I can't get market depth data from websocket streamming.

I am not getting market depth data from websocket streamming.
I think, In my code, there is no problem.

var access_token="{{$access_token}}"
var ws = new WebSocket(`wss://ws.kite.trade?api_key=${api_key}&access_token=${access_token}`);
var instrument_tokens=JSON.parse(`<?php echo json_encode($instrument_tokens); ?>`);
for(let i=0;i