<s>
is	O
a	O
message-oriented	B-Application
middleware	I-Application
mechanism	O
that	O
allows	O
communication	O
between	O
multiple	O
processes	B-Operating_System
running	O
concurrently	O
on	O
the	O
same	O
machine	O
.	O
</s>
<s>
D-Bus	B-Language
was	O
developed	O
as	O
part	O
of	O
the	O
freedesktop.org	B-Application
project	O
,	O
initiated	O
by	O
Havoc	O
Pennington	O
from	O
Red	O
Hat	O
to	O
standardize	O
services	O
provided	O
by	O
Linux	B-Operating_System
desktop	O
environments	O
such	O
as	O
GNOME	B-Application
and	O
KDE	B-Application
.	O
</s>
<s>
The	O
freedesktop.org	B-Application
project	O
also	O
developed	O
a	O
free	B-License
and	I-License
open-source	I-License
software	I-License
library	B-Library
called	O
libdbus	O
,	O
as	O
a	O
reference	O
implementation	O
of	O
the	O
specification	O
.	O
</s>
<s>
This	O
library	B-Library
should	O
not	O
be	O
confused	O
with	O
D-Bus	B-Language
itself	O
,	O
as	O
other	O
implementations	O
of	O
the	O
D-Bus	B-Language
specification	O
also	O
exist	O
,	O
such	O
as	O
GDBus	O
(	O
GNOME	B-Application
)	O
,	O
QtDBus	O
(	O
Qt/KDE	O
)	O
,	O
dbus-java	O
and	O
sd-bus	O
(	O
part	O
of	O
systemd	B-Application
)	O
.	O
</s>
<s>
D-Bus	B-Language
is	O
an	O
inter-process	B-Operating_System
communication	I-Operating_System
(	O
IPC	O
)	O
mechanism	O
initially	O
designed	O
to	O
replace	O
the	O
software	O
component	O
communications	O
systems	O
used	O
by	O
the	O
GNOME	B-Application
and	O
KDE	B-Application
Linux	B-Operating_System
desktop	O
environments	O
(	O
CORBA	B-Architecture
and	O
DCOP	B-Language
respectively	O
)	O
.	O
</s>
<s>
The	O
components	O
of	O
these	O
desktop	O
environments	O
are	O
normally	O
distributed	O
in	O
many	O
processes	B-Operating_System
,	O
each	O
one	O
providing	O
only	O
a	O
few	O
—	O
usually	O
one	O
—	O
services	O
.	O
</s>
<s>
These	O
services	O
may	O
be	O
used	O
by	O
regular	O
client	O
applications	B-Application
or	O
by	O
other	O
components	O
of	O
the	O
desktop	O
environment	O
to	O
perform	O
their	O
tasks	O
.	O
</s>
<s>
Due	O
to	O
the	O
large	O
number	O
of	O
processes	B-Operating_System
involved	O
—	O
adding	O
up	O
processes	B-Operating_System
providing	O
the	O
services	O
and	O
clients	O
accessing	O
them	O
—	O
establishing	O
one-to-one	O
IPC	O
between	O
all	O
of	O
them	O
becomes	O
an	O
inefficient	O
and	O
quite	O
unreliable	O
approach	O
.	O
</s>
<s>
Instead	O
,	O
D-Bus	B-Language
provides	O
a	O
software-bus	B-Architecture
abstraction	B-Application
that	O
gathers	O
all	O
the	O
communications	O
between	O
a	O
group	O
of	O
processes	B-Operating_System
over	O
a	O
single	O
shared	O
virtual	O
channel	O
.	O
</s>
<s>
Processes	B-Operating_System
connected	O
to	O
a	O
bus	O
do	O
not	O
know	O
how	O
it	O
is	O
internally	O
implemented	O
,	O
but	O
D-Bus	B-Language
specification	O
guarantees	O
that	O
all	O
processes	B-Operating_System
connected	O
to	O
the	O
bus	O
can	O
communicate	O
with	O
each	O
other	O
through	O
it	O
.	O
</s>
<s>
Linux	B-Operating_System
desktop	O
environments	O
