[ excerpt from developer's www site ]

An ocaml wrapper for the libevent API. The libevent API provides a
mechanism to execute a callback function when a specific event
occurs on a file descriptor or after a timeout has been reached.
Furthermore, libevent also support callbacks due to signals or
regular timeouts.

Currently, libevent supports /dev/poll, kqueue(2), select(2), poll(2)
and epoll(4). It also has experimental support for real-time signals.
The internal event mechanism is completely independent of the exposed
event API, and a simple update of libevent can provide new functionality
without having to redesign the applications. As a result, Libevent
allows for portable application development and provides the most
scalable event notification mechanism available on an operating
system.

WWW: http://www.xs4all.nl/~mmzeeman/ocaml/