| Parameters | cfSocket | The CFSocket which has got some activity. | 
 | callbackType | The type of activity that we are being notified of.  Either kCFSocketReadCallBack or kCFSocketWriteCallBack. | 
 | ignoredAddress | Unused, because this is not used for either of the callback types we register for. | 
 | ignoredData | Unused, because this is not used for either of the callback types we register for. | 
 | context | The data associated with this callback by CFSocketCreateWithNative (in CFReactor._watchFD).  A 2-tuple of (int, CFRunLoopSource). |