socket.io

• https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.4/socket.io.
• https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.4/socket.io.min.
• https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.4/socket.io.slim.
• https://cdn.bootcdn.net/ajax/libs/socket.io/1.7.4/socket.io.slim.min.