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# Publish Subscribe
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Publish Subscribe is also included on the stack. Currently, we have two PubSub implementation available [libp2p-floodsub](https://github.com/libp2p/js-libp2p-floodsub) and [libp2p-gossipsub](https://github.com/ChainSafe/js-libp2p-gossipsub), with many more being researched at [research-pubsub](https://github.com/libp2p/research-pubsub).
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We've seen many interesting use cases appear with this, here are some highlights:
- [Collaborative Text Editing](https://www.youtube.com/watch?v=-kdx8rJd8rQ)
- [IPFS PubSub (using libp2p-floodsub) for IoT](https://www.youtube.com/watch?v=qLpM5pBDGiE).
- [Real Time distributed Applications](https://www.youtube.com/watch?v=vQrbxyDPSXg)
## 1. Setting up a simple PubSub network on top of libp2p
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For this example, we will use MulticastDNS for automatic Peer Discovery. This example is based the previous examples found in [Discovery Mechanisms](../discovery-mechanisms). You can find the complete version at [1.js](./1.js).
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Using PubSub is super simple, you only need to provide the implementation of your choice and you are ready to go. No need for extra configuration.
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First, let's update our libp2p configuration with a pubsub implementation.
```JavaScript
const Libp2p = require('libp2p')
const Gossipsub = require('libp2p-gossipsub')
const node = await Libp2p.create({
addresses: {
listen: ['/ip4/0.0.0.0/tcp/0']
},
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modules: {
transport: [ TCP ],
streamMuxer: [ Mplex ],
connEncryption: [ NOISE ],
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// we add the Pubsub module we want
pubsub: Gossipsub
}
})
```
Once that is done, we only need to create a few libp2p nodes, connect them and everything is ready to start using pubsub.
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```JavaScript
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const topic = 'news'
const node1 = nodes[0]
const node2 = nodes[1]
// Add node's 2 data to the PeerStore
node1.peerStore.addressBook.set(node2.peerId, node2.multiaddrs)
await node1.dial(node2.peerId)
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node1.pubsub.on(topic, (msg) => {
console.log(`node1 received: ${uint8ArrayToString(msg.data)}`)
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})
await node1.pubsub.subscribe(topic)
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// Will not receive own published messages by default
node2.pubsub.on(topic, (msg) => {
console.log(`node2 received: ${uint8ArrayToString(msg.data)}`)
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})
await node2.pubsub.subscribe(topic)
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// node2 publishes "news" every second
setInterval(() => {
node2.pubsub.publish(topic, uint8ArrayFromString('Bird bird bird, bird is the word!'))
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}, 1000)
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```
The output of the program should look like:
```
> node 1.js
connected to QmWpvkKm6qHLhoxpWrTswY6UMNWDyn8hN265Qp9ZYvgS82
node1 received: Bird bird bird, bird is the word!
node1 received: Bird bird bird, bird is the word!
```
You can change the pubsub `emitSelf` option if you want the publishing node to receive its own messages.
```JavaScript
const defaults = {
config: {
pubsub: {
enabled: true,
emitSelf: true
}
}
}
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```
The output of the program should look like:
```
> node 1.js
connected to QmWpvkKm6qHLhoxpWrTswY6UMNWDyn8hN265Qp9ZYvgS82
node1 received: Bird bird bird, bird is the word!
node2 received: Bird bird bird, bird is the word!
node1 received: Bird bird bird, bird is the word!
node2 received: Bird bird bird, bird is the word!
```
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## 2. Future work
libp2p/IPFS PubSub is enabling a whole set of Distributed Real Time applications using CRDT (Conflict-Free Replicated Data Types). It is still going through heavy research (and hacking) and we invite you to join the conversation at [research-CRDT](https://github.com/ipfs/research-CRDT). Here is a list of some of the exciting examples:
- [PubSub Room](https://github.com/ipfs-labs/ipfs-pubsub-room)
- [Live DB - A always in Sync DB using CRDT](https://github.com/ipfs-labs/ipfs-live-db)
- [IIIF Annotations over IPFS, CRDT and libp2p](https://www.youtube.com/watch?v=hmAniA6g9D0&feature=youtu.be&t=10m40s)
- [orbit.chat - p2p chat application, fully running in the browser with js-ipfs, js-libp2p and orbit-db](http://orbit.chat/)