Transport

The Transport base class is intended to abstract a number of client-host communication mechanisms.

The basic pattern is that the application registers callbacks to listen for connections, messages and disconnections. Note that the application should not assume that there is only a single connection. There can be multiple remote connections at one time (i.e. multiple cells in a Jupyter Notebook, or multiple UIWebWidgets in an iOS app), which can be tracked by listening to the onInitialize and onFinalize events.

Some examples of communication mechanisms that could be managed via the Transport API:

• Jupyter Widget based communication between a browser and a notebook
• Browser: postMessage based communication between tabs and iframes
• Android: Communication between Java application and JavaScript running in a WebView component
• iOS: Communication between Swift and JavaScript running in a UIWebView component

Usage

Listening to transport connections, disconnections and messages

Transport.setCallbacks({
  onInitialize: (message) => console.log('A new transport connected'),
  onFinalize: (message) => console.log('A transport disconnected'),
  onMessage: (message) => console.log('A message arrived on a connection')
});

Static Members

Transport.setCallbacks(callbacks: object): void

The following callbacks can be set:

• callbacks.onInitialize
• callbacks.onMessage
• callbacks.onFinalize

Methods

constructor

Note: The Transport class should not be instantiated explicitly by JavaScript applications. Transport instances are automatically created.

Remarks

Longer term goals:

• WebSocket based transport
• Possibly add additional transports such as Colab notebook specific APIs.
• Binary data
• Back-channel: Events
• Back-channel: Errors