Broker websocket client connections not closed correctly

[simeonmiteff]

It looks like the CAF websocket implementation can do websocket close frames but I have never seen broker/zeek use it to close a connection to a client correctly - it just drops the TCP connection (whether that is due to something weird like #458 or just because zeek is terminating). It would be useful to correct this.

[Neverlord]

If this happens during shutdown, it might be that Broker just won't give the managed sockets any time for sending shutdown messages. I'll see what I can do.