iOS Unable to "Configure one of the app’s sockets for VoIP usage" for background mode

Question

I am trying to set up my app to listen to a tcp-socket even when the app is suspended. I set the voip-background mode in the Info.plist as described in the apple documentation. Now I am stuck where is says: "Configure one of the app’s sockets for VoIP usage.". I am trying to do this with the CFReadStreamSetProperty() methods but the point is how I create the sockets. The creation of the socket is done via the standard C-Library like this:

int mySock = socket(AF_INET, SOCK_STREAM, 0);

This is done inside a .cpp file within an existing library. This is what I have tried to configure the socket for VoIP usage:

CFStreamCreatePairWithSocket(kCFAllocatorDefault, sock, &readStream, &writeStream);
if(readStream && writeStream)
{
   CFReadStreamSetProperty(readStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
   CFWriteStreamSetProperty(writeStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
}

When I step through it it is looking good but unfortunately it does not work. Whenever the app is going from foreground to background/suspended the connection gets lost and any input from the server is ignored. I have no clue if the configuration of the socket can be done like this at all and can not find an answer to it.

Did you register your application with UIBackgroundModes as voip? If not so, iOS won't allow a wakeup due to incomming packets. — Matthias
I am facing the same issue (using a posix socket for voip). Did you manage to get it working ? — Paul Praet

Somu Somu · Accepted Answer · 2013-03-21T06:01:39

This is my first post in this forum. But I found this is working.

Set VOIP in info.plist file
CFReadStreamSetProperty(readStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);

CFWriteStreamSetProperty(writeStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
Use TCP sockets

It didn't work for UDP socket. If I am wrong, please edit this post.

iOS Unable to "Configure one of the app’s sockets for VoIP usage" for background mode

2 Answers