<s>
Desktop	B-Language
Communication	I-Language
Protocol	I-Language
(	O
DCOP	B-Language
)	O
was	O
an	O
inter-process	B-Operating_System
communication	I-Operating_System
(	O
IPC	O
)	O
daemon	B-Operating_System
by	O
KDE	B-Application
used	O
in	O
K	B-Language
Desktop	I-Language
Environment	I-Language
3	I-Language
.	O
</s>
<s>
The	O
design	O
goal	O
for	O
the	O
protocol	O
was	O
to	O
allow	O
applications	B-Application
to	O
interoperate	O
,	O
and	O
share	O
complex	O
tasks	O
.	O
</s>
<s>
Essentially	O
,	O
DCOP	B-Language
was	O
a	O
‘	O
remote	O
control’	O
system	O
,	O
which	O
allowed	O
applications	B-Application
or	O
scripts	O
to	O
enlist	O
the	O
help	O
of	O
other	O
applications	B-Application
.	O
</s>
<s>
DCOP	B-Language
is	O
built	O
on	O
top	O
of	O
the	O
X11	O
Inter-Client	O
Exchange	O
protocol	O
.	O
</s>
<s>
DCOP	B-Language
continues	O
to	O
be	O
used	O
by	O
the	O
K	O
Desktop	O
Environment	O
3-fork	O
Trinity	B-Application
Desktop	I-Application
Environment	I-Application
.	O
</s>
<s>
DCOP	B-Language
was	O
replaced	O
by	O
D-Bus	B-Language
,	O
a	O
message	O
bus	O
system	O
heavily	O
influenced	O
by	O
the	O
DCOP	B-Language
and	O
standardized	O
by	O
freedesktop.org,	O
in	O
KDE	B-Language
Software	I-Language
Compilation	I-Language
4	I-Language
and	O
later	O
.	O
</s>
<s>
DCOP	B-Language
implements	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
,	O
where	O
each	O
application	O
using	O
DCOP	B-Language
is	O
a	O
client	O
and	O
communicates	O
with	O
other	O
clients	O
through	O
the	O
DCOP	B-Language
server	O
.	O
</s>
<s>
DCOP	B-Language
server	O
functions	O
like	O
a	O
traffic	O
director	O
,	O
dispatching	O
messages/calls	O
to	O
the	O
proper	O
destinations	O
.	O
</s>
<s>
Two	O
types	O
of	O
actions	O
are	O
possible	O
with	O
DCOP	B-Language
:	O
"	O
send	O
and	O
forget	O
"	O
messages	O
,	O
which	O
do	O
not	O
block	O
,	O
and	O
"	O
calls	O
,	O
"	O
which	O
block	O
waiting	O
for	O
some	O
data	O
to	O
be	O
returned	O
.	O
</s>
<s>
Any	O
data	O
that	O
will	O
be	O
sent	O
is	O
serialized	O
(	O
also	O
referred	O
to	O
as	O
marshalling	B-Application
in	O
CORBA	B-Architecture
speak	O
)	O
using	O
the	O
built-in	O
QDataStream	O
operators	O
available	O
in	O
all	O
of	O
the	O
Qt	B-Language
classes	O
.	O
</s>
<s>
Using	O
the	O
dcopidl	O
compiler	O
has	O
the	O
additional	O
benefit	O
of	O
type	B-Language
safety	I-Language
.	O
</s>
<s>
There	O
is	O
a	O
command-line	O
tool	O
called	O
‘	O
dcop’	O
(	O
note	O
the	O
lower-case	O
letters	O
)	O
that	O
can	O
be	O
used	O
for	O
communication	O
with	O
the	O
applications	B-Application
from	O
the	O
shell	O
.	O
</s>
<s>
‘	O
kdcop’	O
is	O
a	O
GUI	B-Application
tool	O
to	O
explore	O
the	O
interfaces	B-Application
of	O
an	O
application	O
.	O
</s>
