<s>
libevent	B-Language
is	O
a	O
software	B-Library
library	I-Library
that	O
provides	O
asynchronous	O
event	O
notification	O
.	O
</s>
<s>
The	O
libevent	B-Language
API	B-General_Concept
provides	O
a	O
mechanism	O
to	O
execute	O
a	O
callback	O
function	O
when	O
a	O
specific	O
event	O
occurs	O
on	O
a	O
file	B-Application
descriptor	I-Application
or	O
after	O
a	O
timeout	O
has	O
been	O
reached	O
.	O
</s>
<s>
libevent	B-Language
also	O
supports	O
callbacks	O
triggered	O
by	O
signals	B-Operating_System
and	O
regular	O
timeouts	O
.	O
</s>
<s>
libevent	B-Language
is	O
meant	O
to	O
replace	O
the	O
event	B-General_Concept
loop	I-General_Concept
found	O
in	O
event-driven	O
network	B-Application
servers	I-Application
.	O
</s>
<s>
An	O
application	O
can	O
just	O
call	O
event_dispatch( )	O
and	O
then	O
add	O
or	O
remove	O
events	O
dynamically	O
without	O
having	O
to	O
change	O
the	O
event	B-General_Concept
loop	I-General_Concept
.	O
</s>
<s>
Currently	O
,	O
libevent	B-Language
supports	O
/dev/poll	O
,	O
kqueue(2 )	O
,	O
POSIX	O
select(2 )	O
,	O
Windows	O
IOCP	B-Library
,	O
poll(2 )	O
,	O
epoll(7 )	O
and	O
Solaris	B-Application
event	O
ports	O
.	O
</s>
<s>
It	O
also	O
has	O
experimental	O
support	O
for	O
real-time	O
signals	B-Operating_System
.	O
</s>
<s>
The	O
exposed	O
event	O
API	B-General_Concept
is	O
uniform	O
over	O
all	O
of	O
the	O
supported	O
platforms	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
libevent	B-Language
allows	O
for	O
portable	B-Architecture
application	O
development	O
and	O
provides	O
"	O
the	O
most	O
scalable	B-Architecture
event	O
notification	O
mechanism	O
available	O
on	O
an	O
operating	O
system	O
"	O
.	O
</s>
<s>
Using	O
callbacks	O
on	O
signals	B-Operating_System
,	O
libevent	B-Language
makes	O
it	O
possible	O
to	O
write	O
"	O
secure	O
"	O
signal	B-Operating_System
handlers	I-Operating_System
as	O
none	O
of	O
the	O
user	O
supplied	O
signal	B-Operating_System
handling	I-Operating_System
code	O
runs	O
in	O
the	O
signal	O
's	O
context	B-Operating_System
.	O
</s>
<s>
libevent	B-Language
was	O
created	O
by	O
Niels	O
Provos	O
and	O
is	O
maintained	O
primarily	O
by	O
Azat	O
Khuzhin	O
.	O
</s>
<s>
It	O
is	O
released	O
under	O
a	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Some	O
of	O
the	O
notable	O
applications	O
that	O
take	O
advantage	O
of	O
libevent	B-Language
are	O
:	O
</s>
<s>
libevent	B-Language
2.1	O
was	O
released	O
on	O
April	O
3	O
,	O
2012	O
.	O
</s>
<s>
libevent	B-Language
2.0	O
was	O
released	O
on	O
April	O
17	O
,	O
2009	O
.	O
</s>
<s>
libevent	B-Language
1.4	O
was	O
released	O
on	O
November	O
11	O
,	O
2007	O
.	O
</s>
<s>
libevent	B-Language
1.3	O
was	O
released	O
on	O
February	O
15	O
,	O
2007	O
.	O
</s>
<s>
libevent	B-Language
1.2	O
was	O
released	O
on	O
October	O
15	O
,	O
2006	O
.	O
</s>
<s>
libevent	B-Language
1.1	O
was	O
released	O
on	O
May	O
14	O
,	O
2005	O
.	O
</s>
