• Autobahn tests all pass.
• Significantly outperforms WebSocket , libwebsockets, Beast, Crow, Gorilla, Kaazing Gateway, ws and Socket.IO in every tested dimension (see benchmark table below).
• Outperforms Node.js itself by 5x in HTTP requests/second when run as a Node.js module.
• Linux, OS X & Windows support.
• Valgrind / AddressSanitizer clean.
• Built-in load balancing and multi-core scalability.
• SSL/TLS support & integrates with foreign HTTPS servers.
• Permessage-deflate built-in.
• Node.js binding exposed as the well-known ws interface (uws is at least 20x faster and 20x more scalable).

Benchmarks are run with default settings in all libraries, except for ws which is run with the native performance addons. These results were achieved with the native C server, not the Node.js addon. Expect worse performance and scalability when using Node.js (don't worry, the Node.js addon will run circles around ws).

µWebSockets is a high performance C library with optional bindings to Node.js. It is greatly recommended investing in a proper C implementation if performance and memory scalability is considered critical for the solution in whole. The C interface has been designed for simplicity and only requires you to write a few lines of code to get a working server:

#include <uWS.h>

int main()
{
    uWS::Hub h;

    h.onMessage([](uWS::WebSocket<uWS::SERVER> ws, char *message, size_t length, uWS::OpCode opCode) {
        ws.send(message, length, opCode);
    });

    h.listen(3000);
    h.run();
}

We built µWS with the existing Node.js infrastructure in mind. That's why we target the widespread ws interface, allowing us to seamlessly integrate with already existing projects. You simply swap require('ws') with require('uws'):

var WebSocketServer = require('uws').Server;
var wss = new WebSocketServer({ port: 3000 });

function onMessage(message) {
    console.log('received: '   message);
}

wss.on('connection', function(ws) {
    ws.on('message', onMessage);
    ws.send('something');
});

There are some important incompatibilities with ws though, we aim to be ~90% compatible but will never implement behavior that is deemed too inefficient:

• Binary data is passed zero-copy as an ArrayBuffer. This means you need to copy it to keep it past the callback. It also means you need to convert it with Buffer.from(message) if you expect a Node.js Buffer.
• webSocket._socket is not a net.Socket, it is just a getter function with very basic functionalities.
• webSocket._socket.remote... might fail, you need to cache it at connection.
• webSocket acts like an EventEmitter with one listener per event maximum.
• webSocket.upgradeReq is only valid during execution of the connection handler. If you want to keep properties of the upgradeReq for the entire lifetime of the webSocket you better attach that specific property to the webSocket at connection.

µWS is already the default engine in recent versions of deepstream.io and SocketCluster.

You can enable uws in Socket.IO using something like this:

var io = require('socket.io')(80);
io.engine.ws = new (require('uws').Server)({
    noServer: true,
    perMessageDeflate: false
});

You can set 'uws' as transformer in Primus:

var primus = new Primus(server, { transformer: 'uws' });

• Node.js 4.x, 5.x & 6.x supported (Windows version requires Node.js 6.4.0 )
• Linux, Mac OS X & Windows supported
• gcc >= 4.8.0 and make (or compatible) are required to build from source. This translates to Visual Studio >= 2015 on Windows and Clang >= 3.3 on macOS.

On installation, the module will be attempted to be build from source. If that fails, it will attempt to fall back to prebuilt modules which are provided for most platforms. If that fails too, uws will throw on require.

First of all you need to install the required dependencies. On Unix systems this is typically done via package managers, like homebrew in the case of OS X or dnf in the case of Fedora Linux. On Windows you need to search the web for pre-compiled binaries or simply compile the dependencies yourself.

• libuv 1.3
• OpenSSL 1.0.x
• zlib 1.x
• CMake 3.x

Obviously you will need to clone this repo to get the sources. We use CMake as build system.

• git clone https://github.com/uWebSockets/uWebSockets.git && cd uWebSockets
• cmake .

Now, on Unix systems it should work by simply running make. Run [sudo] make install as you wish.

If you are running Windows you should now have a bunch of Visual Studio project files and one solution file. Open the solution file, now you need to make sure the header include paths and library paths are all set according to where you installed the dependencies. You might also need to change the names of the libraries being linked against, all according to the names of the installed library files. You know the drill.