Strange issue with VoIP socket(stream) only on one iPhone

Question

I have recently encountered very strange issue.

I have a VoIP app. I install the same build on 4 iPhones (3 iPhone 5s and 1 iPhone4(iOS6.1)). Then I put app into background. 2 iPhones 5s and iPhone4 keep receiving data as they supposed and only one particular device(iPhone 5s) stops receiving network data. All phones are in the same WiFi network and connect to the same service. 2 of them have sim cards 2 of them don't. The problematic one has sim card.

I have my app set up as VoIP app with NSStreamNetworkServiceTypeVoIP set to NSInputStream

NSInputStream *_inputStream ;
CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)host, port, &readStream, &writeStream);

_outputStream = CFBridgingRelease(writeStream);
_inputStream = CFBridgingRelease(readStream);
[_inputStream setProperty:NSStreamNetworkServiceTypeVoIP forKey:NSStreamNetworkServiceType];

I would appreciate any hints why this can happen.

Answer 1

OK, so after hours of debugging I started trying to reboot device and reset settings.

Device reboot was useless.

After I have reset network settings problem has disappeared.

Answer 2

I have the same issue and the only fix I found was to restart the network settings.