title: flask socketio emit to specific user
body: <p>I see there is a question about this topic, but the specific code is not outlined. Say I want to emit only to the first client.</p>
  
  <p>For example (in events.py):</p>
  
  <pre><code>clients = []
  
  @socketio.on('joined', namespace='/chat')
  def joined(message):
      """Sent by clients when they enter a room.
      A status message is broadcast to all people in the room."""
      #Add client to client list
      clients.append([session.get('name'), request.namespace])
      room = session.get('room')
      join_room(room)
      emit('status', {'msg': session.get('name') + ' has entered the room.'}, room=room)
      #I want to do something like this, emit message to the first client
      clients[0].emit('status', {'msg': session.get('name') + ' has entered the room.'}, room=room)
  </code></pre>
  
  <p>How is this done properly?</p>
  
  <p>Thanks</p>