Posix reactor base class
| Class | PosixReactorBase | A basis for reactors that use file descriptors. | 
| Class | _SocketWaker | No summary | 
| Class | _FDWaker | The self-pipe trick<http://cr.yp.to/docs/selfpipe.html>, used to wake up the main loop from another thread or a signal handler. | 
| Class | _UnixWaker | This class provides a simple interface to wake up the event loop. | 
| Class | _SIGCHLDWaker | _SIGCHLDWakercan wake up a reactor wheneverSIGCHLDis received. | 
| Class | _DisconnectSelectableMixin | Mixin providing the _disconnectSelectablemethod. | 
| Class | _PollLikeMixin | Mixin for poll-like reactors. | 
| Class | _ContinuousPolling | Schedule reads and writes based on the passage of time, rather than notification. |