<s>
libtorrent	B-Language
is	O
an	O
open-source	B-License
implementation	O
of	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
It	O
is	O
written	O
in	O
and	O
has	O
its	O
main	O
library	B-Library
interface	O
in	O
C++	B-Language
.	O
</s>
<s>
Its	O
most	O
notable	O
features	O
are	O
support	O
for	O
Mainline	B-Protocol
DHT	I-Protocol
,	O
IPv6	B-Protocol
,	O
HTTP	O
seeds	O
and	O
μTorrent	B-Application
's	O
peer	O
exchange	O
.	O
</s>
<s>
libtorrent	B-Language
uses	O
Boost	B-Language
,	O
specifically	O
Boost.Asio	B-Language
to	O
gain	O
its	O
platform	O
independence	O
.	O
</s>
<s>
It	O
is	O
known	O
to	O
build	O
on	O
Windows	B-Application
and	O
most	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
(	O
OS	B-Operating_System
X	I-Operating_System
,	O
Linux	B-Application
,	O
and	O
many	O
BSDs	B-Operating_System
)	O
.	O
</s>
<s>
libtorrent	B-Language
is	O
kept	O
up	O
to	O
date	O
with	O
bittorrent	B-Protocol
extensions	O
that	O
developers	O
deem	O
most	O
useful	O
,	O
and	O
is	O
actively	O
being	O
optimized	O
to	O
work	O
in	O
a	O
broader	O
set	O
of	O
environments	O
.	O
</s>
<s>
It	O
aims	O
to	O
be	O
the	O
most	O
suitable	O
libtorrent	B-Language
implementation	O
for	O
embedded	O
devices	O
as	O
well	O
as	O
desktops	O
and	O
seed-servers	O
.	O
</s>
<s>
The	O
original	O
author	O
of	O
libtorrent	B-Language
is	O
Arvid	O
Norberg	O
.	O
</s>
<s>
It	O
is	O
the	O
first	O
client	O
to	O
support	O
the	O
extension	O
protocol	O
together	O
with	O
μTorrent	B-Application
,	O
which	O
is	O
now	O
a	O
foundation	O
that	O
many	O
other	O
extensions	O
build	O
upon	O
.	O
</s>
<s>
BEPs	O
are	O
a	O
part	O
of	O
the	O
BitTorrent	B-Protocol
Enhancement	O
Proposal	O
Process	O
.	O
</s>
<s>
A	O
BEP	O
is	O
a	O
design	O
document	O
providing	O
information	O
to	O
the	O
BitTorrent	B-Protocol
community	O
,	O
or	O
describing	O
a	O
new	O
feature	O
for	O
the	O
BitTorrent	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
They	O
were	O
intended	O
to	O
be	O
the	O
primary	O
mechanisms	O
for	O
proposing	O
new	O
features	O
,	O
for	O
collecting	O
community	O
input	O
on	O
an	O
issue	O
,	O
and	O
for	O
documenting	O
the	O
design	O
decisions	O
that	O
have	O
gone	O
into	O
BitTorrent	B-Protocol
.	O
</s>
<s>
A	O
Standards	O
Track	O
BEP	O
describes	O
an	O
extension	O
to	O
one	O
of	O
the	O
BitTorrent	B-Protocol
protocols	I-Protocol
or	O
a	O
change	O
in	O
the	O
behavior	O
of	O
one	O
of	O
the	O
actors	O
in	O
these	O
protocols	O
,	O
where	O
the	O
actors	O
are	O
currently	O
clients	O
,	O
trackers	B-Protocol
,	O
and	O
web	O
servers	O
.	O
</s>
<s>
An	O
Informational	O
BEP	O
describes	O
a	O
BitTorrent	B-Protocol
design	O
issue	O
,	O
or	O
provides	O
general	O
guidelines	O
or	O
information	O
to	O
the	O
BitTorrent	B-Protocol
community	O
,	O
but	O
does	O
not	O
propose	O
an	O
extension	O
.	O
</s>
<s>
Informational	O
BEPs	O
do	O
not	O
necessarily	O
represent	O
a	O
BitTorrent	B-Protocol
community	O
consensus	O
or	O
recommendation	O
,	O
so	O
users	O
and	O
implementors	O
are	O
free	O
to	O
ignore	O
Informational	O
BEPs	O
or	O
follow	O
their	O
advice	O
.	O
</s>
<s>
A	O
Process	O
BEP	O
describes	O
a	O
process	O
surrounding	O
BitTorrent	B-Protocol
or	O
proposes	O
a	O
change	O
to	O
(	O
or	O
an	O
event	O
in	O
)	O
a	O
process	O
.	O
</s>
<s>
Process	O
BEPs	O
are	O
like	O
Standards	O
Track	O
BEPs	O
but	O
apply	O
to	O
areas	O
other	O
than	O
the	O
BitTorrent	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
Examples	O
include	O
release	O
schedules	O
,	O
procedures	O
,	O
guidelines	O
,	O
changes	O
to	O
the	O
decision-making	O
process	O
,	O
and	O
changes	O
to	O
the	O
tools	O
or	O
environment	O
used	O
in	O
BitTorrent	B-Protocol
development	O
.	O
</s>
<s>
supports	O
the	O
μTorrent	B-Application
peer	O
exchange	O
protocol	O
(	O
PEX	O
)	O
.	O
</s>
<s>
supports	O
the	O
no_peer_id	O
=	O
1	O
extension	O
that	O
will	O
ease	O
the	O
load	O
off	O
trackers	B-Protocol
