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Hyperswarm allows you to find and connect to peers announcing a common 'topic' that can be anything. With Hyperswarm, you can discover and connect peers with a shared interest over a distributed network. For example, we often use Hypercore's discovery key as the swarm topic for discovering peers to replicate with.
Hyperswarm offers a simple interface to abstract away the complexities of underlying modules such as HyperDHT and SecretStream. These modules can also be used independently for specialized tasks.


Install with npm:
npm install hyperswarm


const swarm = new Hyperswarm([options])

Construct a new Hyperswarm instance.
The following table describes the properties of the optional options object.
A Noise keypair will be used to listen/connect on the DHT. Defaults to a new key pair.
A unique, 32-byte, random seed that can be used to deterministically generate the key pair.
The maximum number of peer connections allowed.
A sync function of the form remotePublicKey => (true|false). If true, the connection will be rejected. Defaults to allowing all connections.
A DHT instance. Defaults to a new instance.



A number that indicates connections in progress.


A set of all active client/server connections.


A Map containing all connected peers, of the form: (Noise public key hex string) -> PeerInfo object
See the PeerInfo API for more details.


A HyperDHT instance. Useful if you want lower-level control over Hyperswarm's networking.


const discovery = swarm.join(topic, [options])

Returns a PeerDiscovery object.
Start discovering and connecting to peers sharing a common topic. As new peers are connected, they will be emitted from the swarm as connection events.
topic must be a 32-byte Buffer and use a publicly sharable id, typically a Hypercore discoveryKey which we can then link to (join will leak the topic to DHT nodes).
options can include:
Accept server connections for this topic by announcing yourself to the DHT
Actively search for and connect to discovered servers
Calling swarm.join() makes this core directly discoverable. To ensure that this core remains discoverable, Hyperswarm handles the periodic refresh of the join. For maximum efficiency, fewer joins should be called; if sharing a single Hypercore that links to other Hypercores, only join a topic for the first one.


swarm.on('connection', (socket, peerInfo) => {})

Emitted whenever the swarm connects to a new peer.
socket is an end-to-end (Noise) encrypted Duplex stream.
peerInfo is a PeerInfo instance.

swarm.on('update', () => {})

Emitted when internal values are changed, useful for user interfaces.
For instance, the 'update' event is emitted when swarm.connecting or swarm.connections changes.

Clients and Servers

In Hyperswarm, there are two ways for peers to join the swarm: client mode and server mode. If you've previously used Hyperswarm v2, these were called 'lookup' and 'announce', but we now think 'client' and 'server' are more descriptive.
When you join a topic as a server, the swarm will start accepting incoming connections from clients (peers that have joined the same topic in client mode). Server mode will announce your keypair to the DHT so that other peers can discover your server. When server connections are emitted, they are not associated with a specific topic -- the server only knows it received an incoming connection.
When you join a topic as a client, the swarm will do a query to discover available servers, and will eagerly connect to them. As with server mode, these connections will be emitted as connection events, but in client mode, they will be associated with the topic (info.topics will be set in the connection event).


await swarm.leave(topic)

Stop discovering peers for the given topic.
topic must be a 32-byte Buffer
If a topic was previously joined in server mode, leave will stop announcing the topic on the DHT.
If a topic was previously joined in client mode, leave will stop searching for servers announcing the topic.
leave will not close any existing connections.


Establish a direct connection to a known peer.
noisePublicKey must be a 32-byte Buffer
As with the standard join method, joinPeer will ensure that peer connections are reestablished in the event of failures.


Stop attempting direct connections to a known peer.
noisePublicKey must be a 32-byte Buffer
If a direct connection is already established, that connection will not be destroyed by leavePeer.

const discovery = swarm.status(topic)

Get the PeerDiscovery object associated with the topic, if it exists.

await swarm.listen()

Explicitly start listening for incoming connections. This will be called internally after the first join, so it rarely needs to be called manually.

await swarm.flush()

Wait for any pending DHT announcements, and for the swarm to connect to any pending peers (peers that have been discovered, but are still in the queue awaiting processing).
Once a flush() has completed, the swarm will have connected to every peer it can discover from the current set of topics it's managing.
flush() is not topic-specific, so it will wait for every pending DHT operation and connection to be processed -- it's quite heavyweight, so it could take a while. In most cases, it's not necessary, as connections are emitted by swarm.on('connection') immediately after they're opened.


swarm.on('connection', ...) emits a PeerInfo instance whenever a new connection is established.
There is a one-to-one relationship between connections and PeerInfo objects -- if a single peer announces multiple topics, those topics will be multiplexed over a single connection.



The peer's Noise public key.


An Array of topics that this Peer is associated with -- topics will only be updated when the Peer is in client mode.


If true, the swarm will rapidly attempt to reconnect to this peer.


peerInfo.ban(banStatus = false)

Ban or unban the peer. Banning will prevent any future reconnection attempts, but it will not close any existing connections.

Peer Discovery

swarm.join returns a PeerDiscovery instance which allows you to both control discovery behavior, and respond to lifecycle changes during discovery.


await discovery.flushed()

Wait until the topic has been fully announced to the DHT. This method is only relevant in server mode. When flushed() has completed, the server will be available to the network.

await discovery.refresh({ client, server })

Update the PeerDiscovery configuration, optionally toggling client and server modes. This will also trigger an immediate re-announce of the topic when the PeerDiscovery is in server mode.

await discovery.destroy()

Stop discovering peers for the given topic.
If a topic was previously joined in server mode, leave will stop announcing the topic on the DHT.
If a topic was previously joined in client mode, leave will stop searching for servers announcing the topic.