Implementing Video Chat in a Phoenix Application with WebRTC

The article walks through a basic WebRTC video chat setup in a Phoenix app. Phoenix channels handle the signaling needed before two clients can open a direct peer-to-peer connection, while the browser side uses getUserMedia, RTCPeerConnection, and ICE candidates to move from local stream capture to a working video call.

Reading notes

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• Create a new Phoenix app and route the root path to a call controller that renders a page with local and remote video elements plus Connect, Call, and Hangup buttons.
• Add a call channel with join and message handling, then register that channel in the user socket so clients can join it.
• Include adapter.js in the layout so the WebRTC methods work across browsers.
• In app.js, import the socket, join the call channel, and wire the buttons to connect, call, and hang up.
• The connect action requests local media with getUserMedia and passes the stream to gotStream.
• gotStream stores the local stream, assigns it to the local video element, and calls setupPeerConnection.
• setupPeerConnection creates an RTCPeerConnection, sets callbacks for ICE candidates and remote streams, and adds the local stream to the connection.
• call triggers createOffer, and gotLocalDescription stores the local description and sends it through the channel as signaling data.
• When a remote description arrives, gotRemoteDescription sets it on the peer connection and creates an answer.
• Remote streams are assigned to the remote video element in gotRemoteStream.
• Local ICE candidates are sent through the channel, and incoming ICE candidates are added to the peer connection in gotRemoteIceCandidate.
• The channel message handler parses incoming payloads and decides whether to pass them to gotRemoteDescription or gotRemoteIceCandidate.
• hangup closes the peer connection and resets the page state.
• The post ends by saying that opening two tabs, connecting in both, and calling from one tab should produce a video chat session.