take	O
advantage	O
of	O
the	O
D-Bus	B-Language
facilities	O
by	O
instantiating	O
multiple	O
buses	O
,	O
notably	O
:	O
</s>
<s>
a	O
single	O
system	O
bus	O
,	O
available	O
to	O
all	O
users	O
and	O
processes	B-Operating_System
of	O
the	O
system	O
,	O
that	O
provides	O
access	O
to	O
system	O
services	O
(	O
i.e.	O
</s>
<s>
D-Bus	B-Language
provides	O
additional	O
or	O
simplifies	O
existing	O
functionality	O
to	O
the	O
applications	B-Application
,	O
including	O
information-sharing	O
,	O
modularity	O
and	O
privilege	O
separation	O
.	O
</s>
<s>
For	O
example	O
,	O
information	O
on	O
an	O
incoming	O
voice-call	O
received	O
through	O
Bluetooth	B-Protocol
or	O
Skype	B-Application
can	O
be	O
propagated	O
and	O
interpreted	O
by	O
any	O
currently-running	O
music	O
player	O
,	O
which	O
can	O
react	O
by	O
muting	O
the	O
volume	O
or	O
by	O
pausing	O
playback	O
until	O
the	O
call	O
is	O
finished	O
.	O
</s>
<s>
D-Bus	B-Language
can	O
also	O
be	O
used	O
as	O
a	O
framework	B-Architecture
to	O
integrate	O
different	O
components	O
of	O
a	O
user	O
application	O
.	O
</s>
<s>
For	O
instance	O
,	O
an	O
office	O
suite	O
can	O
communicate	O
through	O
the	O
session	O
bus	O
to	O
share	O
data	O
between	O
a	O
word	B-General_Concept
processor	I-General_Concept
and	O
a	O
spreadsheet	B-Application
.	O
</s>
<s>
Every	O
connection	O
to	O
a	O
bus	O
is	O
identified	O
in	O
the	O
context	O
of	O
D-Bus	B-Language
by	O
what	O
is	O
called	O
a	O
bus	O
name	O
.	O
</s>
<s>
In	O
D-Bus	B-Language
parlance	O
,	O
when	O
a	O
bus	O
name	O
is	O
assigned	O
to	O
a	O
connection	O
,	O
it	O
is	O
said	O
the	O
connection	O
owns	O
the	O
bus	O
name	O
.	O
</s>
<s>
Bus	O
names	O
can	O
be	O
used	O
as	O
a	O
simple	O
way	O
to	O
implement	O
single-instance	O
applications	B-Application
(	O
second	O
instances	O
detect	O
that	O
the	O
bus	O
name	O
is	O
already	O
taken	O
)	O
.	O
</s>
<s>
Because	O
of	O
its	O
original	O
conception	O
as	O
a	O
replacement	O
for	O
several	O
component	O
oriented	O
communications	O
systems	O
,	O
D-Bus	B-Language
shares	O
with	O
its	O
predecessors	O
an	O
object	O
model	O
in	O
which	O
to	O
express	O
the	O
semantics	O
of	O
the	O
communications	O
between	O
clients	O
and	O
services	O
.	O
</s>
<s>
The	O
terms	O
used	O
in	O
the	O
D-Bus	B-Language
object	O
model	O
mimic	O
those	O
used	O
by	O
some	O
object	B-Language
oriented	I-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
That	O
does	O
not	O
mean	O
that	O
D-Bus	B-Language
is	O
somehow	O
limited	O
to	O
OOP	O
languages	O
—	O
in	O
fact	O
,	O
the	O
most	O
used	O
implementation	O
(	O
)	O
is	O
written	O
in	O
C	B-Language
,	O
a	O
procedural	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
In	O
D-Bus	B-Language
,	O
a	O
process	O
offers	O
its	O
services	O
by	O
exposing	O
objects	O
.	O
</s>
<s>
Clients	O
should	O
instruct	O
the	O
bus	O
that	O
they	O
are	O
interested	O
in	O
receiving	O
certain	O
signals	O
from	O
a	O
particular	O
object	O
,	O
since	O
a	O
D-Bus	B-Language
bus	O
only	O
passes	O
signals	O
to	O
