Since v3.3t 2014.11.26
websocket port close -- called AFTER a websocket connection has been closed
as the connection has been closed by the time .z.wc is called there are strictly no remote values that can be put into .z.a, .z.u or .z.w so the local values are returned.
to allow you to cleanup things like tables of users keyed by handle the handle that WAS being used is passed as a parameter to .z.wc
For a complete list of functions, see the kdb+ Function Reference.