服务如何跑起来

    class URLSpec(object):
        def __init__(self, pattern, handler_class, ···):
            self.regex = re.compile(pattern)
            self.handler_class = handler_class

    class HTTPServer(object):
        def __init__(self, request_callback, ···):
            # request_callback为Application对象
            self.request_callback = request_callback
            self._sockets = {}

        def listen(self, port, address=""):
            self.bind(port, address)
            self.start(1)

        def bind(self, port, address=None, family=socket.AF_UNSPEC):
            # getaddrinfo函数能够处理名字到地址以及服务到端口这两种转换，返回的是一个sockaddr结构的链表而不是一个地址清单
            for res in socket.getaddrinfo(address, port, family, socket.SOCK_STREAM, 0, socket.AI_PASSIVE | socket.AI_ADDRCONFIG):
                sock = socket.socket(af, socktype, proto)
                sock.setblocking(0)
                sock.bind(sockaddr)
                sock.listen(128)
                self._sockets[sock.fileno()] = sock

        def start(self, num_processes=1):
            if not self.io_loop:
                self.io_loop = ioloop.IOLoop.instance()

            for fd in self._sockets.keys():
                self.io_loop.add_handler(fd, self._handle_events, ioloop.IOLoop.READ)

    # IOLoop (fd handler callback timeout)
    class IOLoop(object):
        def __init__(self, impl=None):
            self._impl = impl or _poll()
            self._handlers = {}

        def instance(cls): # current()
            if not hasattr(cls, "_instance"):
                cls._instance = cls()
            return cls._instance

        def add_handler(self, fd, handler, events):
            self._handlers[fd] = stack_context.wrap(handler)
            self._impl.register(fd, events | self.ERROR)


    if hasattr(select, "epoll"):
    # Python 2.6+ on Linux
        _poll = select.epoll
    elif hasattr(select, "kqueue"):
        # Python 2.6+ on BSD or Mac
        _poll = _KQueue
    else:
        try:
            # Linux systems with our C module installed
            import epoll
            _poll = _EPoll
        except:
            # All other systems
            import sys
            if "linux" in sys.platform:
                logging.warning("epoll module not found; using select()")
            _poll = _Select