CFSocket accept callback is not being called. What have I missed?

Question

I'm currently writing a simple TCP server class in Objective-C which should be able to bind to and listen on a particular port. I particular I have a function -(void) start which creates a CFSockets, binds it to the port specified and adds it to a run loop. It looks like this:

- (void) start {
    //This function is called after the initialiser

    if([self isStarted]) //if already started, return without doing anything
        return;


    //create a socket
    CFSocketContext socketCtxt = {0, (__bridge void *)self, NULL, NULL, NULL};
    socket = CFSocketCreate(kCFAllocatorDefault, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketAcceptCallBack, (CFSocketCallBack)&SocketAcceptCallback, &socketCtxt);


    NSAssert(socket, @"Error: Cannot create a socket...");


    int yes = 1;
    setsockopt(CFSocketGetNative(socket), SOL_SOCKET, SO_REUSEADDR, (void *)&yes, sizeof(yes));


//bind it to the desired port
    struct sockaddr_in serverAddress;
    socklen_t nameLen = 0;
    nameLen = sizeof(serverAddress);
    memset(&serverAddress, 0, sizeof(serverAddress));

    serverAddress.sin_len = nameLen;
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_port = htons(self.port);
    serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);

    NSData* address4 = [NSData dataWithBytes:&serverAddress length:nameLen];


    if(kCFSocketSuccess != CFSocketSetAddress(socket, (CFDataRef)address4)) {
        if (socket) CFRelease(socket);
        socket = NULL;
        NSAssert(NO, @"Unable to bind the created socket to the desired port");
    }


    //add to the current run loop
    CFRunLoopSourceRef rls = CFSocketCreateRunLoopSource(kCFAllocatorDefault, socket, 0);


    assert(rls!=0);

    CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopCommonModes);


    //done!

}

I also define the callback function SocketAcceptCallback like this:

static void SocketAcceptCallback(CFSocketRef sock, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) {
    //this method is called after a connection is accepted
    //here we bind the received connection to a pair of
    //NSStreams
    if(type == kCFSocketAcceptCallBack){
        CFSocketNativeHandle nativeSocketHandle = *(CFSocketNativeHandle *)data;

        struct sockaddr_in peerAddress;
        socklen_t peerLen = sizeof(peerAddress);
        NSString * peer = nil;

        if (getpeername(nativeSocketHandle, (struct sockaddr *)&peerAddress, (socklen_t *)&peerLen) == 0) {
            peer = [NSString stringWithUTF8String:inet_ntoa(peerAddress.sin_addr)];
        } else {
            peer = @"Generic Peer";
        }


        NSLog(@"%@ has connected", peer);


        //Find corresponding SocketServer object -- it is passed to the callback in the INFO pointer
        SocketServer *obj = (__bridge SocketServer*)info;

        CFReadStreamRef readStream = NULL;
        CFWriteStreamRef writeStream = NULL;
        CFStreamCreatePairWithSocket(NULL, nativeSocketHandle, &readStream, &writeStream);

         if (readStream && writeStream) {
             CFReadStreamSetProperty(readStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);
             CFWriteStreamSetProperty(writeStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);


             //bridge to NSStreams
             obj.inputStream = (NSInputStream *)readStream;
             obj.outputStream = (NSOutputStream *)writeStream;

             //set delegates
             [obj.inputStream setDelegate:obj];
             [obj.outputStream setDelegate:obj];

             //schedule the runloops
             [obj.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
             [obj.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

             //open connections
             [obj.inputStream open];
             [obj.outputStream open];


         } else {
             // on any failure, need to destroy the CFSocketNativeHandle
             // since we are not going to use it any more
             close(nativeSocketHandle);
         }

        /*
         if (readStream) CFRelease(readStream);
         if (writeStream) CFRelease(writeStream); */
    }
}

In the callback, I bridge the connection to a pair of NSStreams which I have as member fields in my class and which I use to read and write.

Now the problem: I have tried to run this server and connect to it via telnet. It connects, but the aforementioned callback is not being called (I have checked by adding a diagnostic NSLog in it). I suspect I haven't added the socket to a run loop correctly, but I can't find any mistakes myself. Any ideas as to what it might be?