The libevent 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 event loop found in event driven network servers. An application just needs to call event_dispatch() and then add or remove events dynamically without having to change the event loop.
Programs using libevent
The usefulness of libevent API is demonstrated by the following applications:
- Vomit – Voice Over Misconfigured Internet Telephones
- Crawl – A Small and Efficient HTTP Crawler
- Libio – an input/output abstraction library
- Honeyd – a virtual honeynet daemon – can be used to fight Internet worms.
- Fragroute – an IDS testing tool
- Nylon – nested proxy server
- Disconcert – a Distributed Computing Framework for Loosely-Coupled Workstations.
- PLB – pure load balancer: a free high-performance load balancer for Unix.
- Trickle – a lightweight userspace bandwidth shaper.
- Memcached – a high-performance, distributed memory object caching system.
- watchcatd – software watchdog designed to take actions not as drastic as the usual solutions, which reset the machine.
- ScanSSH – a fast SSH server and open proxy scanner.
- Nttlscan – a network topology scanner for Honeyd.
- NetChat – a combination of netcat and ppp’s chat.
- Io – a small programming language; uses libevent for network communication.
- Tor – an anonymous Internet communication system.
- Systrace – a system call sandbox.
- SpyBye – detect malware on web pages.
- GreenSQL – an SQL database firewall.
- dnsscan – a fast scanner for identifying open recursive dns resolvers
- Kargo Event – a PHP extension for libevent.