Session ID unknown
socket.io
#TIL 37 - How to fix Session ID unknown with socket.io
If you're using Socket.io in your web application, you may encounter an issue where the Session ID is unknown. The solution is disabling HTTP long-polling and using only WebSockets for communication between the client and server.
// client-side
const socket = io({
transports: ["websocket"] // HTTP long-polling is disabled
});
The root cause is enabling "sticky session" if HTTP long-polling is enabled (which is the default). You can read more about why sticky sessions are required and how to implement them in the Socket.io documentation: https://socket.io/docs/v4/using-multiple-nodes/#why-is-sticky-session-required
