You might no longer have this issue, but if there's another application on your machine attempting to connect to a socket.io server on the same port used by Express, it could cause a conflict.

In many cases, this is due to the In-Game Overlay of NVidia GeForce Experience. You can refer to this explanation to identify the source of the issue: Superuser Link.

The most efficient solution is to restart your device, which will allow applications to reset their connections and free up the port.