Can socket.io work across domains?

I have a socket.io implementation, and I'm trying to make it work across domains but it appears it can't. Here's my exact use case:

• I have a node.js server running socket.io.
• I have a JS / HTML5 game that I want to be able to host from anywhere, which has the client socket.io code and tries to connect to the server.
• I have the same JS code running on mobile devices via SpiderMonkey (this is one of the main reasons I need to run this from any domain).

I find that I simply cannot connect to the socket unless I am serving the JS code from my node.js server to a browser. If I simply open the HTML file on my disk from my browser, for example, it will not work.

Server code:

io.on( "connection", function( socket )
    {
        this.socket = socket;
        this.socket.on( "echo", function( str ){ this.socket.emit( "message", str ); }.bind( this ) );
    }.bind( this ) );

Client code:

this.socket = io.connect( ip );
this.socket.on("message", function( str ) { console.log( str ); } );

And I can't even connect, I get my print out that it's trying to connect, but it never succeeds and then starts throwing ping errors. So, is this even possible? Or must I do it with long polling or something?

The error:

[Error] Failed to load resource: A server with the specified hostname could not be found. (socket.io, line 0)

EXTRA INFO: This specifically will not work if I am trying to connect from an HTML file opened from disk using file:///. I am going to try across different machines on the same network...