Building a Minimal WebRTC Peer Without a Signaling Server (Using Only Manual SDP Exchange)

Most WebRTC tutorials gloss over the signaling step by abstracting it into a backend service — but what if you don’t want a signaling server at all? In this post, we’ll walk through a minimal WebRTC peer-to-peer connection that works entirely through manual SDP exchange. This is useful for testing, debugging, or building offline/local tools where centralized signaling isn’t feasible. Setup All you need is a modern browser. We’ll create two peers manually in separate tabs or devices and copy-paste their session descriptions (SDP) between them. This is pure HTML + JavaScript. No frameworks, no backends, no servers. Full Working Code Local SDP (copy this to remote) Remote SDP (paste from other peer) Set Remote Description const pc = new RTCPeerConnection(); pc.onicecandidate = (e) => { if (e.candidate === null) { document.getElementById('local').value = JSON.stringify(pc.localDescription); } }; pc.ondatachannel = (event) => { const receiveChannel = event.channel; receiveChannel.onmessage = (e) => console.log("Received:", e.data); receiveChannel.onopen = () => receiveChannel.send("Hello from receiver!"); }; const channel = pc.createDataChannel("chat"); channel.onopen = () => channel.send("Hello from initiator!"); channel.onmessage = (e) => console.log("Received:", e.data); pc.createOffer().then(offer => pc.setLocalDescription(offer)); window.connect = () => { const remoteSDP = JSON.parse(document.getElementById('remote').value); pc.setRemoteDescription(new RTCSessionDescription(remoteSDP)); }; Explanation This example creates a WebRTC data channel between two peers without using a signaling server. The createDataChannel method opens a bidirectional channel, and the SDP offer/answer handshake is done manually by copy-pasting the session descriptions between the peers. Each browser must have its own copy of the page open. One peer creates an offer and sends it manually to the other. The second peer parses that SDP and responds with an answer. After both peers set their remote descriptions, ICE candidates complete the connection and the data channel opens. Pros & Cons ✅ Pros Zero infrastructure — just use two browsers Great for debugging and learning internals Full control of the signaling process Useful for P2P local or air-gapped use cases ⚠️ Cons Not scalable — copy-paste doesn’t work in production ICE may fail across NATs without TURN/STUN servers Still requires an internet stack and modern browser support No encryption handshake beyond WebRTC defaults Summary If you've ever wanted to peek under the hood of WebRTC without relying on third-party signaling servers or frameworks, this pattern gives you total transparency and control. Perfect for offline dev tools, debugging, or side-channel communication setups. If this was useful, you can Buy Me a Coffee ☕

Apr 22, 2025 - 21:47

Building a Minimal WebRTC Peer Without a Signaling Server (Using Only Manual SDP Exchange)

Most WebRTC tutorials gloss over the signaling step by abstracting it into a backend service — but what if you don’t want a signaling server at all? In this post, we’ll walk through a minimal WebRTC peer-to-peer connection that works entirely through manual SDP exchange. This is useful for testing, debugging, or building offline/local tools where centralized signaling isn’t feasible.

Setup

All you need is a modern browser. We’ll create two peers manually in separate tabs or devices and copy-paste their session descriptions (SDP) between them.

This is pure HTML + JavaScript. No frameworks, no backends, no servers.

Full Working Code







  Local SDP (copy this to remote)


  

Remote SDP (paste from other peer)

Explanation

This example creates a WebRTC data channel between two peers without using a signaling server. The createDataChannel method opens a bidirectional channel, and the SDP offer/answer handshake is done manually by copy-pasting the session descriptions between the peers.

Each browser must have its own copy of the page open. One peer creates an offer and sends it manually to the other. The second peer parses that SDP and responds with an answer. After both peers set their remote descriptions, ICE candidates complete the connection and the data channel opens.

Pros & Cons

✅ Pros

Zero infrastructure — just use two browsers
Great for debugging and learning internals
Full control of the signaling process
Useful for P2P local or air-gapped use cases

⚠️ Cons

Not scalable — copy-paste doesn’t work in production
ICE may fail across NATs without TURN/STUN servers
Still requires an internet stack and modern browser support
No encryption handshake beyond WebRTC defaults

Summary

If you've ever wanted to peek under the hood of WebRTC without relying on third-party signaling servers or frameworks, this pattern gives you total transparency and control. Perfect for offline dev tools, debugging, or side-channel communication setups.

If this was useful, you can Buy Me a Coffee ☕