我想在 Python 中使用 WebSockets 来让 Web 客户端了解我使用 PySerial 从串行端口读取的数据的最新情况。我目前正在使用以下代码通过单独的线程连续读取串行数据
def read_from_port():
while running:
reading = ser.readline().decode()
handle_data(reading)
thread = threading.Thread(target=read_from_port)
thread.daemon = True
thread.start()
我正在对串行数据执行一些处理,然后如果计算结果与其之前的值不同,则希望向所有连接的 WebSocket 客户端广播一条消息。为此我设置了以下代码
clients = []
def Broadcast(message):
for client in clients:
client.sendMessage(json.dumps(message).encode('utf8'))
print("broadcasted")
worker.broadcast = Broadcast
class WSHandler(tornado.websocket.WebSocketHandler):
def open(self):
print('new connection')
clients.append(self)
def on_message(self, message):
print('message received: %s' % message)
response = handler.HandleRequest(message, self.write_message)
def on_close(self):
print('connection closed')
clients.remove(self)
def check_origin(self, origin):
return True
application = tornado.web.Application([
(r'/ws', WSHandler),
])
if __name__ == "__main__":
http_server = tornado.httpserver.HTTPServer(application)
http_server.listen(8765)
myIP = socket.gethostbyname(socket.gethostname())
print('*** Websocket Server Started at %s***' % myIP)
tornado.ioloop.IOLoop.instance().start()
然后我想在工作人员中使用“广播”方法来广播结果。从工作线程使用此方法会产生以下错误
File "main.py", line 18, in Broadcast
client.write_message(message)
File "/usr/local/lib/python3.8/site-packages/tornado/websocket.py", line 342, in write_message
return self.ws_connection.write_message(message, binary=binary)
File "/usr/local/lib/python3.8/site-packages/tornado/websocket.py", line 1098, in write_message
fut = self._write_frame(True, opcode, message, flags=flags)
File "/usr/local/lib/python3.8/site-packages/tornado/websocket.py", line 1075, in _write_frame
return self.stream.write(frame)
File "/usr/local/lib/python3.8/site-packages/tornado/iostream.py", line 555, in write
future = Future() # type: Future[None]
File "/usr/local/Cellar/[email protected] /cdn-cgi/l/email-protection/3.8.3_1/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/events.py", line 639, in get_event_loop
raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'Thread-1'.
我知道问题是 Tornado write_message 函数不是线程安全的,并且产生此错误是因为我试图直接从工作线程调用该函数。据我所知,在 Tornado 中使用并发代码的推荐方法是通过 asyncio,但我认为线程方法可能更适合这种情况,因为我有一个基本上不断并行运行的循环。
不幸的是,我对 asyncio 以及如何在 Python 中实现线程知之甚少,所以我想找出从不同线程发送 WebSocket 消息的最简单方法是什么。