Marron: A Firefox Extension for Peer-to-Peer Webapps

By Travis Fischer and Tim O'Donnell

Marron is an extension for Firefox that allows the clients using a web application to pass messages to each other, without server involvement. It was written to investigate the plausability of peer-to-peer web applications.

What's this good for? Allowing the client code of a webapp to talk directly to other client code without using the server has some interesting implications, including:

• Decreasing server load.
• Enhancing privacy, if the webapp is carefully constructed to do so. If certain data is never sent to the server, the user doesn't have to trust the server not to store it. (Of course, the user still has to trust the webapp not to send the data to the server in the first place, but the user can always inspect client code to check for this.)
• Eliminating the server altogether. Combining Marron with software such a Google Gears to save local state, it's possible to write P2P webapps that don't require a server!

Brief Documentation

Install the extension and include marron.js in your webapp's JS. This creates a window.Marron wrapper object that exposes the Marron extension's functionality in a convenient API. If for some reason you'd like to use the extension directly, take a look at the window.marron object the extension exposes.

The window.Marron.register(lambda) function registers a user-provided (object -> void) JS function, lambda, to be called when a message is sent to the newly-created local Marron server, with the contents of the message as its parameter. register() returns a string containing the URL that other clients can pass to window.Marron.send() to send such a message. For example,

var receiveFunction = function (message) {
  alert("Received: " + message);
}
var url = window.Marron.register(receiveFunction);

The window.Marron.send(ur, object) function sends a message to the Marron server running at the given url. The message contents are an arbitrary JS object, object. Since object is JSON-encoded for transfer, functions are not automatically preserved across the wire. Take a look at Function:toString if you need to send objects containing functions. send() returns true if the message was successfully sent (which does not assure receipt), and false if a problem occurred while sending.

Let's continue the above example and append the following code:

window.Marron.send(url, "hello");

Executing this will cause an alert box to appear with the string "Received: hello".

Download

Marron is Free software licensed under the GPL.

To install Marron, download the Marron Extension.

To hack Marron, download the code.