those	O
processes	B-Operating_System
with	O
a	O
registered	O
interest	O
in	O
them	O
.	O
</s>
<s>
A	O
process	O
connected	O
to	O
a	O
D-Bus	B-Language
bus	O
can	O
request	O
it	O
to	O
export	O
as	O
many	O
D-Bus	B-Language
objects	O
as	O
it	O
wants	O
.	O
</s>
<s>
Each	O
object	O
is	O
identified	O
by	O
an	O
object	O
path	O
,	O
a	O
string	O
of	O
numbers	O
,	O
letters	O
and	O
underscores	O
separated	O
and	O
prefixed	O
by	O
the	O
slash	O
character	O
,	O
called	O
that	O
because	O
of	O
their	O
resemblance	O
to	O
Unix	O
filesystem	B-Application
paths	O
.	O
</s>
<s>
Every	O
object	O
is	O
inextricably	O
associated	O
to	O
the	O
particular	O
bus	O
connection	O
where	O
it	O
was	O
exported	O
,	O
and	O
,	O
from	O
the	O
D-Bus	B-Language
point	O
of	O
view	O
,	O
only	O
lives	O
in	O
the	O
context	O
of	O
such	O
connection	O
.	O
</s>
<s>
This	O
in	O
turn	O
allows	O
that	O
several	O
processes	B-Operating_System
connected	O
to	O
the	O
bus	O
can	O
export	O
different	O
objects	O
with	O
identical	O
object	O
paths	O
unambiguously	O
.	O
</s>
<s>
It	O
is	O
a	O
set	O
of	O
declarations	O
of	O
methods	O
(	O
including	O
its	O
passing	O
and	O
returning	O
parameters	O
)	O
and	O
signals	O
(	O
including	O
its	O
parameters	O
)	O
identified	O
by	O
a	O
dot-separated	O
name	O
resembling	O
the	O
Java	B-Language
language	I-Language
interfaces	O
notation	O
.	O
</s>
<s>
A	O
D-Bus	B-Language
object	O
can	O
implement	O
several	O
interfaces	O
,	O
but	O
at	O
least	O
must	O
implement	O
one	O
,	O
providing	O
support	O
for	O
every	O
method	O
and	O
signal	O
defined	O
by	O
it	O
.	O
</s>
<s>
The	O
D-Bus	B-Language
specification	O
also	O
defines	O
several	O
standard	O
interfaces	O
that	O
objects	O
may	O
want	O
to	O
implement	O
in	O
addition	O
to	O
its	O
own	O
interfaces	O
.	O
</s>
<s>
Although	O
technically	O
optional	O
,	O
most	O
D-Bus	B-Language
service	O
developers	O
choose	O
to	O
support	O
them	O
in	O
their	O
exported	O
objects	O
since	O
they	O
offer	O
important	O
additional	O
features	O
to	O
D-Bus	B-Language
clients	O
,	O
such	O
as	O
introspection	B-Application
.	O
</s>
<s>
:	O
provides	O
a	O
way	O
to	O
test	O
if	O
a	O
D-Bus	B-Language
connection	O
is	O
alive	O
.	O
</s>
<s>
:	O
provides	O
an	O
introspection	B-Application
mechanism	O
by	O
which	O
a	O
client	O
process	O
can	O
,	O
at	O
run-time	O
,	O
get	O
a	O
description	O
(	O
in	O
XML	B-Protocol
format	O
)	O
of	O
the	O
interfaces	O
,	O
methods	O
and	O
signals	O
that	O
the	O
object	O
implements	O
.	O
</s>
<s>
:	O
allows	O
a	O
D-Bus	B-Language
object	O
to	O
expose	O
the	O
underlying	O
native	O
object	O
properties	B-Language
or	O
attributes	O
,	O
or	O
simulate	O
them	O
if	O
it	O
does	O
not	O
exist	O
.	O
</s>
<s>
:	O
when	O
a	O
D-Bus	B-Language
service	O
arranges	O
its	O
objects	O
hierarchically	O
,	O
this	O
interface	O
provides	O
a	O
way	O
to	O
query	O
an	O
object	O
about	O
all	O
sub-objects	O
under	O
its	O
path	O
,	O
as	O
well	O
as	O
their	O
interfaces	O
and	O
properties	B-Language
,	O
using	O
a	O
single	O
