Versions compatibilty issue ?

[mathJaunot]

Hello,

I run a Node socket io server and some clients that use Python encounter some issues

Server : engine.io: 6.6.1 , socket.io: 4.8.1
Client : python-engineio==4.12.2 python-socketio==5.13.0

Do you know if there's an incompatibility between these versions ?

Behaviours that makes me think that are :

1. The server side event disconnect is not triggered in some heavy load cases
2. There's some issue about engine io on the client side
   2025-08-28 19:09:46 - engineio.client - INFO - Received packet PING data
   2025-08-28 19:09:46 - engineio.client - INFO - Sending packet PONG data
   2025-08-28 19:09:46 - engineio.client - WARNING - WebSocket connection was closed, aborting
   2025-08-28 19:09:46 - engineio.client - INFO - Waiting for write loop task to end
   2025-08-28 19:09:46 - engineio.client - INFO - Exiting write loop task
   Engine.IO connection dropped
   2025-08-28 19:09:46 - socketio.client - INFO - Engine.IO connection dropped
   Connection failed, new attempt in 1.07 seconds
   2025-08-28 19:09:46 - socketio.client - INFO - Connection failed, new attempt in 1.07 seconds
   2025-08-28 19:09:46 - engineio.client - INFO - Exiting read loop task
   Disconnected from Push server. Reason: transport error

Thanks for your answer

Best Regards

[miguelgrinberg]

I'm not aware of any incompatiblities.

The server side event disconnect is not triggered in some heavy load cases

If the server does not trigger a disconnect event then this is an issue in the server. Nothing that the client does can cause this.

There's some issue about engine io on the client side

Have you looked at the server logs to see if there is anything of significance? The logs that you share suggest the connection was dropped, but there is no indication of why.