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# Pub/Sub
The Pub/Sub API is implemented by `RedisClient` and `RedisCluster`.
## Pub/Sub with `RedisClient`
Pub/Sub requires a dedicated stand-alone client. You can easily get one by `.duplicate()`ing an existing `RedisClient`:
```typescript
const subscriber = client.duplicate();
subscriber.on('error', err => console.error(err));
await subscriber.connect();
```
When working with a `RedisCluster`, this is handled automatically for you.
### `sharded-channel-moved` event
`RedisClient` emits the `sharded-channel-moved` event when the ["cluster slot"](https://redis.io/docs/reference/cluster-spec/#key-distribution-model) of a subscribed [Sharded Pub/Sub](https://redis.io/docs/manual/pubsub/#sharded-pubsub) channel has been moved to another shard.
The event listener signature is as follows:
```typescript
(
channel: string,
listeners: {
buffers: Set<Listener>;
strings: Set<Listener>;
}
)
```
## Subscribing
```javascript
const listener = (message, channel) => console.log(message, channel);
await client.subscribe('channel', listener);
await client.pSubscribe('channe*', listener);
// Use sSubscribe for sharded Pub/Sub:
await client.sSubscribe('channel', listener);
```
> ⚠️ Subscribing to the same channel more than once will create multiple listeners which will each be called when a message is recieved.
## Publishing
```javascript
await client.publish('channel', 'message');
// Use sPublish for sharded Pub/Sub:
await client.sPublish('channel', 'message');
```
## Unsubscribing
The code below unsubscribes all listeners from all channels.
```javascript
await client.unsubscribe();
await client.pUnsubscribe();
// Use sUnsubscribe for sharded Pub/Sub:
await client.sUnsubscribe();
```
To unsubscribe from specific channels:
```javascript
await client.unsubscribe('channel');
await client.unsubscribe(['1', '2']);
```
To unsubscribe a specific listener:
```javascript
await client.unsubscribe('channel', listener);
```
## Buffers
Publishing and subscribing using `Buffer`s is also supported:
```javascript
await subscriber.subscribe('channel', message => {
console.log(message); // <Buffer 6d 65 73 73 61 67 65>
}, true); // true = subscribe in `Buffer` mode.
await subscriber.publish(Buffer.from('channel'), Buffer.from('message'));
```
> NOTE: Buffers and strings are supported both for the channel name and the message. You can mix and match these as desired.
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