method	O
call	O
.	O
</s>
<s>
The	O
D-Bus	B-Language
specification	O
defines	O
a	O
number	O
of	O
administrative	O
bus	O
operations	O
(	O
called	O
"	O
bus	O
services	O
"	O
)	O
to	O
be	O
performed	O
using	O
the	O
object	O
that	O
resides	O
in	O
the	O
bus	O
name	O
.	O
</s>
<s>
D-Bus	B-Language
was	O
conceived	O
as	O
a	O
generic	O
,	O
high-level	O
inter-process	B-Operating_System
communication	I-Operating_System
system	O
.	O
</s>
<s>
To	O
accomplish	O
such	O
goals	O
,	O
D-Bus	B-Language
communications	O
are	O
based	O
on	O
the	O
exchange	O
of	O
messages	O
between	O
processes	B-Operating_System
instead	O
of	O
"	O
raw	O
bytes	O
"	O
.	O
</s>
<s>
D-Bus	B-Language
messages	O
are	O
high-level	O
discrete	O
items	O
that	O
a	O
process	O
can	O
send	O
through	O
the	O
bus	O
to	O
another	O
connected	O
process	O
.	O
</s>
<s>
In	O
this	O
regard	O
,	O
D-Bus	B-Language
is	O
closer	O
to	O
an	O
RPC	B-Operating_System
mechanism	O
than	O
to	O
a	O
classic	O
IPC	O
mechanism	O
,	O
with	O
its	O
own	O
type	O
definition	O
system	O
and	O
its	O
own	O
marshaling	B-Application
.	O
</s>
<s>
One-to-one	O
request-response	B-Protocol
:	O
This	O
is	O
the	O
way	O
for	O
a	O
client	O
to	O
invoke	O
an	O
object	O
's	O
method	O
.	O
</s>
<s>
Publish/subscribe	B-Operating_System
:	O
This	O
is	O
the	O
way	O
for	O
an	O
object	O
to	O
announce	O
the	O
occurrence	O
of	O
a	O
signal	O
to	O
the	O
interested	O
parties	O
.	O
</s>
<s>
Every	O
D-Bus	B-Language
message	O
consists	O
of	O
a	O
header	O
and	O
a	O
body	O
.	O
</s>
<s>
All	O
the	O
data	O
is	O
encoded	O
in	O
a	O
well	O
known	O
binary	O
format	O
called	O
the	O
wire	O
format	O
which	O
supports	O
the	O
serialization	B-Application
of	O
various	O
types	O
,	O
such	O
as	O
integers	O
and	O
floating-point	O
numbers	O
,	O
strings	O
,	O
compound	O
types	O
,	O
and	O
so	O
on	O
,	O
also	O
referred	O
to	O
as	O
marshaling	B-Application
.	O
</s>
<s>
The	O
D-Bus	B-Language
specification	O
defines	O
the	O
wire	B-Protocol
protocol	I-Protocol
:	O
how	O
to	O
build	O
the	O
D-Bus	B-Language
messages	O
to	O
be	O
exchanged	O
between	O
processes	B-Operating_System
within	O
a	O
D-Bus	B-Language
connection	O
.	O
</s>
<s>
Most	O
existing	O
D-Bus	B-Language
implementations	O
follow	O
the	O
architecture	O
of	O
the	O
reference	O
implementation	O
.	O
</s>
<s>
a	O
point-to-point	O
communications	O
library	B-Library
that	O
implements	O
the	O
D-Bus	B-Language
wire	B-Protocol
protocol	I-Protocol
in	O
order	O
to	O
exchange	O
messages	O
between	O
two	O
processes	B-Operating_System
.	O
</s>
<s>
In	O
the	O
reference	O
implementation	O
this	O
library	B-Library
is	O
.	O
</s>
<s>
In	O
other	O
implementations	O
may	O
be	O
wrapped	O
by	O
another	O
higher-level	O
library	B-Library
,	O
language	B-Application
binding	I-Application
,	O
or	O
entirely	O
replaced	O
by	O
a	O
different	O
standalone	O
implementation	O
that	O
serves	O
the	O
same	O
purpose	O
.	O
</s>
<s>
This	O
library	B-Library
only	O
supports	O
one-to-one	O
communications	O
between	O
two	O
