Comm system responsibilities
Besides providing a proxy handler to send messages, a comm system must do these things, if their conditions arise:
- If a reference becomes broken, respond to all __whenBroken messages it received.
- If a remote promise becomes more resolved (including becoming broken), respond to all __whenMoreResolved messages it received.
- Ensure that two separately-created proxies for the same remote reference are the same, or that only one proxy per reference is created (the exact means depends on the proxy maker being used).