How to Build a WebRTC App from Scratch

Last updated 2026-07-12

A complete walkthrough of building a WebRTC application from scratch — the signaling, peer connections, NAT traversal, and data channels. The same architecture openbnet manages for you, explained so you understand what happens under the hood.

What you will learn

WebRTC is powerful but complex: signaling, SDP, ICE, STUN/TURN, tracks, data channels. This guide walks through each piece so you understand the full picture — and why a managed platform like openbnet abstracts the hard parts.

Step 1: Set up the signaling server

Every WebRTC app needs a signaling server — a relay for the connection handshake. The signaling server does not handle media; it only forwards SDP offers/answers and ICE candidates. A minimal signaling server is a WebSocket server that routes JSON messages between peers by room or user ID.

// Minimal signaling server (Node.js + ws)
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (ws, req) => {
  ws.on('message', (raw) => {
    const msg = JSON.parse(raw);
    // Forward signaling messages to the target user
    if (msg.type === 'direct-signal') {
      const target = clients.get(msg.payload.target_user_id);
      if (target) target.send(raw);
    }
  });
});

Step 2: Create the RTCPeerConnection

Each peer creates an RTCPeerConnection configured with ICE servers (STUN for candidate discovery, TURN for relay fallback). Local media tracks are added so they will be sent to the remote peer.

const pc = new RTCPeerConnection({
  iceServers: [
    { urls: 'stun:stun.l.google.com:19302' },
    { urls: 'turn:your-turn-server.com', username: 'user', credential: 'pass' }
  ]
});

const stream = await navigator.mediaDevices.getUserMedia({ video: true, audio: true });
stream.getTracks().forEach(t => pc.addTrack(t, stream));

Step 3: The offer/answer handshake

The caller creates an offer, sets it as local description, sends it through signaling. The callee receives it, sets it as remote description, creates an answer, sends it back. The caller sets the answer as remote description. Now both peers know what media to exchange.

Step 4: ICE candidate exchange

As the peer connection gathers network paths, onicecandidate fires. Each candidate is sent through the signaling server. The remote peer calls addIceCandidate. When a working path is found, the connection establishes and media flows directly peer-to-peer.

Step 5: Optional — Data Channels

WebRTC is not just audio/video. Data Channels let you send arbitrary binary/text data peer-to-peer with the same low latency — useful for file transfer, gaming state, or collaborative editing. Create a data channel on the offerer side; it arrives on the answerer side via ondatachannel.

// Offerer creates a data channel
const channel = pc.createDataChannel('file-transfer');
channel.onopen = () => channel.send('Hello peer!');

// Answerer receives it
pc.ondatachannel = (e) => {
  e.channel.onmessage = (msg) => console.log('Received:', msg.data);
};

Production considerations

• TURN server: you need one — ~20% of connections cannot use STUN alone
• Reconnection: handle network changes (WiFi → cellular) with ICE restart
• Group calls: mesh only works to ~10 participants; use an SFU beyond that
• Monitoring: use getStats() for bitrate, packet loss, jitter
• Security: WebRTC encrypts media (DTLS/SRTP), but signaling must use WSS

Why a managed platform helps

Building WebRTC from scratch teaches you the architecture — but running it in production means operating TURN servers, handling ICE restarts, scaling the signaling server, and debugging NAT edge cases. openbnet manages all of this: a WebSocket signaling server, STUN/TURN relay, mesh video calling, and SDKs. Explore the Video & Voice Calling product to see how much easier it is.

Related

• <a href="https://openbnet.com/products/video">Video &amp; Voice Calling product</a>
• <a href="https://openbnet.com/products/signaling">Signaling Server product</a>
• <a href="https://openbnet.com/learn/webrtc-explained">WebRTC Explained</a>
• <a href="https://openbnet.com/learn/what-is-a-signaling-server">What is a Signaling Server</a>

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