> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agrihub360.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Live Updates

> Subscribe to a device metric over WebSocket and receive each stored reading as it lands.

Every stored reading is published to a message bus after the `201`. A WebSocket client subscribed to that device and metric receives the row at once. The publish is best-effort: a failure there never fails the post.

## Subscribe

Open a WebSocket to the message bus with one topic.

```
wss://devices.agrihub360.example/messagebus?topic=ahmetricvalue:<device_id>:<metric_id>
```

The first message confirms the subscription:

```
Subscribed to topic: ahmetricvalue:77777777-7777-7777-7777-777777777703:220
```

Each message after that is the topic, a colon, and the stored row as JSON:

```
ahmetricvalue:77777777-7777-7777-7777-777777777703:220:{"device_id":"77777777-7777-7777-7777-777777777703","metric_id":220,"value":"42.5","timestamp":"1784367787126"}
```

## Topics

A topic names one device and one metric. Topics match exactly. There are no wildcards, so a client that wants three metrics from one device opens three subscriptions.

| Topic                                   | Delivers                                        |
| --------------------------------------- | ----------------------------------------------- |
| `ahmetricvalue:<device_id>:<metric_id>` | Every stored reading for that device and metric |

## Reconnecting

A dropped socket delivers nothing for the gap. Readings stored while the client was away are not replayed; read them back through the app. Reconnect with the same topic and delivery resumes from the next reading.