broadcast.js

var WsServer = require('ws').Server;
var ws = new WsServer({host: 'localhost', port: 9005});
var con = {
    clientLen : function() {
        return ws.clients.length;
    },
    broadcast: function(msg) {
        ws.clients.forEach(function(client) {
            client.send(JSON.stringify(msg));
        });
    }
}

ws.on('connection', function(socket) {
    socket.on('message', function(message) {
        try {
            var msg = JSON.parse(message);
            con.broadcast(msg);
        } catch (e) {
            socket.send('JSONで送ってください');
        }
    });
});

index.html

<input id="msg"><button id="send">送信</button>
<div id="chat"></div>
<script>
var ws = new WebSocket('ws://localhost:9005');
ws.onmessage = function(msg) {
    chat.innerHTML += '<hr>' + JSON.parse(msg.data);
}
send.onclick = function() {
    ws.send(JSON.stringify(msg.value));
}
</script>