processes	B-Operating_System
.	O
</s>
<s>
a	O
special	O
daemon	B-Operating_System
process	I-Operating_System
that	O
plays	O
the	O
bus	O
role	O
and	O
to	O
which	O
the	O
rest	O
of	O
the	O
processes	B-Operating_System
connect	O
using	O
any	O
D-Bus	B-Language
point-to-point	O
communications	O
library	B-Library
.	O
</s>
<s>
This	O
process	O
is	O
also	O
known	O
as	O
the	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
,	O
since	O
it	O
is	O
responsible	O
for	O
routing	O
messages	O
from	O
any	O
process	O
connected	O
to	O
the	O
bus	O
to	O
another	O
.	O
</s>
<s>
Another	O
implementation	O
of	O
the	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
is	O
,	O
which	O
is	O
built	O
on	O
top	O
of	O
.	O
</s>
<s>
The	O
library	B-Library
(	O
or	O
its	O
equivalent	O
)	O
internally	O
uses	O
a	O
native	O
lower-level	O
IPC	O
mechanism	O
to	O
transport	O
the	O
required	O
D-Bus	B-Language
messages	O
between	O
the	O
two	O
processes	B-Operating_System
in	O
both	O
ends	O
of	O
the	O
D-Bus	B-Language
connection	O
.	O
</s>
<s>
D-Bus	B-Language
specification	O
does	O
not	O
mandate	O
which	O
particular	O
IPC	O
transport	O
mechanisms	O
should	O
be	O
available	O
to	O
use	O
,	O
as	O
it	O
is	O
the	O
communications	O
library	B-Library
that	O
decides	O
what	O
transport	O
methods	O
it	O
supports	O
.	O
</s>
<s>
For	O
instance	O
,	O
in	O
Unix-like	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
Linux	B-Operating_System
typically	O
uses	O
Unix	B-Protocol
domain	I-Protocol
sockets	I-Protocol
as	O
the	O
underlying	O
transport	O
method	O
,	O
but	O
it	O
also	O
supports	O
TCP	B-Protocol
sockets	I-Protocol
.	O
</s>
<s>
The	O
communications	O
libraries	O
of	O
both	O
processes	B-Operating_System
must	O
agree	O
on	O
the	O
selected	O
transport	O
method	O
and	O
also	O
on	O
the	O
particular	O
channel	O
used	O
for	O
their	O
communication	O
.	O
</s>
<s>
This	O
information	O
is	O
defined	O
by	O
what	O
D-Bus	B-Language
calls	O
an	O
address	O
.	O
</s>
<s>
Unix-domain	O
sockets	O
are	O
filesystem	B-Application
objects	O
,	O
and	O
therefore	O
they	O
can	O
be	O
identified	O
by	O
a	O
filename	O
,	O
so	O
a	O
valid	O
address	O
would	O
be	O
unix:path	O
=	O
/tmp/.hiddensocket	O
.	O
</s>
<s>
Both	O
processes	B-Operating_System
must	O
pass	O
the	O
same	O
address	O
to	O
their	O
respective	O
communications	O
libraries	O
to	O
establish	O
the	O
D-Bus	B-Language
connection	O
between	O
them	O
.	O
</s>
<s>
An	O
address	O
can	O
also	O
provide	O
additional	O
data	O
to	O
the	O
communications	O
library	B-Library
in	O
the	O
form	O
of	O
comma-separated	O
key	O
=	O
value	O
pairs	O
.	O
</s>
<s>
When	O
a	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
like	O
is	O
used	O
to	O
implement	O
a	O
D-Bus	B-Language
bus	O
,	O
all	O
processes	B-Operating_System
that	O
want	O
to	O
connect	O
to	O
the	O
bus	O
must	O
know	O
the	O
bus	O
address	O
,	O
the	O
address	O
by	O
which	O
a	O
process	O
can	O
establish	O
a	O
D-Bus	B-Language
connection	O
to	O
the	O
central	O
message	B-Application
