// server: running at localhost:3001
const io = new Server(server, {
  cors: {
    origin: 'http://localhost:3001'
  }
})

// client: running at localhost:3000
import { io } from 'socket.io-client'
const socket = io('/ws')

// vite.config.ts
export default defineConfig({
 // ...
  server: {
    proxy: {
      '/ws': {
        target: 'http://localhost:3001',
        ws: true,
        rewrite: (path) => path.replace(/^\/ws/, ''),
        changeOrigin: true
      }
    }
  }
})

import { io } from 'socket.io-client'
const socket = io('localhost:3001')