See "Using MessageChannel() bidirectionally for multiple messages between page and iframe" stackoverflow and "An Introduction to HTML5 Web Messaging" page
See also "What's difference between web-messaging with MessageChannel and without?" stackoverflow
//wiki.ralfbarkow.ch/assets/pages/i-directional-multimessage-message-channel-demo/index.html HEIGHT 666
# Assets
pages/playground
pages/i-directional-multimessage-message-channel-demo