bus	I-Application
process	O
.	O
</s>
<s>
In	O
this	O
scenario	O
,	O
the	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
selects	O
the	O
bus	O
address	O
and	O
the	O
remainder	O
processes	B-Operating_System
must	O
pass	O
that	O
value	O
to	O
their	O
corresponding	O
or	O
equivalent	O
libraries	O
.	O
</s>
<s>
These	O
addresses	O
are	O
defined	O
in	O
the	O
daemon	B-Operating_System
's	O
configuration	O
files	O
.	O
</s>
<s>
Two	O
processes	B-Operating_System
can	O
use	O
a	O
D-Bus	B-Language
connection	O
to	O
exchange	O
messages	O
directly	O
between	O
them	O
,	O
but	O
this	O
is	O
not	O
the	O
way	O
in	O
which	O
D-Bus	B-Language
is	O
normally	O
intended	O
to	O
be	O
used	O
.	O
</s>
<s>
as	O
a	O
communications	O
central	O
point	O
to	O
which	O
each	O
process	O
should	O
establish	O
its	O
point-to-point	O
D-Bus	B-Language
connection	O
.	O
</s>
<s>
When	O
a	O
process	O
—	O
client	O
or	O
service	O
—	O
sends	O
a	O
D-Bus	B-Language
message	O
,	O
the	O
message	B-Application
bus	I-Application
process	O
receives	O
it	O
in	O
the	O
first	O
instance	O
and	O
delivers	O
it	O
to	O
the	O
appropriate	O
recipient	O
.	O
</s>
<s>
The	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
may	O
be	O
seen	O
as	O
a	O
hub	O
or	O
router	O
in	O
charge	O
of	O
getting	O
each	O
message	O
to	O
its	O
destination	O
by	O
repeating	O
it	O
through	O
the	O
D-Bus	B-Language
connection	O
to	O
the	O
recipient	O
process	O
.	O
</s>
<s>
The	O
recipient	O
process	O
is	O
determined	O
by	O
the	O
destination	O
bus	O
name	O
in	O
the	O
message	O
's	O
header	O
field	O
,	O
or	O
by	O
the	O
subscription	O
information	O
to	O
signals	O
maintained	O
by	O
the	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
in	O
the	O
case	O
of	O
signal	O
propagation	O
messages	O
.	O
</s>
<s>
The	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
can	O
also	O
produce	O
its	O
own	O
messages	O
as	O
a	O
response	O
to	O
certain	O
conditions	O
,	O
such	O
as	O
an	O
error	O
message	O
to	O
a	O
process	O
that	O
sent	O
a	O
message	O
to	O
a	O
nonexistent	O
bus	O
name	O
.	O
</s>
<s>
improves	O
the	O
feature	O
set	O
already	O
provided	O
by	O
D-Bus	B-Language
itself	O
with	O
additional	O
functionality	O
.	O
</s>
<s>
For	O
example	O
,	O
service	O
activation	O
allows	O
automatic	O
starting	O
of	O
services	O
when	O
needed	O
—	O
when	O
the	O
first	O
request	O
to	O
any	O
bus	O
name	O
of	O
such	O
service	O
arrives	O
at	O
the	O
message	B-Application
bus	I-Application
daemon	B-Operating_System
.	O
</s>
<s>
This	O
way	O
,	O
service	O
processes	B-Operating_System
neither	O
need	O
to	O
be	O
launched	O
during	O
the	O
system	B-Operating_System
initialization	I-Operating_System
or	O
user	O
initialization	O
stage	O
nor	O
need	O
they	O
consume	O
memory	O
or	O
other	O
resources	O
when	O
not	O
being	O
used	O
.	O
</s>
<s>
This	O
feature	O
was	O
originally	O
implemented	O
using	O
setuid	O
helpers	O
,	O
but	O
nowadays	O
it	O
can	O
also	O
be	O
provided	O
by	O
systemd	B-Application
's	O
service	O
activation	O
