WebSocket RFC 6455: the protocol for real-time web

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The limit of polling

Before WebSocket, “real-time” communication between browser and server is achieved with workarounds:

• Short polling — client repeats HTTP requests every N seconds
• Long polling — HTTP request held open until event
• Comet — HTTP streaming techniques
• Server-Sent Events (2006-2009) — unidirectional server→client

None is efficient for bidirectional low-latency communication (chat, trading, gaming, live dashboard).

The release

RFC 6455 is published by the IETF in December 2011. Main authors: Ian Fette (Google), Alexey Melnikov. The protocol had been introduced in draft in 2008 by Ian Hickson (HTML5 spec) and Michael Carter.

The final draft is worked on by a working group including browser vendors, Apache Foundation, other implementers.

How it works

1. HTTP Upgrade handshake — client sends GET with Upgrade: websocket header
2. Server responds 101 Switching Protocols
3. Persistent TCP connection — after handshake, binary WebSocket frames
4. Framing — text/binary/close/ping/pong frames with client→server masking
5. URI scheme — ws:// (plaintext) or wss:// (TLS)

const ws = new WebSocket('wss://api.example.com/stream');
ws.onmessage = (e) => console.log(e.data);
ws.send(JSON.stringify({ action: 'subscribe' }));

Browser adoption

• Chrome 14 (September 2011) — final support
• Firefox — support expected in the 2012 releases
• Safari — on the WebKit roadmap

Universal availability is expected by the second half of 2012 as these browsers ship.

Libraries and frameworks

The protocol is rapidly adopted:

• Socket.IO (2010, fallback for legacy browsers)
• ws — Node.js library, faster
• Phoenix Channels (Elixir)
• SignalR (.NET)
• Django Channels (Python)
• ActionCable (Rails 5)
• Spring WebSocket (Java)

Use cases

• Chat — Slack, Discord, WhatsApp Web
• Trading — real-time orderbook, live prices
• Gaming — online multiplayer
• Collaboration — Google Docs, Figma, Notion
• Live dashboard — monitoring, observability
• IoT — telemetry, remote control
• Push notifications — web apps

In the Italian context

WebSocket is positioning itself as the foundation for Italian real-time applications: fintech and online trading, health monitoring, SaaS collaboration and online gaming are starting to design architectures around a persistent bidirectional channel.

References: RFC 6455 (December 2011). IETF. Ian Fette (Google), Alexey Melnikov. ws://, wss:// schemes.