Open Source JavaScript WebSocket Libraries

socket.io is a JavaScript library that allows for realtime, bi-directional communication between web clients and servers. It is composed of two parts: a Node.js server and a JavaScript client library that runs in the browser. socket.io is focused on both reliability and speed, delivering an immensely powerful, fast and yet easy to use realtime engine that’s used by just about everyone: from Microsoft Office and Zendesk to hackathon winners and small startups. It’s considered one of the most depended-upon npm modules, and works on every platform, browser or device.

The rpc-websockets library enables developers to easily implement their business logic that includes messaging between users, machines or any devices. It provides a possibility to send and receive JSON data through the WebSocket communication protocol in order to support two-way notification push, running RPC methods and firing any types of event signalling. Only clients can call RPC methods and not vice versa at the moment. Both frontend (HTML/JS-based) and backend (Node.js-based) development environments are supported.

Rhubarb is a lightweight WebSocket library for multiplayer HTML5 games. It is originally designed to be used by the ROYGBIV Engine. However, it can be used outside of ROYGBIV as well. Javascript is slow, therefore we want to have as much main-process-power as we can in order to do game related calculations, graphics rendering and achieving 60 FPS. For multiplayer games achieving 60 FPS gets even more complicated given that transferring data over WebSockets is a slow operation. It also triggers GC activity by copying the transferred data (if JSON is the preferred way), which eventually slows down the main thread as well.

SockJS is a browser JavaScript library that provides a WebSocket-like object. SockJS gives you a coherent, cross-browser, Javascript API which creates a low latency, full duplex, cross-domain communication channel between the browser and the web server. Under the hood SockJS tries to use native WebSockets first. If that fails it can use a variety of browser-specific transport protocols and presents them through WebSocket-like abstractions. SockJS is intended to work for all modern browsers and in environments which don't support the WebSocket protocol, for example, behind restrictive corporate proxies. SockJS-client does require a server counterpart, such as SockJS-node, which is a SockJS server for Node.js. The API should follow HTML5 Websockets API as closely as possible. All the transports must support cross domain connections out of the box. It's possible and recommended to host a SockJS server on a different server than your main web site.

Sockette is a tiny (367 bytes) wrapper around WebSocket that will automatically reconnect if the connection is lost. In addition to attaching additional API methods, Sockette allows you to reuse instances, avoiding the need to redeclare all event listeners. You have direct access to the (current) underlying WebSocket within every EventListener callback.