framework	B-Architecture
.	O
</s>
<s>
D-Bus	B-Language
was	O
started	O
in	O
2002	O
by	O
Havoc	O
Pennington	O
,	O
Alex	O
Larsson	O
(	O
Red	O
Hat	O
)	O
and	O
Anders	O
Carlsson	O
.	O
</s>
<s>
The	O
version	O
1.0	O
—	O
considered	O
API	B-Application
stable	O
—	O
was	O
released	O
in	O
November	O
2006	O
.	O
</s>
<s>
Heavily	O
influenced	O
by	O
the	O
DCOP	B-Language
system	O
used	O
by	O
versions	O
2	O
and	O
3	O
of	O
KDE	B-Application
,	O
D-Bus	B-Language
has	O
replaced	O
DCOP	B-Language
in	O
the	O
KDE	B-Language
4	I-Language
release	O
.	O
</s>
<s>
An	O
implementation	O
of	O
D-Bus	B-Language
supports	O
most	O
POSIX	O
operating	B-General_Concept
systems	I-General_Concept
,	O
and	O
a	O
port	O
for	O
Windows	O
exists	O
.	O
</s>
<s>
It	O
is	O
used	O
by	O
Qt	B-Language
4	O
and	O
later	O
by	O
GNOME	B-Application
.	O
</s>
<s>
In	O
GNOME	B-Application
it	O
has	O
gradually	O
replaced	O
most	O
parts	O
of	O
the	O
earlier	O
Bonobo	B-Language
mechanism	O
.	O
</s>
<s>
It	O
is	O
also	O
used	O
by	O
Xfce	B-Language
.	O
</s>
<s>
One	O
of	O
the	O
earlier	O
adopters	O
was	O
the	O
(	O
nowadays	O
deprecated	O
)	O
Hardware	B-Application
Abstraction	I-Application
Layer	I-Application
.	O
</s>
<s>
HAL	B-Application
used	O
D-Bus	B-Language
to	O
export	O
information	O
about	O
hardware	O
that	O
has	O
been	O
added	O
to	O
or	O
removed	O
from	O
the	O
computer	O
.	O
</s>
<s>
The	O
usage	O
of	O
D-Bus	B-Language
is	O
steadily	O
expanding	O
beyond	O
the	O
initial	O
scope	O
of	O
desktop	O
environments	O
to	O
cover	O
an	O
increasing	O
amount	O
of	O
system	O
services	O
.	O
</s>
<s>
For	O
instance	O
,	O
the	O
NetworkManager	B-Protocol
network	O
daemon	B-Operating_System
,	O
BlueZ	O
bluetooth	B-Protocol
stack	O
and	O
PulseAudio	B-Library
sound	O
server	O
use	O
D-Bus	B-Language
to	O
provide	O
part	O
or	O
all	O
of	O
their	O
services	O
.	O
</s>
<s>
systemd	B-Application
uses	O
the	O
D-Bus	B-Language
wire	B-Protocol
protocol	I-Protocol
for	O
communication	O
between	O
and	O
systemd	B-Application
,	O
and	O
is	O
also	O
promoting	O
traditional	O
system	B-Operating_System
daemons	I-Operating_System
to	O
D-Bus	B-Language
services	O
,	O
such	O
as	O
logind	O
.	O
</s>
<s>
Another	O
heavy	O
user	O
of	O
D-Bus	B-Language
is	O
Polkit	B-Language
,	O
whose	O
policy	O
authority	O
daemon	B-Operating_System
is	O
implemented	O
as	O
a	O
service	O
connected	O
to	O
the	O
system	O
bus	O
.	O
</s>
<s>
Although	O
there	O
are	O
several	O
implementations	O
of	O
D-Bus	B-Language
,	O
the	O
most	O
widely	O
used	O
is	O
the	O
reference	O
implementation	O
libdbus	O
,	O
developed	O
by	O
the	O
same	O
freedesktop.org	B-Application
project	O
that	O
designed	O
the	O
specification	O
.	O
</s>
<s>
However	O
,	O
libdbus	O
is	O
a	O
low-level	O
implementation	O
that	O
was	O
never	O
meant	O
to	O
be	O
used	O
directly	O
by	O
application	O
developers	O
,	O
but	O
as	O
a	O
reference	O
guide	O
for	O
other	O
reimplementations	O
of	O
D-Bus	B-Language
(	O
such	O
as	O
those	O
included	O
in	O
standard	O
