🐦 Sparrow-RTC

🌟 Sparrow makes WebRTC easy.
🚀 Try the demo at https://sparrow.benev.gg/
🤝 WebRTC is peer-to-peer networking between browser tabs.
🎮 Perfect for making player-hosted multiplayer web games.
💪 Self-hostable, read self-hosting.md for instructions.
💖 Free and open source.

🫂 Connecting peers together

The Objective:
Connect two players together, and establish RTC Data Channels between them.

1. Install sparrow-rtc

   npm i sparrow-rtc

2. Host a session

   import Sparrow from "sparrow-rtc"
   
   const sparrow = await Sparrow.host({
   
     // accept people joining, send/receive some data
     welcome: prospect => connection => {
       console.log(`peer connected: ${connection.id}`)
       connection.cable.reliable.send("hello")
       connection.cable.reliable.onmessage = e => console.log("received", m.data)
       return () => console.log(`peer disconnected: ${connection.id}`)
     },
   
     // lost connection to the sparrow signaller
     close: () => console.warn(`connection to sparrow signaller has died`),
   })
   
   // anybody with this invite code can join
   sparrow.invite
     // "215fe776f758bc44"

3. Join that session

   import Sparrow from "sparrow-rtc"
   
   const sparrow = await Sparrow.join({
     invite: "215fe776f758bc44",
     disconnected: () => console.log(`disconnected from host`),
   })
   
   // send and receive data
   sparrow.connection.cable.reliable.send("world")
   sparrow.connection.cable.reliable.onmessage = m => console.log("received", m.data)

🔌 Get the Cable!

• The cable is what you want. The cable is what you need.
• The default cable that sparrow gives you has two RTC Data Channels.
• Each data channel has a channel.send(data) method, so you can send data.
• Each data channel has a channel.onmessage = event => {} function, so you can receive messages.

🦸 cable.reliable — orderly message delivery

• Every message is accounted for. Guaranteed to have no losses (unless a disconnect occurs).
• When a message goes missing — massive catastrophic lag spike, everything halts until the missing message is successfully retransmitted.
• Ideal for important game events like "this player picked up this inventory item" or something like that.

🦹 cable.unreliable — chaotic shouting message shouting

• Not every message will arrive. There will be losses.
• When a message goes missing — it's ignored, and everything continues like nothing happened.
• Ideal for "continuous data" like "now this player is located here" 30 times per second.

🚪 Knock knock, who's there?

• Even when they have your invite code, a user must knock before they can connect.
• The default, is to allow everybody who knocks, like this:

  const sparrow = await Sparrow.host({
  
    // allow everybody
    allow: async() => true,
  })

• Each user has a reputation which is a salted hash of their IP address -- making it easy for you to setup a ban list:

  const myBanList = new Set()
    .add("a332f6646c65f738")
    .add("0d506addf169c407")
  
  const sparrow = await Sparrow.host({
  
    // allow people who are not banned
    allow: async({reputation}) => {
      return !myBanList.has(reputation)
    },
  })

• Hosts can use allow to ban unwanted joiners, but conversely, joiners can ban unwanted hosts:

  const sparrow = await Sparrow.join({
  
    // i want to join this invite i found
    invite: "215fe776f758bc44",
  
    // but not if it's this creep!
    allow: async({reputation}) => reputation !== "a332f6646c65f738",
  })

• You can also use the allow function as a global switch, to just close the door and prevent any more joiners:

  let doorIsOpen = true
  
  const sparrow = await Sparrow.host({
    allow: async() => doorIsOpen,
  })
  
  // Close the door!
  doorIsOpen = false

• And it's async, in case you want to consult your own remote service or something.

👥 How to deal with people

• Okay, so you can pass this kind of welcome function to Sparrow.host. Here's some notes about the connection object you'll get:

  const sparrow = await Sparrow.host({
    welcome: prospect => connection => {
  
      // ephemeral id
      connection.id
  
      // persistent id (based on ip address)
      connection.reputation
  
      // RTCPeerConnection (webrtc internals)
      connection.peer
  
      // the cable you need
      connection.cable
  
      // destroy this connection
      connection.disconnect()
  
      // react to the other side disconnecting
      return () => {}
    },
  })

  • Note, you can also pass a welcome function like this to Sparrow.join, but, you don't have to..
• You can gather some useful connectivity data for each connection with this helper function:

  const report = await Sparrow.reportConnectivity(connection.peer)
  
  report.kind
    // "local" -- connected directly over local area network
    // "direct" -- connected directly over the internet
    // "relay" -- connected via indirect proxy TURN server
  
  report.bytesSent
    // number of bytes sent
  
  report.bytesSent
    // number of bytes received

• Optionally, you can react to prospect, which is an ongoing connection attempt:

  const sparrow = await Sparrow.host({
    welcome: prospect => {
      console.log(`${prospect.id} is attempting to connect..`)
  
      // ephemeral id
      prospect.id
  
      // persistent id (based on ip address)
      prospect.reputation
  
      // RTCPeerConnection (webrtc internals)
      prospect.peer
  
      // react to connection failure
      prospect.onFailed(() => {
        console.log(`${prospect.id} failed to connect`)
      })
  
      // react to successful connection
      return connection => {
        console.log(`${prospect.id} successfully connected`)
  
        // react to disconnected
        return () => {}
      }
    },
  })

  • This isn't necessary, you can just ignore prospects and only concern yourself with connections.
  • Prospects are an opportunity for you to display the activity of attempted connections as they're in progress.

