Using WebSocket for file transfer

Question

One of my university lecturers pointed out that it would be interesting to see WebSockets used for file transfer. I'd imagine it would be possible to decode and encode an image file using base64, however would it be possible to send JavaScript / CSS files via WebSocket?

The server i'm using is Node.js, and my browser is Google Chrome 16.

score 8 · Accepted Answer · answered Feb 10 '12 at 15:06

Yes. You can send JavaScript and CSS via WebSockets (or AJAX for that matter). You also shouldn't need to base64 encode the CSS and JavaScript like you would an image as long as the WebSocket server is properly UTF-8 encoding any special Unicode characters in the Javascript.

Once you have received the Javascript or CSS via WebSocket, you can load them using the following mechanism (where type is either 'script' or 'css'):

function dynamic_load(type, content) {
    var elem = document.createElement(type);
    elem.type = (type === 'script') ? 'text/javascript' : 'text/css';
    elem.innerHTML = content;
    document.getElementsByTagName("head")[0].appendChild(elem);
}

That mechanism may have trouble in IE 8 and earlier but since you are using WebSockets I suspect your target is modern browsers. You can verify that the dynamic_load function works from your browser's Javascript console:

dynamic_load('script', "alert('hello world');");

You can send anything and everything. There's nothing you can't send, even viruses. — Pacerier, Mar 16 '15 at 13:49
This includes it as a script tag.. is there a way to use it a a regural file ? So we could transfer over wss and call — Abd-Elaziz Sharaf, Jan 01 '23 at 00:51

score 1 · Answer 2 · answered Feb 11 '12 at 15:37

My node.js ws library handles file sends -- even binary ones. Check out one of the examples here, which does uploads: https://github.com/einaros/ws/tree/master/examples/fileapi

Rather than using websockets for receiving the webpage assets (scripts, css, images, etc), however, I'd recommend sticking with SPDY -- which was intentionally crafted for that very purpose. Node.js has spdy-support, by the way (see https://github.com/indutny/node-spdy).

SPDY is deprecated and will be removed soon. – Pacerier Mar 16 '15 at 13:49 — Pacerier, Mar 16 '15 at 13:49

Using WebSocket for file transfer

2 Answers2