Hyperswarm
Hyperswarm helps to find and connect to peers announcing a common 'topic' that can be anything. Using Hyperswarm, 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.
Notable features include:
An improved UDP holepunching algorithm that uses arbitrary DHT nodes (optionally selected by the connecting peers) to proxy necessary metadata while being maximally privacy-preserving.
A custom-built transport protocol, UDX, that takes advantage of the holepunching algorithm to avoid unnecessary overhead (it doesn't include handshaking since holepunching takes care of that, for example). It's blazing fast.
A simplified DHT API that closely resembles NodeJS's
net
module, but using public keys instead of IP addresses.
Basic:
Methods:
Events:
Installation
Install with npm:
API
const swarm = new Hyperswarm([options])
const swarm = new Hyperswarm([options])
Constructs a new Hyperswarm instance.
The following table describes the properties of the optional options
object.
Properties:
swarm.connecting
swarm.connecting
A number that indicates connections in progress.
swarm.connections
swarm.connections
A set of all active client/server connections.
swarm.peers
swarm.peers
A Map containing all connected peers, of the form: (Noise public key hex string) -> PeerInfo object
See the PeerInfo
API for more details.
swarm.dht
swarm.dht
A HyperDHT
instance. Useful for lower-level control over Hyperswarm's networking.
Methods
const discovery = swarm.join(topic, [options])
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:
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 atopic
for the first one.
Events
swarm.on('connection', (socket, peerInfo) => {})
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', () => {})
swarm.on('update', () => {})
Emitted when internal values are changed, useful for user interfaces.
For instance, the 'update' event is emitted when
swarm.connecting
orswarm.connections
changes.
Clients and Servers
In Hyperswarm, there are two ways for peers to join the swarm: client mode and server mode. Previously in Hyperswarm v2, these were called 'lookup' and 'announce', but we now think 'client' and 'server' are more descriptive.
When user joins 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 this user keypair to the DHT so that other peers can discover the user server. When server connections are emitted, they are not associated with a specific topic -- the server only knows it received an incoming connection.
When user joins 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).
Methods
await swarm.leave(topic)
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.
swarm.joinPeer(noisePublicKey)
swarm.joinPeer(noisePublicKey)
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.
swarm.leavePeer(noisePublicKey)
swarm.leavePeer(noisePublicKey)
Stops 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)
const discovery = swarm.status(topic)
Gets the PeerDiscovery
object associated with the topic, if it exists.
await swarm.listen()
await swarm.listen()
Explicitly starts listening for incoming connections. This will be called internally after the first join
, so it rarely needs to be called manually.
await swarm.flush()
await swarm.flush()
Waits 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 byswarm.on('connection')
immediately after they're opened.
PeerInfo
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.
Properties:
peerInfo.publicKey
peerInfo.publicKey
The peer's Noise public key.
peerInfo.topics
peerInfo.topics
An Array of topics that this Peer is associated with -- topics
will only be updated when the Peer is in client mode.
peerInfo.prioritized
peerInfo.prioritized
If true, the swarm will rapidly attempt to reconnect to this peer.
Methods:
peerInfo.ban(banStatus = false)
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 for both controlling discovery behavior and responding to lifecycle changes during discovery.
Methods
await discovery.flushed()
await discovery.flushed()
Waits 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 })
await discovery.refresh({ client, server })
Updates 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()
await discovery.destroy()
Stops 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.
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