libraries	O
of	O
desktop	O
environments	O
,	O
or	O
in	O
programming	O
language	B-Application
bindings	I-Application
)	O
.	O
</s>
<s>
The	O
freedesktop.org	B-Application
project	O
itself	O
recommends	O
applications	B-Application
authors	O
to	O
"	O
use	O
one	O
of	O
the	O
higher	O
level	O
bindings	B-Application
or	O
implementations	O
"	O
instead	O
.	O
</s>
<s>
The	O
predominance	O
of	O
libdbus	O
as	O
the	O
most	O
used	O
D-Bus	B-Language
implementation	O
caused	O
the	O
terms	O
"	O
D-Bus	B-Language
"	O
and	O
"	O
libdbus	O
"	O
to	O
be	O
often	O
used	O
interchangeably	O
,	O
leading	O
to	O
confusion	O
.	O
</s>
<s>
GDBus	O
is	O
an	O
implementation	O
of	O
D-Bus	B-Language
based	O
on	O
GIO	B-Language
streams	I-Language
included	O
in	O
GLib	B-Language
,	O
aiming	O
to	O
be	O
used	O
by	O
GTK+	B-Application
and	O
GNOME	B-Application
.	O
</s>
<s>
GDBus	O
is	O
not	O
a	O
wrapper	O
of	O
libdbus	O
,	O
but	O
a	O
complete	O
and	O
independent	O
reimplementation	O
of	O
the	O
D-Bus	B-Language
specification	O
and	O
protocol	O
.	O
</s>
<s>
MATE	B-Language
Desktop	I-Language
and	O
Xfce	B-Language
(	O
version	O
4.14	O
)	O
,	O
which	O
are	O
also	O
based	O
on	O
GTK+	B-Application
3	I-Application
,	O
also	O
use	O
GDBus	O
.	O
</s>
<s>
In	O
2013	O
,	O
the	O
systemd	B-Application
project	O
rewrote	O
libdbus	O
in	O
an	O
effort	O
to	O
simplify	O
the	O
code	O
,	O
but	O
it	O
also	O
resulted	O
in	O
a	O
significant	O
increase	O
of	O
the	O
overall	O
D-Bus	B-Language
performance	O
.	O
</s>
<s>
In	O
preliminary	O
benchmarks	O
,	O
BMW	O
found	O
that	O
the	O
systemd	B-Application
's	O
D-Bus	B-Language
library	B-Library
increased	O
performance	O
by	O
360%	O
.	O
</s>
<s>
By	O
version	O
221	O
of	O
systemd	B-Application
,	O
the	O
sd-bus	O
API	B-Application
was	O
declared	O
stable	O
.	O
</s>
<s>
kdbus	O
was	O
a	O
project	O
that	O
aimed	O
to	O
reimplement	O
D-Bus	B-Language
as	O
a	O
kernel-mediated	O
peer-to-peer	O
inter-process	B-Operating_System
communication	I-Operating_System
mechanism	O
.	O
</s>
<s>
Beside	O
performance	O
improvements	O
,	O
kdbus	O
would	O
have	O
advantages	O
arising	O
from	O
other	O
Linux	B-Operating_System
kernel	I-Operating_System
features	O
such	O
as	O
namespaces	B-Architecture
and	O
auditing	O
,	O
security	O
from	O
the	O
kernel	B-Operating_System
mediating	O
,	O
closing	O
race	O
conditions	O
,	O
and	O
allowing	O
D-Bus	B-Language
to	O
be	O
used	O
during	O
boot	O
and	O
shutdown	O
(	O
as	O
needed	O
by	O
systemd	B-Application
)	O
.	O
</s>
<s>
kdbus	O
inclusion	O
in	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
proved	O
controversial	O
,	O
and	O
was	O
dropped	O
in	O
favor	O
of	O
,	O
as	O
a	O
more	O
generic	O
inter-process	B-Operating_System
communication	I-Operating_System
.	O
</s>
<s>
Several	O
programming	O
language	B-Application
bindings	I-Application
for	O
D-Bus	B-Language
have	O
been	O
developed	O
,	O
such	O
as	O
those	O
for	O
Java	B-Language
,	O
C#	B-Application
,	O
Ruby	B-Language
,	O
and	O
Perl	B-Language
.	O
</s>
