<s>
A	O
Unix	B-Protocol
domain	I-Protocol
socket	I-Protocol
aka	O
UDS	O
or	O
IPC	B-Protocol
socket	I-Protocol
(	O
inter-process	B-Operating_System
communication	I-Operating_System
socket	O
)	O
is	O
a	O
data	O
communications	B-Protocol
endpoint	I-Protocol
for	O
exchanging	O
data	O
between	O
processes	O
executing	O
on	O
the	O
same	O
host	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
Unix	B-Protocol
domain	I-Protocol
socket	I-Protocol
facility	O
is	O
a	O
standard	O
component	O
of	O
POSIX	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
The	O
API	B-General_Concept
for	O
Unix	B-Protocol
domain	I-Protocol
sockets	I-Protocol
is	O
similar	O
to	O
that	O
of	O
an	O
Internet	B-Protocol
socket	I-Protocol
,	O
but	O
rather	O
than	O
using	O
an	O
underlying	O
network	O
protocol	O
,	O
all	O
communication	O
occurs	O
entirely	O
within	O
the	O
operating	B-Operating_System
system	I-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
Unix	B-Protocol
domain	I-Protocol
sockets	I-Protocol
may	O
use	O
the	O
file	O
system	O
as	O
their	O
address	O
name	O
space	O
.	O
</s>
<s>
(	O
Some	O
operating	B-General_Concept
systems	I-General_Concept
,	O
like	O
Linux	B-Application
,	O
offer	O
additional	O
namespaces	O
.	O
)	O
</s>
<s>
Processes	O
reference	O
Unix	B-Protocol
domain	I-Protocol
sockets	I-Protocol
as	O
file	O
system	O
inodes	B-Application
,	O
so	O
two	O
processes	O
can	O
communicate	O
by	O
opening	O
the	O
same	O
socket	O
.	O
</s>
<s>
In	O
addition	O
to	O
sending	O
data	O
,	O
processes	O
may	O
send	O
file	B-Application
descriptors	I-Application
across	O
a	O
Unix	B-Protocol
domain	I-Protocol
socket	I-Protocol
connection	O
using	O
the	O
sendmsg( )	O
and	O
recvmsg( )	O
system	O
calls	O
.	O
</s>
<s>
This	O
allows	O
the	O
sending	O
processes	O
to	O
grant	O
the	O
receiving	O
process	O
access	O
to	O
a	O
file	B-Application
descriptor	I-Application
for	O
which	O
the	O
receiving	O
process	O
otherwise	O
does	O
not	O
have	O
access	O
.	O
</s>
