connection

interface-connection

This is a test suite and interface you can use to implement a connection. The connection interface contains all the metadata associated with it, as well as an array of the streams opened through this connection. In the same way as the connection, a stream contains properties with its metadata, plus an iterable duplex object that offers a mechanism for writing and reading data, with back pressure. This module and test suite were heavily inspired by abstract-blob-store and interface-stream-muxer.

The primary goal of this module is to enable developers to pick, swap or upgrade their connection without losing the same API expectations and mechanisms such as back pressure and the ability to half close a connection.

Publishing a test suite as a module lets multiple modules ensure compatibility since they use the same test suite.

Usage

Connection

Before creating a connection from a transport compatible with libp2p it is important to understand some concepts:

• socket: the underlying raw duplex connection between two nodes. It is created by the transports during a dial/listen.
• multiaddr connection: an abstraction over the socket to allow it to work with multiaddr addresses. It is a duplex connection that transports create to wrap the socket before passing to an upgrader that turns it into a standard connection (see below).
• connection: a connection between two peers that has built in multiplexing and info about the connected peer. It is created from a multiaddr connection by an upgrader. The upgrader uses multistream-select to add secio and multiplexing and returns this object.
• stream: a muxed duplex channel of the connection. Each connection may have many streams.

A connection stands for the libp2p communication duplex layer between two nodes. It is not the underlying raw transport duplex layer (socket), such as a TCP socket, but an abstracted layer that sits on top of the raw socket.

This helps ensuring that the transport is responsible for socket management, while also allowing the application layer to handle the connection management.

Test suite

const tests = require('libp2p-interfaces/src/connection/tests')
describe('your connection', () => {
  tests({
    // Options should be passed to your connection
    async setup (options) {
      return YourConnection
    },
    async teardown () {
      // cleanup resources created by setup()
    }
  })
})

API

Connection

A valid connection (one that follows this abstraction), must implement the following API:

• type: Connection

new Connection({
  localAddr,
  remoteAddr,
  localPeer,
  remotePeer,
  newStream,
  close,
  getStreams,
  stat: {
    direction,
    timeline: {
      open,
      upgraded
    },
    multiplexer,
    encryption
  }
})

• <Multiaddr> conn.localAddr
• <Multiaddr> conn.remoteAddr
• <PeerId> conn.localPeer
• <PeerId> conn.remotePeer
• <Object> conn.stat
• <Map> conn.registry
• Array<Stream> conn.streams
• Promise<object> conn.newStream(Array<protocols>)
• <void> conn.removeStream(id)
• <Stream> conn.addStream(stream, protocol, metadata)
• Promise<> conn.close()

It can be obtained as follows:

const { Connection } = require('interface-connection')

const conn = new Connection({
  localAddr: maConn.localAddr,
  remoteAddr: maConn.remoteAddr,
  localPeer: this._peerId,
  remotePeer,
  newStream,
  close: err => maConn.close(err),
  getStreams,
  stats: {
    direction: 'outbound',
    timeline: {
      open: maConn.timeline.open,
      upgraded: Date.now()
    },
    multiplexer,
    encryption
  }
})

Creating a connection instance

• JavaScript - const conn = new Connection({localAddr, remoteAddr, localPeer, remotePeer, newStream, close, getStreams, direction, multiplexer, encryption})

Creates a new Connection instance.

localAddr is the optional multiaddr address used by the local peer to reach the remote. remoteAddr is the optional multiaddr address used to communicate with the remote peer. localPeer is the PeerId of the local peer. remotePeer is the PeerId of the remote peer. newStream is the function responsible for getting a new muxed+multistream-selected stream. close is the function responsible for closing the raw connection. getStreams is the function responsible for getting the streams muxed within the connection. stats is an object with the metadata of the connection. It contains:

• direction is a string indicating whether the connection is inbound or outbound.
• timeline is an object with the relevant events timestamps of the connection (open, upgraded and closed; the closed will be added when the connection is closed).
• multiplexer is a string with the connection multiplexing codec (optional).
• encryption is a string with the connection encryption method identifier (optional).
• status is a string indicating the overall status of the connection. It is one of ['open', 'closing', 'closed']

Create a new stream

• JavaScript - conn.newStream(protocols)

Create a new stream within the connection.

protocols is an array of the intended protocol to use (by order of preference). Example: [/echo/1.0.0]

It returns a Promise with an object with the following properties:

{
  stream,
  protocol
}

The stream property contains the muxed stream, while the protocol contains the protocol codec used by the stream.

Add stream metadata

• JavaScript - conn.addStream(stream, { protocol, ...metadata })

Add a new stream to the connection registry.

stream is a muxed stream. protocol is the string codec for the protocol used by the stream. Example: /echo/1.0.0 metadata is an object containing any additional, optional, stream metadata that you wish to track (such as its tags).

Remove a from the registry

• JavaScript - conn.removeStream(id)

Removes the stream with the given id from the connection registry.

id is the unique id of the stream for this connection.

Close connection

• JavaScript - conn.close()

This method closes the connection to the remote peer, as well as all the streams muxed within the connection.

It returns a Promise.

Connection identifier

• JavaScript - conn.id

This property contains the identifier of the connection.

Connection streams registry

• JavaScript - conn.registry

This property contains a map with the muxed streams indexed by their id. This registry contains the protocol used by the stream, as well as its metadata.

Remote peer

• JavaScript - conn.remotePeer

This property contains the remote peer-id of this connection.

Local peer

• JavaScript - conn.localPeer

This property contains the local peer-id of this connection.

Get the connection Streams

• JavaScript - conn.streams

This getter returns all the muxed streams within the connection.

It returns an Array.

Remote address

• JavaScript - conn.remoteAddr

This getter returns the remote multiaddr address.

Local address

• JavaScript - conn.localAddr

This getter returns the local multiaddr address.

Stat

• JavaScript - conn.stat

This getter returns an Object with the metadata of the connection, as follows:

• status:

This property contains the status of the connection. It can be either open, closing or closed. Once the connection is created it is in an open status. When a conn.close() happens, the status will change to closing and finally, after all the connection streams are properly closed, the status will be closed. These values can also be directly referenced by importing the status file:

const {
  OPEN, CLOSING, CLOSED
} = require('libp2p-interfaces/src/connection/status')

if (connection.stat.status === OPEN) {
  // ...
}

• timeline:

This property contains an object with the open, upgraded and close timestamps of the connection. Note that, the close timestamp is undefined until the connection is closed.

• direction:

This property contains the direction of the peer in the connection. It can be inbound or outbound.

• multiplexer:

This property contains the multiplexing codec being used in the connection.

• encryption:

This property contains the encryption method being used in the connection. It is undefined if the connection is not encrypted.

Tags

• JavaScript - conn.tags

This property contains an array of tags associated with the connection. New tags can be pushed to this array during the connection's lifetime.