{
  "req": "sub",
  "chs": [
    "book::1"
  ]
}

{
  "req": "unsub",
  "chs": [
    "book::1"
  ]
}

{
  "data": []
}

{
  "data": []
}

{
  "ch": "book::1",
  "ts": 1767225600000,
  "sq": 1234567890,
  "data": {
    "b": [
      [
        "100.00",
        "10.00"
      ]
    ],
    "a": [
      [
        "100.00",
        "10.00"
      ]
    ]
  }
}