Binary vs text websocket frames

[Christian Schafmeister]

Hello,

How can I control whether the jupyter server sends binary websocket frames vs text websocket frames to the browser?

When monitoring websocket traffic between an ipython jupyter notebook kernel and the browser, all websocket frames, both to the browser and from the browser are in websocket text frames.  This makes it easy to read the JSON dictionaries using almost any browser.

When monitoring websocket traffic between our Common Lisp kernel and a browser, the websocket frames to the browser are binary websocket frames and the frames from the browser are websocket text frames. 

I recently learned that it is the jupyter notebook server (written in python) that is interposed between our kernel and the browser that is carrying out this websocket communication.  Why is it using binary frames?  Binary websocket frames are a lot harder to dig into and extract the JSON from.

I'd like to monitor the websocket traffic between the jupyter server and the browser for debugging.

It has been extremely helpful to do this in a painful/limited way to add jupyter widgets support to our kernel (based on cl-jupyter/Common Lisp).

Best,

Christian Schafmeister

Professor

Chemistry Department

Temple University

[Jason Grout]

The websocket frames are sent in either binary or text, depending on whether there are binary buffers encoded in the message (it is a per-message decision, not an overall decision). The decision logic is here: https://github.com/jupyter/notebook/blob/ca50f1af5afb525fd95b98b2e61e69db28094467/notebook/base/zmqhandlers.py#L230

I think it would be very useful to have either something that can log the messages in the kernel, right around that logic. Another interesting change would be to have a debug switch in the notebook server that encodes any binary message buffers with base64 so the websocket message can still be a text websocket frame. Another place to put the logging logic is in the frontend, after the message has been converted back into a native js object.

Jason

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[Christian Schafmeister]

Thank you very much!

Our messages appear to always add a "buffers" field even when the list of buffers is empty.  I'll fix that.