<s>
The	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
FTP	B-Protocol
)	O
is	O
a	O
standard	O
communication	O
protocol	O
used	O
for	O
the	O
transfer	O
of	O
computer	B-Operating_System
files	I-Operating_System
from	O
a	O
server	B-Application
to	O
a	O
client	B-Protocol
on	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
FTP	B-Protocol
is	O
built	O
on	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
architecture	O
using	O
separate	O
control	O
and	O
data	O
connections	O
between	O
the	O
client	B-Protocol
and	O
the	O
server	B-Application
.	O
</s>
<s>
FTP	B-Protocol
users	O
may	O
authenticate	O
themselves	O
with	O
a	O
clear-text	O
sign-in	O
protocol	O
,	O
normally	O
in	O
the	O
form	O
of	O
a	O
username	O
and	O
password	O
,	O
but	O
can	O
connect	O
anonymously	O
if	O
the	O
server	B-Application
is	O
configured	O
to	O
allow	O
it	O
.	O
</s>
<s>
For	O
secure	O
transmission	O
that	O
protects	O
the	O
username	O
and	O
password	O
,	O
and	O
encrypts	O
the	O
content	O
,	O
FTP	B-Protocol
is	O
often	O
secured	O
with	O
SSL/TLS	B-Protocol
(	O
FTPS	B-Protocol
)	O
or	O
replaced	O
with	O
SSH	B-Protocol
File	I-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
SFTP	O
)	O
.	O
</s>
<s>
The	O
first	O
FTP	B-Protocol
client	I-Protocol
applications	O
were	O
command-line	B-Application
programs	I-Application
developed	O
before	O
operating	B-General_Concept
systems	I-General_Concept
had	O
graphical	B-Application
user	I-Application
interfaces	I-Application
,	O
and	O
are	O
still	O
shipped	O
with	O
most	O
Windows	O
,	O
Unix	B-Application
,	O
and	O
Linux	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
Many	O
dedicated	O
FTP	B-Protocol
clients	I-Protocol
and	O
automation	O
utilities	O
have	O
since	O
been	O
developed	O
for	O
desktops	B-Device
,	O
servers	O
,	O
mobile	O
devices	O
,	O
and	O
hardware	O
,	O
and	O
FTP	B-Protocol
has	O
been	O
incorporated	O
into	O
productivity	O
applications	O
such	O
as	O
HTML	B-General_Concept
editors	I-General_Concept
and	O
file	B-Application
managers	I-Application
.	O
</s>
<s>
An	O
FTP	B-Protocol
client	I-Protocol
used	O
to	O
be	O
commonly	O
integrated	O
in	O
web	B-Application
browsers	I-Application
,	O
where	O
file	O
servers	O
are	O
browsed	O
with	O
the	O
URI	B-Protocol
prefix	O
"	O
ftp://	B-Protocol
"	O
.	O
</s>
<s>
Throughout	O
2021	O
,	O
the	O
two	O
major	O
web	B-Application
browser	I-Application
vendors	O
removed	O
this	O
ability	O
.	O
</s>
<s>
Support	O
for	O
the	O
FTP	B-Protocol
protocol	I-Protocol
was	O
first	O
disabled	O
in	O
Google	O
Chrome	O
88	O
in	O
January	O
2021	O
,	O
followed	O
by	O
Firefox	B-Application
88.0	O
in	O
April	O
2021	O
.	O
</s>
<s>
In	O
July	O
2021	O
,	O
Firefox	B-Application
90	O
dropped	O
FTP	B-Protocol
entirely	O
,	O
and	O
Google	O
followed	O
suit	O
in	O
October	O
2021	O
,	O
removing	O
FTP	B-Protocol
entirely	O
in	O
Google	O
Chrome	O
95	O
.	O
</s>
<s>
The	O
original	O
specification	O
for	O
the	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
