GET http://localhost:8080/socket.io/?EIO=2&transport=polling&t=1409325689935-6 net::ERR_CONNECTION_REFUSED

socket = io.connect(document.domain, {
    'sync disconnect on unload' : false
});

<script type="text/javascript" onload="loaded()" src="get_socket.js"></script>

function loaded(){

//this will only execute if the server is up

}

var load,execute,loadAndExecute;
load=function(a,b,c){var d;d=document.createElement("script"),d.setAttribute("src",a),b!=null&&d.addEventListener("load",b),c!=null&&d.addEventListener("error",c),document.body.appendChild(d);return d},
execute=function(a){var b,c;typeof a=="function"?b="("+a+")();":b=a,c=document.createElement("script"),c.textContent=b,document.body.appendChild(c);return c},
loadAndExecute=function(a,b,c){return load(a,function(){return execute(b)},function(){return c();})};

loadAndExecute("domain.com:80/socket.io/socket.io.js", function() {
    //it loaded, put main code here
},
function(){
    //failed to load, put error display code here
});