Is upgrading socket.io required while upgrading socket.io-client

[Abhishek325]

Hi folks, I upgraded my socket.io-client (from 2.3.0 to 4.1.1) to address few security issues. My server is still running socket.io 2.3.0 and I don't see anything broken with my app. Is the client supposed to be independent of socket version on server?

[Rc85]

From my experience, yes, it is required. If you have different versions, they will not connect.

[darrachequesne]

I guess it's still working because you are using transports: ["websocket"], in that specific case socket.io@2 is indeed compatible with socket.io-client@4.

That being said, the bump from v2 to v3 was backward incompatible at the protocol level, so a client in v3 (with HTTP long-polling enabled) is not compatible with a server in v2. More information about it here.

You can find the compatibility table here: https://socket.io/docs/v4/client-installation/#Version-compatibility