That is very odd. As far as I can tell, this event should not trigger for UDP sockets. The on SOCKWRITE event is used with TCP sockets to let you know when you can send more data or to let you know if there is an error. However, UDP events are inherently unreliable and there is no guarantee that you will receive any errors at all if a packet does not reach its destination.
If the on sockwrite should not trigger for UDP sockets, how does one prevents filling up the queue? or send more data once the queue is filled. (and prevent getting things like "* /sockudp: 'test' queue would exceed 16384 bytes").
Even though UDP is unreliable (although it mostly is successful), the $sockerr on sockwrite should surely relay the possible errors returned by winsock, is that not the case?