iOS: App is hanging when trying to close the stream

Question

I created NSStreams to transfer something using the below code:

dispatch_async(dispatch_get_main_queue(), ^{
    // open input
    [self.inputStream  setDelegate:controller];
    [self.inputStream  scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.inputStream  open];

    // open output
    [self.outputStream setDelegate:controller];
    [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outputStream open];
});

At some point, I want to close the streams using the below code:

    // Shut down input
    [self.inputStream close];
    self.inputStream = nil;

    // Shut down output
    [self.outputStream close];
    self.outputStream = nil;

    NSLog(@"input streams status:%i", [self.inputStream streamStatus]);
    NSLog(@"output streams status:%i", [self.outputStream streamStatus]);
    NSLog(@"input streams status:%@", [self.inputStream streamError]);
    NSLog(@"output streams status:%@", [self.outputStream streamError]);

All input/output streams are strong properties.

Stream status return zero, but my app hangs. When I put device in debug mode, the monitor shows that my device CPU start running in 98+% after close method called. It seems like it's waiting for something to finish, but I still don't know what that is.

Does anyone know what may cause this issues?

If you pause the app in debug mode, can you see what's active on your threads? — Phillip Mills, Oct 24 '16 at 19:59
Your NSLogs at the end there won't work properly because you set the streams to nil in the lines above. Try logging between closing the stream, and setting it to nil. — Mark, Oct 24 '16 at 22:46

score 0 · Accepted Answer · answered Oct 24 '16 at 22:44

Try removing the streams from the run loop.

// Shut down input
[self.inputStream close];
[self.inputStream removeFromRunLoop: [NSRunLoop currentRunLoop] forMode: NSDefaultRunLoopMode];
self.inputStream = nil;

// Shut down output
[self.outputStream close];
[self.outputStream removeFromRunLoop: [NSRunLoop currentRunLoop] forMode: NSDefaultRunLoopMode];
self.outputStream = nil;

More information can be found here.

iOS: App is hanging when trying to close the stream

1 Answers1