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.

libevent is meant to replace the asynchronous event loop found in
event driven network servers. An application just needs to call
event_dispatch() and can then add or remove events dynamically
without having to change the event loop.

Currently, libevent supports /dev/poll, kqueue(2), event ports,
select(2), poll(2), and epoll(4). 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.

Libevent additionally provides a sophisticated framework for buffered
network IO, with support for sockets, filters, rate-limiting, SSL,
zero-copy file transmission, and IOCP. Libevent includes support
for several useful protocols, including DNS, HTTP, and a minimal
RPC framework.