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web-udp is a library used to establish unreliable data channels in Node/browser environments. The key goal of this project to provide a small, stable API that anyone can use to work with real-time data on the Web.

The library is currently implemented as an abstraction on top of unordered and unreliable RTCDataChannels. Since WebRTC is a dependency, a WebSocket based signaling server is included with the package to facilitate connections between clients. Client/server connections are available with the help of thewrtc package.

Signal<T>.subscribe(subscriber:T=>any)Signal<T>.unsubscribe(subscriber:T=>any)Client(options?:{url?:string})Client.connect(to?:string="__MASTER__",options?:{binaryType?:"arraybuffer"|"blob",maxRetransmits?:number,maxPacketLifeTime?:number,metadata?:any,UNSAFE_ordered?:boolean}):Promise<Connection>Client.route():Promise<string>Client.connections:Signal<Connection>Connection.send(message:any):voidConnection.close():voidConnection.closed:SignalConnection.errors:Signal<{err:string}>Connection.messages:Signal<any>Connection.metadata:any// NodeServer({server:http.Server,keepAlivePeriod?:number=30000})Server.client():ClientServer.connections:Signal<Connection>

npm i @web-udp/clientnpm i @web-udp/server

Below is a simple example of a ping server:

// client.jsimport{Client}from"@web-udp/client"asyncfunctionmain(){constudp=newClient()constconnection=awaitudp.connect()connection.send("ping")connection.messages.subscribe(console.log)}

// server.jsconstserver=require("http").createServer()const{ Server}=require("@web-udp/server")constudp=newServer({ server})udp.connections.subscribe(connection=>{connection.messages.subscribe(message=>{if(message==="ping"){connection.send("pong")}})connection.closed.subscribe(()=>console.log("A connection closed."))connection.errors.subscribe(err=>console.log(err))})server.listen(8000)

Themetadata option inClient.connect is used to send arbitrary handshake data immediately after establishing a connection. When a new connection is established, the remote client can access this data on themetadata property of the connection object without having to subscribe to the remote client's messages. Handshake metadata is transmitted over a secureRTCDataChannel, making it a good candidate for sensitive data like passwords.

In the below example, a server handles authentication before subscribing to the client's messages:

// client.jsconstconnection=awaitudp.connect({metadata:{credentials:{username:"foo",password:"bar",},},})

// server.jsudp.connections.subscribe(connection=>{letusertry{user=awaitfakeAuth.login(connection.metadata.credentials)}catch(err){// Authentication failed, close connection immediately.connection.send(fakeProtocol.loginFailure())connection.close()return}// The user authenticated successfully.connection.send(fakeProtocol.loginSuccess(user))connection.messages.subscribe(...)})

web-udp also supports peer-to-peer communication. The below example demonstrates two clients connected in the same browser tab:

<!-- index.html --><scriptsrc="/node_modules/@web-udp/client/dist/index.js"></script><scriptsrc="client.js"></script>

// client.jsasyncfunctionmain(){constleft=newUdp.Client()constright=newUdp.Client()constroute=awaitleft.route()constconnection=awaitright.connect(route)left.connections.subscribe(connection=>connection.messages.subscribe(console.log),)connection.send("HELLO")}

// server.jsconstserver=require("http").createServer()const{ Server}=require("@web-udp/server")Server({ server})server.listen(8000)

Client.connect optionally takes the RTCDataChannelmaxPacketLifeTime andmaxRetransmits options. These options can be used to enable an unordered and reliable data channel.

WebSockets are used as the signaling transport. This socket is kept open after the DataChannel is established to forward it's close event (e.g. when a browser tab is closed) in order to terminate hangingweb-udp connections. A keepalive signal is sent periodically to keep the socket open in the case of hosts with connection timeouts. The period at which the keepalive signal is sent can be configured via the server'skeepAlivePeriod option.

Copyright 2023 Eric McDaniel

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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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