socketio.exceptions.BadNamespaceError: / is not a connected namespace.

[leolo0626]

My code is very similar to the old issue.
miguelgrinberg/Flask-SocketIO#1485
I establish the connection with namespaces before I emit the message.
However, this cause the above error occasionally. And I watched a comment under another old issue.
#634
The repo owner @miguelgrinberg mentions

What I've been telling people as a workaround is to move your emit to the connect event handler, and then it'll work 100%. But for some people this is weird, they prefer to have a sequential logic in their client, so I've seen code that does a sleep(1) between the connect and the emit and that also sort of works.

Could you tell me what is /how to move emit to connect event handler and provide me some examples ? @miguelgrinberg Many thanks

[miguelgrinberg]

This workaround is not necessary anymore. What version of the package are you using?

[leolo0626]

python-socket==5.3.0
python-engineio==4.2.0

[leolo0626]

I initialize three emit event to the same namespace sequentially .
Each function will try to check the connection of socket by using sio.connected. if connection is okay, then it will not re-connect. Otherwise, we will connect to server again. In addition, I observed that when first emit occurs, the server side gives the following error. It makes everything fail afterwards.

What is possible reason for the occurrence of this error.

message async handler error
Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/engineio/asyncio_server.py", line 447, in _trigger_event
ret = await self.handlersevent
File "/usr/local/lib/python3.8/site-packages/socketio/asyncio_server.py", line 565, in _handle_eio_message
await self._handle_connect(eio_sid, pkt.namespace, pkt.data)
File "/usr/local/lib/python3.8/site-packages/socketio/asyncio_server.py", line 441, in _handle_connect
sid = self.manager.connect(eio_sid, namespace)
File "/usr/local/lib/python3.8/site-packages/socketio/base_manager.py", line 54, in connect
self.enter_room(sid, namespace, None, eio_sid=eio_sid)
File "/usr/local/lib/python3.8/site-packages/socketio/base_manager.py", line 121, in enter_room
self.rooms[namespace][room][sid] = eio_sid
File "/usr/local/lib/python3.8/site-packages/bidict/_mut.py", line 78, in setitem
self._put(key, val, self.on_dup)
File "/usr/local/lib/python3.8/site-packages/bidict/_base.py", line 209, in _put
dedup_result = self._dedup_item(key, val, on_dup)
File "/usr/local/lib/python3.8/site-packages/bidict/_base.py", line 258, in _dedup_item
raise ValueDuplicationError(val)
bidict.ValueDuplicationError: xO__Yb4BdGreH-74AAKa

[miguelgrinberg]

I'm sorry I cannot follow what you are describing. Please provide an example client and server with all the code so that I can reproduce the problem(s) that you have here.