About

WebSockets (or WebSocket) is an API and a protocol for bi-directional, full-duplex communication over TCP sockets. The WebSockets API was originally part of the HTML5 standard, but it has been split off into a separate W3C standard. The WebSockets protocol is an IETF standard described in RFC 6455.

WebSockets has native implementations that are enabled by default in Chrome 4, Safari 5, and iOS 4.2. Firefox 4, and Opera 11 also have WebSockets built-in, but it was disabled by default until a fix in Firefox 6. Other browsers can support WebSockets using a Flash based fallback.

WebSockets supports both unencrypted and encrypted connections. Unencrypted connections use the "ws://" URL scheme and default to port 80. Encrypted connections use the "wss://" URL scheme and default to port 443. Encrypted connections use Transport Layer Security (TLS).

Simple WebSockets browser JavaScript example:

if ("WebSocket" in window) {
    var ws = new WebSocket("ws://echo.websocket.org/");
    ws.onopen = function() {
        console.log("WebSockets connection opened");
        ws.send("a test message");
    }
    ws.onmessage = function(e) {
        console.log("Got WebSockets message: " + e.data);
    }
    ws.onclose = function() {
        console.log("WebSockets connection closed");
    }
} else {
    // No native support
}

Useful Links

• Websockets echo server
• Chromium blog WebSockets announcement
• Socket.IO: a JavaScript client and server (Node.js) library that provides cross-browser communication with automatic fall-back to the best supported method.
• websockify: a WebSockets to generic TCP sockets proxy/bridge. Three implementations for reference: Python, C, and Node.js.
• WebSockets vs BOSH/Channel API
• WebSockets browser and server support: Stack Overflow answer, caniuse.com list