No support for events or explanation why they are not supported

[endobson]

I want to synchronize on a message being received from the client or something else happening (e.g. server producing data). I want to use events but it seems that websockets don't support that. If there is a good reason why they cannot be supported safely/efficiently then I would expect that to be documented.

[endobson]

It actually looks like there is some support by looking at the examples, but without documentation I have no idea what the guarantees are nor the API.
https://github.com/tonyg/racket-rfc6455/blob/master/net/rfc6455/examples/test-server.rkt