---
type: guidelines
---
# Gateway guidelines

## 1. Read-only with respect to acquisition
- The gateway subscribes. It never opens a CAN socket, TX-capable or otherwise.  
- `obd-poller` is the single writer on the bus. Nothing here changes that.

## 2. Aggregate, do not relay
- A 500 kbps CAN bus produces far more traffic than a display can use or a USB
  link should carry. Downsample and summarise here.  
- If the gateway is only forwarding a topic unchanged, that client should have
  subscribed to the broker directly instead.

## 3. To be added