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[英]How to reconnect a returning client (web page) in socket.io to a previously started backend process
[英]How to reconnect to a Web Socket when I refresh the client web page
当刷新客户端网页时,我停止从龙卷风套接字服务器接收数据。 如何重新连接到流?
我尝试将连接对象添加到列表中,然后在关闭时将其从列表中删除,但事实证明,刷新页面时,连接永不关闭,根据服务器保持活动状态,但也不会在客户端再接收数据:(
这是我的龙卷风服务器
# python 3
from tornado import web, httpserver, ioloop, websocket, options
from time import time, sleep
class ChannelHandler(websocket.WebSocketHandler):
"""Handler that handles a websocket channel"""
connections = list()
@classmethod
def urls(cls):
return [(r'/websocket', cls, {})]
def initialize(self):
self.channel = None
def open(self):
# When Client opens a websocket
# add the new connnection to connections
self.connections.append(self)
def on_message(self, message):
# Message received on channel
# keep sending all connected clients the time info
while True:
[client.write_message({'time()': str(time())}) for client in self.connections]
sleep(1)
print('still sending')
def on_close(self):
# Channel is closed
# delete client from active connections if they close connection
self.connections.remove(self)
print('CLOSED connection?')
def check_origin(self, origin):
# Override the origin check if needed
return True
def main():
# Create tornado application and supply URL routes
app = web.Application(ChannelHandler.urls())
# Setup HTTP Server
http_server = httpserver.HTTPServer(app)
http_server.listen(8000, 'localhost')
# Start IO/Event loop
ioloop.IOLoop.instance().start()
if __name__ == '__main__':
main()
套接字客户端是
<script type="text/javascript">
var ws = new WebSocket("ws://localhost:8000/websocket");
ws.onopen = function () {
ws.send("Hello, world");
};
ws.onmessage = function (evt) {
console.log(evt.data);
};
</script>
因此,当刷新cleint网页时,如何继续从套接字服务器接收数据?
while
循环阻塞了整个服务器。 您已经在循环中添加了sleep(1)
调用来暂停循环一秒钟,但是time.sleep
是一个阻塞函数,因此也没有任何帮助。
您需要使用异步替代time.sleep
-Tornado的gen.sleep
。
您还需要将on_message
函数转换为协程。
例:
from tornado import gen
async def on_message(...):
...
while True:
...
await gen.sleep(1)
...
另外 ,请使用set()
而不是list()
来存储连接,以免意外添加重复的连接。
在这种情况下,您还需要稍微修改一下代码。 set
没有append
方法,而是具有add
方法。
connections = set()
...
self.connections.add(self) # to add connection
...
self.connections.remove(self) # to remove connetion
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