dSwarm

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

npm install dswarm

Usage

const dswarm = require('dswarm')
const crypto = require('crypto')

const swarm = dswarm()

// look for peers listed under this topic
const topic = crypto.createHash('sha256')
  .update('my-dswarm-topic')
  .digest()

swarm.join(topic, {
  lookup: true, // find & connect to peers
  announce: true // optional- announce self as a connection target
})

swarm.on('connection', (socket, info) => {
  console.log('new connection!', info)

  // you can now use the socket as a stream, eg:
  // process.stdin.pipe(socket).pipe(process.stdout)
})

API

swarm = dswarm([options])

Create a new network instance

Options include:

{
  // Optionally overwrite the default set of bootstrap servers
  bootstrap: [addresses],
  // Set to false if this is a long running instance on a server
  // When running in ephemeral mode you don't join the DHT but just 
  // query it instead. If unset, or set to a non-boolean (default undefined)
  // then the node will start in short-lived (ephemeral) mode and switch 
  // to long-lived (non-ephemeral) mode after a certain period of uptime
  ephemeral: undefined,
  // total amount of peers that this peer will connect to
  maxPeers: 24,
  // set to a number to restrict the amount of server socket
  // based peer connections, unrestricted by default.
  // setting to 0 is the same as Infinity, to disallowe server
  // connections set to -1
  maxServerSockets: Infinity,
  // set to a number to restrict the amount of client sockets
  // based peer connections, unrestricted by default.
  maxClientSockets: Infinity,
  // apply a filter before connecting to the peer
  validatePeer: (peer) => true,
  // configure peer management behaviour
  queue: {
    // an array of backoff times, in millieconds
    // every time a failing peer connection is retried
    // it will wait for specified milliseconds based on the
    // retry count, until it reaches the end of the requeue
    // array at which time the peer is considered unresponsive
    // and retry attempts cease
    requeue: [ 1000, 5000, 15000 ],
    // configure when to forget certain peer characteristics
    // and treat them as fresh peer connections again
    forget: {
      // how long to wait before forgetting that a peer
      // has become unresponsive
      unresponsive: 7500,
      // how long to wait before fogetting that a peer
      // has been banned
      banned: Infinity
    },
    // attempt to reuse existing connections between peers across multiple topics
    multiplex: false
  }
}

swarm.join(topic[, options, onjoin])

Join the swarm for the given topic. This will cause peers to be discovered for the topic ('peer' event). Connections will automatically be created to those peers ('connection' event).

The announce and lookup parameters should be set according to your process' expected behavior and lifetime. If your process is:

• Joining the topic temporarily, set lookup: true and announce: false.
• Joining the topic for a long time, set both lookup: true and announce: true.
• Joining the topic and likely to receive a lot of connections (e.g. it runs persistently in the cloud) then set lookup: false and announce: true.

Parameters:

• topic. Buffer. The identifier of the peer-group to list under. Must be 32 bytes in length.
• options. Object.
  • announce. Boolean. List this peer under the the topic as a connectable target? Defaults to false.
  • lookup. Boolean. Look for peers in the topic and attempt to connect to them? If announce is false, this automatically becomes true.
• onjoin. A function that is called when your topic has been fully announced to the local network and the DHT.

swarm.leave(topic[, onleave])

Leave the swarm for the given topic.

• topic. Buffer. The identifier of the peer-group to delist from. Must be 32 bytes in length.
• onleave. A function that is called when your topic has been fully unannounced to the local network and the DHT.

obj = swarm.status(topic)

Returns an object indicating wheather a topic is being announced or performing a lookup, or null if the topic is unknown

swarm.connect(peer, (err, socket, info) => {})

Establish a connection to the given peer. You usually won't need to use this function, because dswarm connects to found peers automatically.

• peer. The object emitted by the 'peer' event.
• cb. Function.
  • err. Error.
  • socket. The established TCP or UTP socket.
  • info. Object describing the connection.
    • type. String. Should be either 'tcp' or 'utp'.
    • client. Boolean. If true, the connection was initiated by this node.
    • peer. Object describing the peer. (Will be the same object that was passed into this method.)

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

A new connection has been created. You should handle this event by using the socket.

• socket. The established TCP or UTP socket.
• info. Object describing the connection.
  • type. String. Should be either 'tcp' or 'utp'.
  • client. Boolean. If true, the connection was initiated by this node.
  • topics. Array. The list of topics associated with this connection (when multiplex: true)
  • peer. Object describing the peer. Will be null if client === false.
    • port. Number.
    • host. String. The IP address of the peer.
    • local. Boolean. Is the peer on the LAN?
    • referrer. Object. The address of the node that informed us of the peer.
      • port. Number.
      • host. String. The IP address of the referrer.
      • id. Buffer.
    • topic. Buffer. The identifier which this peer was discovered under.

The info argument is a PeerInfo object, which will emit events of the form info.on('topic', topic => ...) when the multiplex flag is true.

info.ban()

Call this to ban this peer. Makes the swarm stop connecting to it.

info.backoff()

Call this to make the swarm backoff reconnecting to this peer. Can be called multiple times to backoff more.

dropped = info.deduplicate(localIdBuffer, remoteIdBuffer)

Use this method to deduplicate connections.

When two swarms both announce and do lookups on the same topic you'll get duplicate connections between them (one client connection and one server connection each).

If you exchange some sort of peer id between them you can use this method to make DSwarm deduplicate those connection (ie drop one of them deterministically).

If it returns true then this current connection was dropped due to deduplication and is auto removed. Only call this once per connection.

swarm.on('disconnection', (socket, info) => {})

A connection has been dropped.

swarm.connections

A set of all the active connections.

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

A new peer has been discovered on the network and has been queued for connection.

• peer. Object describing the peer.
  • port. Number.
  • host. String. The IP address of the peer.
  • local. Boolean. Is the peer on the LAN?
  • referrer. Object. The address of the node that informed us of the peer.
    • port. Number.
    • host. String. The IP address of the referrer.
    • id. Buffer.
  • topic. Buffer. The identifier which this peer was discovered under.

swarm.on('peer-rejected', (peer) => {})

A peer has been rejected as a connection candidate.

• peer. Object describing the peer.
  • port. Number.
  • host. String. The IP address of the peer.
  • local. Boolean. Is the peer on the LAN?
  • referrer. Object. The address of the node that informed us of the peer.
    • port. Number.
    • host. String. The IP address of the referrer.
    • id. Buffer.
  • topic. Buffer. The identifier which this peer was discovered under.

swarm.on('updated', ({ key }) => {})

Emitted once a discovery cycle for a particular topic has completed. The topic can be identified by the key property of the emitted object. After this event the peer will wait for period of between 5 and 10 minutes before looking for new peers on that topic again.