版本：2.3.0
- https://cdn.bootcdn.net/ajax/libs/socket.io/2.3.0/socket.io.dev.js
- https://cdn.bootcdn.net/ajax/libs/socket.io/2.3.0/socket.io.js
- https://cdn.bootcdn.net/ajax/libs/socket.io/2.3.0/socket.io.slim.dev.js
- https://cdn.bootcdn.net/ajax/libs/socket.io/2.3.0/socket.io.slim.js