## MedplumClient.getMasterSubscriptionEmitter() method

Get the master `SubscriptionEmitter` for the `SubscriptionManager`.

The master `SubscriptionEmitter` gets messages for all subscribed `criteria` as well as WebSocket errors, `connect` and `disconnect` events, and the `close` event.
It can also be used to listen for `heartbeat` messages.

----

**Signature:**

```typescript
getMasterSubscriptionEmitter(): SubscriptionEmitter;
```

**Returns:**

[SubscriptionEmitter](/content/docs/sdk/core.subscriptionemitter) the master `SubscriptionEmitter` from the `SubscriptionManager`.

## Example

### Listening for `heartbeat`:

```ts
const masterEmitter = medplum.getMasterSubscriptionEmitter();

masterEmitter.addEventListener('heartbeat', (bundle: Bundle<SubscriptionStatus>) => {

console.log(bundle?.entry?.[0]?.resource); // A `SubscriptionStatus` of type `heartbeat`
});
```