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.

libevent is meant to replace the asynchronous event loop found in
event driven network servers.  Currently, libevent supports kqueue(2),
select(2) and epoll(4).

1. build dependencies:
   1. libssl-devel
   2. zlib-devel