Uncaught TypeError: Cannot read property 'sid' of undefined socket.io.client

Question

I am using socket.io.client in a spfx react app and getting this error while doing the socket connection:

Uncaught TypeError: Cannot read property 'sid' of undefined

Answer 1

Make sure you have same version of socket.io in both server side and client side. Because socket.io 2.0 is no longer compatible with 3.0. you can check it in their api docs https://socket.io/docs/v3/migrating-from-2-x-to-3-0/index.html

Answer 2

"socket.io-client": "^3.0.1" has this issue. it is the latest released version.

On downgrading the version to "socket.io-client": "^2.3.1" the issue got resolved.