title: How can I use Websocket transport and async_mode=threading in flask-socketio at the same time?
body: <p>I'm setting up a socket.io server, and we have several background threads that call long, blocking methods which poll data. We also want to emit data to the socket.io client from these threads. We were running into issues where these threads would emit something and it would take forever for it to be pushed to clients, until we switched to async_mode='threading'. Then everything worked perfectly, except we now get the warning:</p>
  
  <p>WebSocket transport not available. Install eventlet or gevent and gevent-websocket for improved performance.</p>
  
  <p>These modules are installed, but not being used when using threading mode. How can we have both background threads that always run and don't call socketio.sleep, while at the same time using Websocket transport instead of threading? Thanks</p>