libevent-extra-1.4-2 binary package in Ubuntu Xenial amd64

 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 /dev/poll,
 kqueue(2), event ports, select(2), poll(2) and epoll(4).
 .
 The libevent_extra library includes code for HTTP, DNS, RPC, and so
 on.
 .
 If you're writing software that uses libevent's protocol support, you
 need to link libevent_core and libevent_extra as well.

Source package