socket.io cdn 304 code example
Example 1: socket.io cdn
<script src="https://cdn.socket.io/socket.io-3.0.1.min.js"></script>
Example 2: "https://cdn.socket.io
<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/1.4.5/socket.io.min.js"></script>