# Event flags

`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