{
  "id": .....
  "cmd": "SUBSCRIBE",
  "params": ["topic1", "topic2"]
}

{
  "id": "{req_id}",
  "cmd": "SUBSCRIBE",
  "success": true,
  "time": {timestamp},
  "data": ["topic1", "topic2"]
}
Subscribe to one or more topics to start receiving updates. The maximum number of topics to subscribe per request is 20. 
{
  "id": .....
  "cmd": "SUBSCRIBE",
  "params": ["topic1", "topic2"]
}

{
  "id": "{req_id}",
  "cmd": "SUBSCRIBE",
  "success": true,
  "time": {timestamp},
  "data": ["topic1", "topic2"]
}