Ping with socket.io

index.html

<input placeholder="ping something" /><button>ping!</button>
<pre></pre>
<script src="//localhost:8888/socket.io/socket.io.js"></script>
<script>
  (function () {
    var socket = io.connect("//localhost:8888"),
        pre = document.querySelectorAll("pre")[0],
        input = document.querySelectorAll("input")[0],
        button = document.querySelectorAll("button")[0];

    button.addEventListener("click", function () {
        socket.emit('ping', input.value);
    });

    socket.on("pong", function (data) {
        pre.innerHTML += data;
    });
  })();
</script>

server.js

var io = require('socket.io').listen(8888),
    ch = require('child_process');

io.sockets.on('connection', function (socket) {
    socket.on('ping', function (data) {
        var ping = ch.spawn('ping', [data]);
        ping.stdout.on("data", function (data) {
            socket.emit("pong", data.toString());
        });

    });
});