@openlab/portals
v0.2.1
Published
Portals is a pair of libraries for creating WebRTC connections between multiple parties, a "portal".
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portals.js
Portals is a pair of libraries for creating WebRTC connections between multiple parties, a "portal".
npm install @openlab/portals
portals.js is ESM only.
Server
All connections in a portal are peer-to-peer, but the first step needs a signalling server to establish those connections. Portals provides an agnostic library to perform the signalling and a specific version tailored for Node.js and ws.
Node.js + express + ws
import http from 'http'
import path from 'path'
import url from 'url'
import express from 'express'
import { NodePortalServer } from '@openlab/portals/node-server.js'
const app = express()
.use(express.static(path.dirname(url.fileURLToPath(import.meta.url))))
.use(express.text())
const rooms = ['coffee-chat', 'home', 'misc']
const server = http.createServer(app)
const portal = new NodePortalServer({ server, path: '/portal', rooms })
server.listen(8080, () => console.log('Listening on :8080'))
You'll need to
npm install express ws
to get the dependencies
Client
On the client, there is a library for connecting to the signalling server, connecting to a room and handling connections and disconnections within that room.
import { NodePortalServer } from '@openlab/portals/client.js'
const rtc = {
iceServers: [
{ urls: 'stun:stun1.l.google.com:19302' },
{ urls: 'stun:stun2.l.google.com:19302' },
],
}
async function main() {
// Determine the room to join somehow
const url = new URL(location.href)
const room = url.searchParams.get('room')
// Create a WebSocket URL to the PortalServer
const server = new URL('portal', location.href)
server.protocol = server.protocol.replace(/^http/, 'ws')
// Request a MediaStream from the client's webcam
const stream = await navigator.mediaDevices.getUserMedia({
video: { width: 1280, height: 720 },
})
// Create the portal gun
const portalGun = new PortalGun({ room, url: server, rtc })
portalGun.addEventListener('connection', (portal) => {
// Add the local MediaStream to send video through the portal
// Note: This API is currently unstable
portal.addMediaStream(stream)
// Listen for tracks from the peer to recieve video through the portal
portal.peer.addEventListener('track', (event) => {
event.track.onunmute = () => {
console.debug('@connected', portal.target.id, event.streams[0])
// Render the track somehow
}
})
})
// Stop rendering a peer that has disconnected
portalGun.addEventListener('disconnection', (portal) => {
console.debug('@disconnection', portal.target.id, null)
})
}
main()
You create a PortalGun
which is responsible for talking to the signalling server and telling you about new and closed connections, known as "portals".
When you recieve a new portal, through "connection"
, you pass it the local MediaStream
and listen for tracks that it is sending. Its up to you what to do with those streams.
You have portal.target.id
which is a unique id for that portal.
When a portal closes, through "disconnection"
, you can clean up any rendering you previously did for it.
The rtc
config is directly passed to the constructor of RTCPeerConnection, so you can put any of those parameters in there.
Full example
For a detailed example, see example which is a full use of NodePortalServer
on the backend and PortalGun
on the frontend. The example is a local-cctv like system where any user that joins the room is added to a video-only screen where everyone can see everyone else.
It has a small server-side hack to bundle the client-side code using esbuild.
Agnostic library
If you don't want to use Node.js or want to use different libraries, there is an an agnostic version of the server. Below is an example for hooking up the portals library with a hypothetical socket server. It needs to call these methods at the right times:
onConnection
- when a new socket has connected, it should implementTraveller
onMessage
- when a socket recieved a message from the portals clientonClose
- when a socket disconnected
There are extra hooks for debugging, exposed as events:
error
(Error) - emits when an error occureddebug
(string) - outputs debug messages
import { CustomSocketServer, CustomSocket } from 'custom-socket-lib'
import { PortalServer, Traveller } from '@openlab/portals/server.js'
const portals = new PortalServer({ rooms: ['home'] })
function getConnection(socket: CustomSocket, request: Request): Traveller {
const { id, room } = '/* get from socket */'
function send(type, payload, from) {
socket.send(JSON.stringify({ type, [type]: payload, from }))
}
return { id, room, send }
}
const sockets = new CustomSocketServer(/* ... */)
sockets.addEventListener('connection', (socket) => {
// 1. Tell portals about the new connection
const connection = getConnection(socket)
portals.onConnection(connection)
// 2. Tell portals about new messages
socket.addEventListener('message', (message) => {
const { type, [type]: payload, target = null } = JSON.parse(message)
portals.onMessage(connection, type, payload, target)
})
// 3. Tell portals about connections closing
socket.addEventListener('close', () => {
portals.onClose(connection)
})
})
// Optionally debug things
portals.addEventListener('error', (error) => console.error(error))
portals.addEventListener('debug', (message) => console.debug(message))
You wrap your library's transport into a Traveller
object that the library
will store and use to send messages to clients.
You can get the id
or room
from the connecting client or you can generate them.
The client expects WebSocket messages in a certain format, defined below,
so the send
method should format them in this way.
crypto.randomUUID()
is good for generating client ids.
When a client disconnects you need to tell the PortalServer with onClose
and pass the traveller object.
When a client recieves a message, tell the PortalServer with onMessage
.
The client has a default payload structure, defined below.
client → server messages
The client sends messages up to the server as JSON.
It always has type
as a string, then the "type" is used as a key is used to put the payload in.
target
is optional and may contain the id of the specific client they want to talk to.
{ "type": "ice", "ice": { "key": "value" }, "target": "abcdef" }
On the client, you can pass a composeMessage
method to provide your own format.
server → client messages
The server sends messages down to the client as JSON.
It always has type
as a string, then the "type" is used as a key is used to put the payload in.
from
is optional and may contain the id of the specific client that send the message.
{ "type": "ice", "ice": { "key": "value" }, "from": "abcdef" }
On the client, you can pass a parseMessage
method to parse a custom format your server might use.
Signals
There are types for the different messages that are sent up and down from the server, these are currently in src/lib.ts
InfoSignal
Sent to clients when members join and leave the room. It contains the id of the client, the other members in the room and whether to be "nice" to them or not (used as part of the WebRTC call).
ErrorSignal
When the client did something wrong, it has an error which the client could use to rectify it, or let the developer know what to fix. Error codes:
room_not_set
- sent when a client joined and didn't set the?room
URL parameter.room_not_found
- sent when a client joined, messaged or left with a room that doesn't exist.
DescriptionSignal
Used as part of the WebRTC calling, more info
CandidateSignal
Used as part of the WebRTC calling, more info
Future work / ideas
- designing the server to be horizontally scalable
- can rooms be in redis somehow, or backed by socket.io?
- dynamic rooms / API for existing rooms
- Data connections
- add automated tests
- explore Deno usage
- pull rtc configuration from the server?
- simplify payload structure?
- explore what happens when MediaStreams break
- abstract away from WebSockets?
- what to do with signaller 'disconnection' / 'reconnection' events
- rename current portal events to 'opened' / 'closed' ?
- better name for 'signaller'
Non-goals
- Anything not peer-to-peer or more complicated topologies