Vue 3 Composition API + socket.io

Migrating from Vue 2 to Vue 3, you might want to start using Composition API.

If you want to use socket.io you can search 'vue 3 socket.io' and find vue-3-socket.io. You will see following in it's readme:

this.sockets.subscribe('EVENT_NAME', (data) => {
    this.msg = data.message;
});

But Vue 3 Composition API is about to use setup() or <script setup> and there's no this.

So you have to use socket.io directly, without Vue plugin:

socket.io.js

export const useSocketIO = () => {
    const socket = io('ws://localhost:3000')
    return {
        socket,
    }
}

MyComponent.vue

<script>
import { defineComponent } from 'vue'
export default defineComponent({
    setup() {
        const { socket } = useSocketIO()
        socket.on('welcome', () => { console.log('welcome') })
    }
})
</script>

But why not just export socket from socket.io.js and import it in a component? If I do that, I can emit events but cannot subscribe on them. Maybe it's because I use Quasar 2 with SSR mode.