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 11 (March 2012)
• IE 10 (September 2012)
• Safari 6 (July 2012)
• Opera 12.1 (November 2012)

From 2013 WebSocket is universally available.

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

Evolution

• RFC 7692 (2015) — permessage-deflate compression
• RFC 8441 (2018) — WebSocket over HTTP/2
• RFC 9220 (2022) — WebSocket over HTTP/3

WebTransport (2021+) on QUIC/HTTP/3 proposes evolution for UDP-like datagrams in browsers, but WebSocket remains the dominant standard.

In the Italian context

WebSocket is at the basis of many Italian real-time applications:

• Fintech and trading (Banca Sella, Fineco, crypto platforms)
• eSports and gaming
• Collaboration (fintech companies, SaaS management software)
• Health monitoring (telemedicine, patient monitoring)

References: RFC 6455 (December 2011). IETF. Ian Fette (Google), Alexey Melnikov. ws://, wss:// schemes. Full browser adoption 2013. Subsequent extensions RFC 7692, RFC 8441 (HTTP/2), RFC 9220 (HTTP/3).