Event::READ
This flag indicates an event that becomes active when the provided file
descriptor (usually a stream resource, or socket) is ready for reading.
Event::WRITE
flag indicates an event that becomes active when the provided file
descriptor (usually a stream resource, or socket) is ready for writing.
Event::SIGNAL
used to implement signal detection. See "Constructing signal events" below.
Event::TIMEOUT
indicates an event that becomes active after a timeout elapses. The
Event::TIMEOUT
flag is ignored when constructing an event: one can either set a timeout
when event is
added
, or not. It is set in the
$what
argument to the callback function when a timeout has occurred.
See also ? Fast portable non-blocking network programming with Libevent, Working with events, Event flags