版本：1.7.3
- https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.3/socket.io.js
- https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.3/socket.io.min.js
- https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.3/socket.io.slim.js
- https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.3/socket.io.slim.min.js