RemoteDocumentMessaging

Overview

This document describes a proposal for discovering and communicating with "remote" documents. In particular, this proposal lets a web page communicate with another document even if the web page does not have a direct script connection to that document.

Use Cases

The user opens the same word processing document hosted by a document editing web site in two different browser windows. The document editing web site wants to ensure that edits in one window a reflected in the other window without needing to round-trip through the server (e.g., because the user is offline). Unfortunately, the documents are in different units of related browsing contexts, which means the two documents cannot form a direct script connection. Using remote document messaging, the two documents can discover each other and update each other about edits performed by the user.

Specification

partial interface Window {
    MessagePort? connectTo(DOMString target);
};

The connectTo method opens a message port to a browsing context with name target within the caller's origin (although not necessarily within the caller's unit of related browsing contexts).

Examples

Listener

window.addEventListener("connect", function(message) {
  // message.source is a MessagePort we can use to talk to the remote message, just like in a shared worker.
  var remote = message.source;
  remote.postMessage("Welcome!");
  // You can call remote.addEventListener("message", ... ) to continue communicating with the remote window.
}, false);

// Naming your window makes you discoverable by other documents in your origin.
window.name = "the-listener";

Sender

var port = window.connectTo("the-listener");

port.addEventListener("message", function(message) {
  if (message.data == "Welcome!")
    alert("Success!);
}, false);

port.start();