webrtc P2P

WebRTC Laboratory

Peer-to-peer browser connectivity, taken apart (connecting, calls, streaming, messaging, file transfer, and screen sharing), with deep-dive articles, live de...

CONNECTING CALLS STREAMING MESSAGING FILE TRANSFER SCREEN SHARING P2P

WebRTC opens a direct path between two browsers: audio, video, and data travel peer-to-peer instead of through a relay. This is the whole subject taken apart: six use-case topics, twenty-five deep-dive articles, live demos you can run, an API reference, and multiplayer games that need nothing but a peer connection. Everything here runs STUN-only, with no relay and no media server in the data path.

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Connecting

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How two browsers find each other and open a direct path: signaling, ICE, and NAT traversal. Every other topic sits on top of this one.

Browser Amedia & data Browser Bmedia & data Signaling Servermetadata exchange STUNnetwork discovery Direct SRTP / SCTP tunnel NO SERVER IN THE DATA PATH Offer / Answer IP discovery peer-to-peer data path signaling & discovery (setup only)
ArchitectureThe three engines and the protocol stack, layer by layer. SignalingThe out-of-band offer/answer handshake that bootstraps a connection. ICE & NATHole-punching through firewalls to find a direct path between peers. SecurityMandatory DTLS and SRTP encryption, on by default.

Calls

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One-to-one and group audio and video, from camera capture to negotiated media tracks and on-the-fly adaptation.

Media CapturegetUserMedia, the full constraints model, and choosing a device. Tracks & StreamsTransceivers, direction, and swapping a track with replaceTrack. Audio ProcessingEcho cancellation, Web Audio metering, gain, and mixing. Group CallsMesh versus host-star topologies and where they stop scaling.

Streaming

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One-to-many broadcast over pure peer-to-peer: what it can do, and the honest wall where a server takes over.

Broadcast TopologiesStar fanout and relay trees, with the uplink math at scale. Encoding & AdaptationBitrate, simulcast, and how the browser adapts to the link. Capture & RecordingStream a canvas, and record any track with MediaRecorder.

Messaging & Data

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The RTCDataChannel for arbitrary peer-to-peer data, with reliable or fast delivery and your own wire protocol on top.

Data ChannelsOpening channels, events, binary payloads, and backpressure. Reliability & Flow ControlOrdered, unreliable, and partial modes (and when to pick each). Wire ProtocolsDesigning message framing and dispatch over the channel. MultiplayerAuthoritative-host and hidden-state sync, plus seeded determinism.

File transfer

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Sending files directly between browsers over a data channel: chunking, integrity, and multi-gigabyte transfers without exhausting memory.

ChunkingSlicing a file into messages with a backpressure-aware send loop. Integrity & ResumeSHA-256 verification, acknowledgements, and offset-based resume. Large Files & MemoryStreaming to disk so a multi-GB file never lands in RAM.

Screen sharing

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Capturing a screen, window, or tab with getDisplayMedia, sharing its audio, and combining it with the camera.

Screen CapturegetDisplayMedia, display surfaces, and sending the track. Sharing AudioTab and system audio capture, and mixing it with the mic. LifecycleDetecting the user's Stop, cleanup, and re-sharing. Camera + ScreenSwap, send both, or composite the two into one stream.

See it run

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Minimal, single-purpose demos. Each runs entirely in your browser, peer-to-peer: open one, grant permission, watch the path.

Media demosCamera capture, microphone metering, and a track mixer. Screen demoRoute a window or screen to a remote peer. Streaming demoBroadcast a local track and watch the media path. P2P echoA camera looped back through a real peer connection, in one tab.

Games

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Multiplayer games that push the data channel, server-free. Share a link, play together; nothing routes through a server.

PongAuthoritative-host paddle physics. 2 players. Tic-Tac-ToeThe simplest turn exchange over a data channel. 2 players. BattleshipHidden-state play: only fire/result events cross the wire. 2 players. WormsDestructible terrain over a three-peer host. 2 to 4 players.

Reference & tools

API reference →

The JavaScript API behind it all, live protocol inspectors, and the external specs and libraries worth keeping open.

API referenceRTCPeerConnection, RTCDataChannel, MediaStream and more, each on its own page. Protocol inspectorsRead live ICE candidates, SDP, throughput, and network stats. ResourcesThe official RFCs, specs, and production-hardened libraries.