Websockets (error) handling larger incoming messages

Steps to Reproduce

run the attached example
click the buttons to test the server's / client engine's behavior when the appserver's message size limits are exceeded (red buttons)

Current Result

Tomcat:

• shows error box at client side
• no error in server logs
• retries falling back to /zkau produce error code 467
• after cancelling /zkau continues to work

Jetty:

• no error box at client side
• exception at server side 'MessageTooLargeException: Frame is too large'
• no attempt to retry
• fallback to /zkau continues to work

Expected Result

• consistent error handling where possible, client side and/or server side
• reliable retry mechanism using /zkau fallback

Ideally detect message size limits and chunk them or use a streaming method

Debug Info

Root Cause

application server specific websocket request size limits
tomcat: 8192 bytes docs
jetty: 65536 bytes source

Workaround

on tomcat increase size limit (the default size 8kb is quite limiting)
e.g. 64kb which is the default in Jetty makes accidental problem less likely to happen

		<context-param>
			<param-name>org.apache.tomcat.websocket.textBufferSize</param-name>
			<param-value>65536</param-value>
		</context-param>

see: https://tomcat.apache.org/tomcat-8.5-doc/web-socket-howto.html