.	O
</s>
<s>
supports	O
the	O
compact	O
=	O
1	O
tracker	B-Protocol
parameter	O
.	O
</s>
<s>
support	O
for	O
merkle	B-Algorithm
hash	I-Algorithm
tree	I-Algorithm
torrents	B-Protocol
.	O
</s>
<s>
This	O
makes	O
the	O
size	O
of	O
torrent	B-Protocol
files	O
scale	O
well	O
with	O
the	O
size	O
of	O
the	O
content	O
.	O
</s>
<s>
fast	O
resume	O
support	O
,	O
a	O
way	O
to	O
get	O
rid	O
of	O
the	O
costly	O
piece	O
check	O
at	O
the	O
start	O
of	O
a	O
resumed	O
torrent	B-Protocol
.	O
</s>
<s>
queues	O
torrents	B-Protocol
for	O
file	O
check	O
,	O
instead	O
of	O
checking	O
all	O
of	O
them	O
in	O
parallel	O
.	O
</s>
<s>
does	O
not	O
have	O
any	O
requirements	O
on	O
the	O
piece	O
order	O
in	O
a	O
torrent	B-Protocol
that	O
it	O
resumes	O
.	O
</s>
<s>
This	O
means	O
it	O
can	O
resume	O
a	O
torrent	B-Protocol
downloaded	O
by	O
any	O
client	O
.	O
</s>
<s>
The	O
ability	O
to	O
select	O
which	O
parts	O
of	O
a	O
torrent	B-Protocol
you	O
want	O
to	O
download	O
.	O
</s>
<s>
can	O
proxy	O
torrent	B-Protocol
traffic	O
through	O
the	O
I2P	B-Protocol
anonymity	O
network	O
.	O
</s>
<s>
All	O
disk	O
I/O	O
in	O
libtorrent	B-Language
is	O
done	O
asynchronously	O
to	O
the	O
network	O
thread	O
,	O
by	O
the	O
disk	O
io	O
thread	O
.	O
</s>
<s>
In	O
order	O
to	O
conserve	O
memory	O
,	O
and	O
system	O
calls	O
,	O
iovec	B-General_Concept
file	I-General_Concept
operations	I-General_Concept
are	O
used	O
to	O
flush	O
multiple	O
cache	O
blocks	O
in	O
a	O
single	O
call	O
.	O
</s>
<s>
The	O
send	O
buffer	O
is	O
then	O
encrypted	O
with	O
the	O
peer	O
specific	O
key	O
and	O
chained	O
onto	O
the	O
iovec	B-General_Concept
for	O
sending	O
.	O
</s>
<s>
The	O
piece	O
picker	O
is	O
a	O
central	O
component	O
in	O
a	O
bittorrent	B-Protocol
implementation	O
.	O
</s>
<s>
The	O
piece	O
picker	O
in	O
libtorrent	B-Language
is	O
optimized	O
for	O
quickly	O
finding	O
the	O
rarest	O
pieces	O
.	O
</s>
<s>
This	O
is	O
BEP30	O
of	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Merkle	B-Algorithm
hash	I-Algorithm
tree	I-Algorithm
torrents	B-Protocol
is	O
an	O
extension	O
that	O
lets	O
a	O
torrent	B-Protocol
file	O
only	O
contain	O
the	O
root	O
hash	O
of	O
the	O
hash	O
tree	O
forming	O
the	O
piece	O
hashes	O
.	O
</s>
<s>
The	O
main	O
benefit	O
of	O
this	O
feature	O
is	O
that	O
regardless	O
of	O
how	O
many	O
pieces	O
there	O
are	O
in	O
a	O
torrent	B-Protocol
,	O
the	O
.torrent	O
file	O
will	O
always	O
be	O
the	O
same	O
size	O
.	O
</s>
<s>
With	O
regular	O
torrents	B-Protocol
,	O
clients	O
have	O
to	O
request	O
multiple	O
blocks	O
for	O
pieces	O
,	O
typically	O
from	O
different	O
peers	O
,	O
before	O
the	O
data	O
can	O
be	O
verified	O
against	O
the	O
piece	O
hash	O
.	O
</s>
<s>
The	O
piece	O
size	O
in	O
regular	O
torrents	B-Protocol
is	O
a	O
tradeoff	O
between	O
the	O
size	O
of	O
the	O
.torrent	O
file	O
itself	O
and	O
the	O
piece	O
size	O
.	O
</s>
<s>
Often	O
,	O
for	O
files	O
that	O
are	O
4	O
GB	O
,	O
the	O
piece	O
size	O
is	O
2	O
or	O
4	O
MB	O
,	O
just	O
to	O
avoid	O
making	O
the	O
.torrent	O
file	O
too	O
big	O
.	O
</s>
<s>
Merkle	O
torrents	B-Protocol
solves	O
these	O
problems	O
by	O
removing	O
the	O
tradeoff	O
between	O
.torrent	O
size	O
and	O
piece	O
size	O
.	O
</s>
<s>
With	O
merkle	O
torrents	B-Protocol
,	O
the	O
piece	O
size	O
can	O
be	O
the	O
minimum	O
block	O
size	O
(	O
16	O
KB	O
)	O
,	O
which	O
lets	O
peers	O
verify	O
every	O
block	O
of	O
data	O
received	O
from	O
peers	O
,	O
immediately	O
.	O
</s>
<s>
Some	O
applications	O
that	O
use	O
libtorrent	B-Language
:	O
</s>
<s>
Runes	B-Protocol
of	I-Protocol
Magic	I-Protocol
,	O
an	O
MMORPG	O
whose	O
FOG	O
downloader	O
uses	O
libtorrent	B-Language
for	O
updating	O
the	O
game	O
client	O
.	O
</s>
<s>
World	B-Application
of	I-Application
Tanks	I-Application
,	O
a	O
MMORPG	O
whose	O
launcher	O
uses	O
libtorrent	B-Language
for	O
updating	O
the	O
game	O
client	O
.	O
</s>
