title: Send additional data with blob through websockets
body: <p><a href="https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/send" rel="nofollow noreferrer">Websockets</a> support sending of blobs, but how do we send additional text data with them?</p>
  
  <p>My use-case is a file uploader. I am slicing each file in multiple parts, and send max 3 parts at once to the server. On the server, I need a way to identify the order of these slices, so I can reconstruct the file. This is why I need to send the index of the slice along with blob, and the name of the file (multiple files can be uploaded)</p>