                                   5060,
                                   &myReadStream,
                                   &myWriteStream);
CFReadStreamSetProperty (    myReadStream,
                             kCFStreamNetworkServiceType,
                             kCFStreamNetworkServiceTypeVoIP
                             );

CFSocketNativeHandle native;
CFDataRef nativeProp = CFReadStreamCopyProperty(myReadStream, kCFStreamPropertySocketNativeHandle);

CFDataGetBytes(nativeProp, CFRangeMake(0, CFDataGetLength(nativeProp)), (UInt8 *)&native);
CFRelease(nativeProp);

CFSocketRef theSocket = CFSocketCreateWithNative(kCFAllocatorDefault, native, 0, NULL, NULL);

CFSocketGetContext(theSocket,&theContext);    


CFOptionFlags readStreamEvents = kCFStreamEventHasBytesAvailable | 
kCFStreamEventErrorOccurred     |
kCFStreamEventEndEncountered    |
kCFStreamEventOpenCompleted;

CFReadStreamSetClient(myReadStream,
                           readStreamEvents,
                           (CFReadStreamClientCallBack)&MyCFReadStreamCallback,
                      (CFStreamClientContext *)(&theContext));

CFReadStreamScheduleWithRunLoop(myReadStream, CFRunLoopGetCurrent(),
                                kCFRunLoopCommonModes);

Then my callback is set up like this:

static void MyCFReadStreamCallback(CFReadStreamRef stream, CFStreamEventType type, void *pInfo);

static void MyCFReadStreamCallback (CFReadStreamRef stream, CFStreamEventType type, void *pInfo)
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSLog(@"Callback Happened");

   [pool release];
}

"Callback Happened" is getting called when I receive data and the app is open, but it doesn't if the app is minimized. When the app comes back up, though, it processes any data it received while minimized.

I added the voip tag to the info.plist. My CFReadStreamSetProperty returns true. I am running on a device not a simulator. It still doesn't work though, so I dont know what my problem could be. I probably just did something silly, but there's almost nothing online to check my code against.

EDIT: I can't test any of the answers because I am no longer working on this project and don't have access to a mac/iOs sdk. If someone with a similar problem found one of the below answers useful, let me know and I will vote it best answer.

If you want to let your VOIP application run in background , except those base settings in plist file, you need a TCP socket who's property is set to VOIP, than the iOS system will take care this socket for you, when your application enter background , every thing was 'sleep' except that tcp socket. and if VOIP server send some data thought that TCP socket, your application will be awake up for 10 secs. during this time, you can post a local notification.

Only Tcp socket can be set as VOIP Socket. But from i know , mostly VOIP application are based on UDP socket. if you do not want to separate the control socket from the data socket. you should create another tcp socket which is focus on 'awake' your application , and from my personal experience , it's very hard to keep this 'awake' signal and the real sip control signal synchronize, the application always miss the sip invite request.

So,the best way is separating the sip control single from the UDP data socket , make it as a tcp socket , this is the best solution , but never use tcp socket to transfer voice data.

Another dirty way: keep the application awake all the time. As i said , each TCP single the application received thought that 'VOIP' tcp socket , will keep application awake for 10 seconds, so at the end of this duration(after 9 secs) , you can send a response to the server to ask for another signal , when the next signal arrived, the application will be awake again,after 9 secs , send response again. keep doing this, your application will awake forever.