error 3 Bad request

[rantianhua]

I always received this error message in my wss connection:

 {
    name: 'TRANSPORT_MISMATCH',
    transport: 'websocket',
    previousTransport: 'polling'
}

I want to know what's wrong with my connection and how can I solve it?

[gibloor]

It seems like you're encountering an issue where the frontend is likely using WebSocket, but when Nginx (or whatever you're using) forwards the request to the server, it switches the transport to polling. When the server tries to send a signal using WebSocket, this error occurs.

Configure NGINX!

[darrachequesne]

@gibloor thanks! I have added the list of error code in the troubleshooting guide: https://socket.io/docs/v4/troubleshooting-connection-issues/#troubleshooting-steps