🔗 Custom URLs

• Sparrow.host and Sparrow.join both accept these common options

  import {Sparrow} from "sparrow-rtc"
  
  const sparrow = await Sparrow.host({
    ...myOtherOptions,
  
    // sparrow's official signaller instance (default shown)
    url: "wss://signaller.sparrow.benev.gg/",
  
    // choose which stun and/or turn servers to use (default shown)
    rtcConfigurator: async() => ({
      iceServers: [
  
        // these are free publicly available STUN servers
        {urls: ["stun:stun.l.google.com:19302"]},
        {urls: ["stun:stun.services.mozilla.com:3478"]},
        {urls: ["stun:server2024.stunprotocol.org:3478"]},
  
        // if you pay for a TURN service,
        // you'll obtain some config data that goes in this same array
        // as these STUN servers above.
      ],
    }),
  })

🚦 Understanding Sparrow's Signaller Service

• We host a free official Sparrow signaller for everybody:
  • https://signaller.sparrow.benev.gg/
  • https://signaller.sparrow.benev.gg/health — shows a timestamp if the signaller is up and running
• The Sparrow Signaller does two main things:
  • It helps users find each other via invite links.
  • It negotiates a complex exchange of WebRTC information, to establish connections between users.
• You can self-host your own instance.

⚡ Understanding STUN Servers

• To allow users to connect to each other, they need to know each other's IP addresses.
• WebRTC usees STUN servers to discover the user IP addresses.
• STUN servers are efficient and cheap to operate, and so there are many publicly available free STUN servers you can use.
• By default, Sparrow will use stun servers by google.com, mozilla.com, and stunprotocol.org.

💈 Understanding TURN Servers

• Sometimes users are under network conditions that makes direct connections impossible.
  • This happens because the internet is badly designed.
• To save the day, you can configure a TURN server which will act as a reliable relay for those who are unable to achieve direct connections.
  • On the up side, with a TURN service, your users can basically always connect reliably.
  • On the down side, this costs you money, because you have to pay for all the relayed traffic bandwidth.
  • Sparrow does not offer TURN service for free, you'd need to configure your own.
  • You can run your own TURN server, like coturn, or you can use a paid cloud service provider like Cloudflare's.
  • For some reason these are all a total pain to setup properly.
• To use a TURN server, you just need to include the URL for it in your rtcConfigurator's iceServers.
• Sparrow's signaller does have a little cloudflare integration for my own personal convenience, which you can also take advantage of, but you'd have to self-host the signaller and follow the cloudflare instructions there, to wire it up to your own cloudflare account -- however, you might instead consider spinning up your own coturn TURN server and continue to use the sparrow signaller for free -- either strategy would be a perfectly valid approach.

🔌 Custom Cables

• You can prepare any kinds of RTC Data Channels you like, by establishing your own cableConfig

  // import various helpers
  import {Sparrow, DataChanneler, concurrent} from "sparrow-rtc"
  
  // define your own cable properties (default shown, available as StdCable)
  export type MyCable = {
    reliable: RTCDataChannel
    unreliable: RTCDataChannel
  }
  
  // define your own cable config (default shown)
  const myCableConfig = Sparrow.asCableConfig<MyCable>({
    offering: async peer => {
      return concurrent({
        reliable: DataChanneler.offering(peer, "reliable", {
          ordered: true,
        }),
        unreliable: DataChanneler.offering(peer, "unreliable", {
          ordered: false,
          maxRetransmits: 0,
        }),
      })
    },
    answering: async peer => {
      return concurrent({
        reliable: DataChanneler.answering(peer, "reliable"),
        unreliable: DataChanneler.answering(peer, "unreliable"),
      })
    },
  })

• You can then use your cable config for Sparrow.host and Sparrow.join

    //                    your custom cable type
    //                                 |
  const sparrow = await Sparrow.host<MyCable>({
    ...myOtherOptions,
  
    // your custom cable config
    cableConfig: myCableConfig,
  })

• Note that Sparrow creates its own special utility rtc data channel called the conduit, which is reserved for sparrow internal functionality (it sends "bye" notifications when you call connection.disconnect() to immediately notify the other side)

📜 Logging

• You can specify to only log errors like this

  const sparrow = await Sparrow.join({
    invite: "8ab469956da27aff3825a3681b4f6452",
    disconnected: () => console.log(`disconnected from host`),
  
    // only log errors
    logging: Sparrow.errorLogging,
  })

• Of course you can set this logging option on Sparrow.host as well
• Three available settings are:
  • Sparrow.stdLogging -- log everything (default)
  • Sparrow.errorLogging -- only log errors
  • Sparrow.noLogging -- log nothing at all

💖 Free and open source

• Gimme a star on github!
• Join our Benevolent Discord Community, shout at Chase and say sparrow-rtc is rad!