Does autoupgrade break the EngineIO protocol?

[zackliu]

I find the newly added feature autograde send a upgrade message directly, but from the protocol of Engine.IO https://socket.io/docs/v4/engine-io-protocol/#upgrade clients MUST send a ping packet with the string probe in the payload. I'm not sure whether this implementation break the protocol and may be not work in all the server implementation?

[doghappy]

already implemented, which server are you using?