TL；DR使用^{}同時運行多個協程。Maybe this scenario requires a framework based on events/callbacks rather than one based on coroutines? Tornado?

不，你不需要其他框架。異步應用程序與同步應用程序的整體思想是，在等待結果時，它不會阻塞。不管它是如何實現的，使用協程或回調。I mean, because connection_handler is constantly waiting for incoming messages, the server can only take action after it has received a message from the client, right? What am I missing here?

在同步應用程序中，您將編寫類似msg = websocket.recv()的內容，這將阻塞整個應用程序，直到您收到消息為止(如您所述)。但在異步應用程序中則完全不同。

當你做msg = yield from websocket.recv()時，你會說：暫停connection_handler()的執行，直到websocket.recv()產生某些結果。在coroutine中使用yield from將控制返回到事件循環，以便在等待websocket.recv()的結果時可以執行其他一些代碼。請參閱documentation以更好地了解協同工作的工作原理。Let's say we – additionally – wanted to send a message to the client whenever some event happens. For simplicity, let's send a message periodically every 60 seconds. How would we do that?

在對starting event loop執行阻塞調用之前，可以使用^{}運行任意數量的協程。import asyncio

import websockets

# here we'll store all active connections to use for sending periodic messages

connections = []

@asyncio.coroutine

def connection_handler(connection, path):

connections.append(connection) # add connection to pool

while True:

msg = yield from connection.recv()

if msg is None: # connection lost

connections.remove(connection) # remove connection from pool, when client disconnects

break

else:

print('< {}'.format(msg))

yield from connection.send(msg)

print('> {}'.format(msg))

@asyncio.coroutine

def send_periodically():

while True:

yield from asyncio.sleep(5) # switch to other code and continue execution in 5 seconds

for connection in connections:

print('> Periodic event happened.')

yield from connection.send('Periodic event happened.') # send message to each connected client

start_server = websockets.serve(connection_handler, 'localhost', 8000)

asyncio.get_event_loop().run_until_complete(start_server)

asyncio.async(send_periodically()) # before blocking call we schedule our coroutine for sending periodic messages

asyncio.get_event_loop().run_forever()

下面是一個示例客戶機實現。它要求您輸入名稱，從echo服務器接收它，等待來自服務器的另外兩條消息(這是我們的周期性消息)并關閉連接。import asyncio

import websockets

@asyncio.coroutine

def hello():

connection = yield from websockets.connect('ws://localhost:8000/')

name = input("What's your name? ")

yield from connection.send(name)

print("> {}".format(name))

for _ in range(3):

msg = yield from connection.recv()

print("< {}".format(msg))

yield from connection.close()

asyncio.get_event_loop().run_until_complete(hello())

要點：在Python 3.4.4中，asyncio.async()被重命名為^{}。

調度delayed calls有一些特殊的方法，但它們不適用于協程。

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