<s>
File	B-Protocol
Service	I-Protocol
Protocol	I-Protocol
(	O
FSP	O
)	O
is	O
a	O
UDP-based	O
replacement	O
for	O
the	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
,	O
designed	O
for	O
anonymous	O
access	O
with	O
lower	O
hardware	O
and	O
network	O
requirements	O
than	O
FTP	O
.	O
</s>
<s>
In	O
particular	O
,	O
because	O
it	O
uses	O
UDP	B-Protocol
,	O
it	O
avoids	O
the	O
problems	O
that	O
many	O
FTP	O
servers	O
have	O
had	O
with	O
requiring	O
a	O
separate	O
process	O
for	O
each	O
client	O
,	O
and	O
because	O
it	O
is	O
built	O
to	O
use	O
an	O
unreliable	O
protocol	O
,	O
it	O
can	O
more	O
easily	O
handle	O
resuming	O
a	O
transfer	O
after	O
a	O
network	O
failure	O
.	O
</s>
<s>
FSP	O
never	O
reached	O
the	O
popularity	O
of	O
FTP	O
for	O
legitimate	O
use	O
(	O
although	O
wuarchive	B-Protocol
and	O
id	O
Software	O
provided	O
FSP	O
service	O
in	O
addition	O
to	O
FTP	O
for	O
some	O
time	O
)	O
,	O
but	O
became	O
very	O
popular	O
in	O
the	O
early-to-mid-1990s	O
for	O
underground	B-Operating_System
sites	O
containing	O
pornography	O
and/or	O
warez	B-Application
.	O
</s>
<s>
Because	O
an	O
FSP	O
server	O
only	O
requires	O
one	O
process	O
(	O
as	O
opposed	O
to	O
one	O
process	O
per	O
client	O
for	O
most	O
FTP	O
servers	O
)	O
,	O
it	O
is	O
much	O
harder	O
for	O
a	O
system	B-Application
administrator	I-Application
to	O
notice	O
it	O
in	O
a	O
process	O
list	O
;	O
also	O
,	O
since	O
it	O
uses	O
UDP	B-Protocol
,	O
it	O
is	O
less	O
likely	O
to	O
be	O
noticed	O
by	O
a	O
network	O
administrator	O
.	O
</s>
<s>
Eventually	O
,	O
however	O
,	O
an	O
increased	O
use	O
of	O
firewalls	B-Application
,	O
a	O
decreasing	O
usage	O
of	O
the	O
shell	O
accounts	O
required	O
to	O
run	O
a	O
server	O
or	O
most	O
of	O
the	O
clients	O
,	O
and	O
a	O
lack	O
of	O
FSP	O
support	O
in	O
web	B-Application
browsers	I-Application
caused	O
its	O
use	O
to	O
taper	O
off	O
,	O
and	O
the	O
warez	B-Application
scene	I-Application
moved	O
to	O
HTTP	B-Protocol
and	O
FXP	B-Protocol
while	O
pornography	O
moved	O
to	O
publicly	O
advertised	O
web	B-Application
servers	I-Application
.	O
</s>
<s>
As	O
the	O
FSP	B-Protocol
protocol	I-Protocol
is	O
not	O
officially	O
recognized	O
by	O
IANA	O
,	O
it	O
has	O
no	O
official	O
port	B-Protocol
number	I-Protocol
.	O
</s>
<s>
However	O
,	O
as	O
a	O
UDP	B-Protocol
equivalent	O
of	O
FTP	O
,	O
official	O
FSP	O
servers	O
frequently	O
run	O
on	O
UDP	B-Protocol
port	I-Protocol
21	O
,	O
which	O
is	O
the	O
same	O
as	O
FTP	O
's	O
TCP	O
port	B-Protocol
number	I-Protocol
.	O
</s>
<s>
Because	O
FSP	O
uses	O
UDP	B-Protocol
and	O
FTP	O
uses	O
TCP	O
they	O
can	O
both	O
run	O
at	O
same	O
time	O
on	O
the	O
same	O
port	B-Protocol
number	I-Protocol
without	O
conflict	O
.	O
</s>
<s>
(	O
On	O
most	O
*	B-Operating_System
nix	I-Operating_System
systems	O
,	O
only	O
the	O
root	B-Application
user	I-Application
can	O
start	O
a	O
process	O
that	O
listens	O
on	O
a	O
port	O
under	O
1024	O
.	O
)	O
</s>
<s>
In	O
1993	O
,	O
discussions	O
were	O
held	O
about	O
what	O
to	O
expand	O
the	O
acronym	O
to	O
;	O
the	O
ultimate	O
result	O
was	O
File	B-Protocol
Service	I-Protocol
Protocol	I-Protocol
.	O
</s>
