Question

I’m trying to connect to a server in a custom GCD queue. This is how I’m doing it.

- (void) initNetworkCommunication{
    if(!self.connQueue){
        self.connQueue = dispatch_queue_create("connection_queue", NULL);
    }

    dispatch_async(self.connQueue, ^(void) {
        if(self.inputStream ==nil && self.outputStream ==nil) {
            CFReadStreamRef readStream;
            CFWriteStreamRef writeStream;
            NSString *host= [[NSUserDefaults standardUserDefaults] objectForKey:@"ip_preference"];
            NSNumber *portNum = [[NSUserDefaults standardUserDefaults] objectForKey:@"port_preference"];

            int port = [portNum intValue];
            CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)host, port, &readStream, &writeStream);

            CFReadStreamSetProperty(readStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
            CFWriteStreamSetProperty(writeStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);  

            self.inputStream = (__bridge NSInputStream *)readStream;
            self.outputStream = (__bridge NSOutputStream *)writeStream;
            [self.inputStream setDelegate:self];
            [self.outputStream setDelegate:self];

            [self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
            [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];

            [self.outputStream open];
            [self.inputStream open];
        } else {
            NSLog(@"persistant connection alerady opened");
            return;
        }
    });
}

Now, if I write this piece of code in dispatch_sync, it calls delegate function correctly.

- (void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent

But, when I use dispatch_asynch, which is what I want to do, it does not call my delegate function.

From what I’ve read on SO so far, GCD queues have a runloop associated with them but these are not run by the system and we need to do so ourselves. I understand this in theory, but but how is it done. Dispatch sources associated with this somehow?

Thank You in advance.

Answer 1

Add this method after [self.inputStream open];

[[NSRunLoop currentRunLoop]run];

This puts the receiver into a permanent loop, during which time it processes data from all attached input sources.
See apple docs about RunLoops