p2pswarm

A high-level API for finding and connecting to peers who are interested in a "topic."

Installation

npm install p2pswarm

Usage

const P2Pswarm = require('p2pswarm')

const swarm1 = new P2Pswarm()
const swarm2 = new P2Pswarm()

swarm1.on('connection', (conn, info) => {
  // swarm1 will receive server connections
  conn.write('this is a server connection')
  conn.end()
})

swarm2.on('connection', (conn, info) => {
  conn.on('data', data => console.log('client got message:', data.toString()))
})

const topic = Buffer.alloc(32).fill('hello world') // A topic must be 32 bytes
const discovery = swarm1.join(topic, { server: true, client: false })
await discovery.flushed() // Waits for the topic to be fully announced on the DHT

swarm2.join(topic, { server: false, client: true })
await swarm2.flush() // Waits for the swarm to connect to pending peers.

// After this point, both client and server should have connections

P2Pswarm API

const swarm = new P2Pswarm(opts = {})

Construct a new P2Pswarm instance.

opts can include:

• keyPair: A Noise keypair that will be used to listen/connect on the DHT. Defaults to a new key pair.
• seed: A unique, 32-byte, random seed that can be used to deterministically generate the key pair.
• maxPeers: The maximum number of peer connections to allow.
• firewall: A sync function of the form remotePublicKey => (true|false). If true, the connection will be rejected. Defaults to allowing all connections.
• dht: A DHT instance. Defaults to a new instance.

swarm.connecting

Number that indicates connections in progress.

swarm.connections

A set of all active client/server connections.

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

A @p2pswarm/dht instance. Useful if you want lower-level control over P2Pswarm's networking.

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 example: emitted when swarm.connecting or swarm.connections changes.

const discovery = swarm.join(topic, opts = {})

Start discovering and connecting to peers sharing a common topic. As new peers are connected to, they will be emitted from the swarm as connection events.

topic must be a 32-byte Buffer opts can include:

• server: Accept server connections for this topic by announcing yourself to the DHT. Defaults to true.
• client: Actively search for and connect to discovered servers. Defaults to true.

Returns a PeerDiscovery object.

Clients and Servers

In P2Pswarm, there are two ways for peers to join the swarm: client mode and server mode. If you've previously used P2Pswarm 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.

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)

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 announces, 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.

PeerDiscovery API

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.

PeerInfo API

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.

peerInfo.publicKey

The peer's Noise public key.

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

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

peerInfo.ban()

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

License

MIT