async _triggerPacketWD () {
    if (!this._packetWDDelay || !this._isOpen) {
      return Promise.resolve()
    }

    debug(
      'packet delay watchdog triggered [last packet %dms ago]',
      Date.now() - this._packetWDLastTS
    )

    this._packetWDTimeout = null
    return this.reconnect()
  }
Trigger the packet watch-dog; called when we haven't seen a new WS packet
for longer than our WD duration (if provided)

@returns {Promise} p
@private