was	O
written	O
by	O
Abhay	O
Bhushan	O
and	O
published	O
as	O
on	O
16	O
April	O
1971	O
.	O
</s>
<s>
Until	O
1980	O
,	O
FTP	B-Protocol
ran	O
on	O
NCP	B-Protocol
,	O
the	O
predecessor	O
of	O
TCP/IP	B-Protocol
.	O
</s>
<s>
The	O
protocol	O
was	O
later	O
replaced	O
by	O
a	O
TCP/IP	B-Protocol
version	O
,	O
(	O
June	O
1980	O
)	O
and	O
(	O
October	O
1985	O
)	O
,	O
the	O
current	O
specification	O
.	O
</s>
<s>
Several	O
proposed	O
standards	O
amend	O
,	O
for	O
example	O
(	O
February	O
1994	O
)	O
enables	O
Firewall-Friendly	O
FTP	B-Protocol
(	O
passive	O
mode	O
)	O
,	O
(	O
June	O
1997	O
)	O
proposes	O
security	O
extensions	O
,	O
(	O
September	O
1998	O
)	O
adds	O
support	O
for	O
IPv6	B-Protocol
and	O
defines	O
a	O
new	O
type	O
of	O
passive	O
mode	O
.	O
</s>
<s>
FTP	B-Protocol
may	O
run	O
in	O
active	O
or	O
passive	O
mode	O
,	O
which	O
determines	O
how	O
the	O
data	O
connection	O
is	O
established	O
.	O
</s>
<s>
(	O
This	O
sense	O
of	O
"	O
mode	O
"	O
is	O
different	O
from	O
that	O
of	O
the	O
MODE	O
command	O
in	O
the	O
FTP	B-Protocol
protocol	I-Protocol
.	O
)	O
</s>
<s>
In	O
active	O
mode	O
,	O
the	O
client	B-Protocol
starts	O
listening	O
for	O
incoming	O
data	O
connections	O
from	O
the	O
server	B-Application
on	O
port	O
M	O
.	O
It	O
sends	O
the	O
FTP	B-Protocol
command	O
PORT	O
M	O
to	O
inform	O
the	O
server	B-Application
on	O
which	O
port	O
it	O
is	O
listening	O
.	O
</s>
<s>
The	O
server	B-Application
then	O
initiates	O
a	O
data	O
channel	O
to	O
the	O
client	B-Protocol
from	O
its	O
port	O
20	O
,	O
the	O
FTP	B-Protocol
server	I-Protocol
data	O
port	O
.	O
</s>
<s>
In	O
situations	O
where	O
the	O
client	B-Protocol
is	O
behind	O
a	O
firewall	B-Application
and	O
unable	O
to	O
accept	O
incoming	O
TCP	B-Protocol
connections	O
,	O
passive	O
mode	O
may	O
be	O
used	O
.	O
</s>
<s>
In	O
this	O
mode	O
,	O
the	O
client	B-Protocol
uses	O
the	O
control	O
connection	O
to	O
send	O
a	O
PASV	O
command	O
to	O
the	O
server	B-Application
and	O
then	O
receives	O
a	O
server	B-Application
IP	O
address	O
and	O
server	B-Application
port	O
number	O
from	O
the	O
server	B-Application
,	O
which	O
the	O
client	B-Protocol
then	O
uses	O
to	O
open	O
a	O
data	O
connection	O
from	O
an	O
arbitrary	O
client	B-Protocol
port	O
to	O
the	O
server	B-Application
IP	O
address	O
and	O
server	B-Application
port	O
number	O
received	O
.	O
</s>
<s>
Both	O
modes	O
were	O
updated	O
in	O
September	O
1998	O
to	O
support	O
IPv6	B-Protocol
.	O
</s>
<s>
The	O
server	B-Application
responds	O
over	O
the	O
control	O
connection	O
with	O
three-digit	B-Protocol
status	I-Protocol
codes	I-Protocol
in	O
ASCII	B-Protocol
with	O
an	O
optional	O
text	O
message	O
.	O
</s>
<s>
FTP	B-Protocol
needs	O
two	O
ports	O
(	O
one	O
for	O
sending	O
and	O
one	O
for	O
receiving	O
)	O
because	O
it	O
was	O
originally	O
designed	O
to	O
operate	O
on	O
top	O
of	O
Network	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
NCP	B-Protocol
)	O
,	O
which	O
was	O
a	O
simplex	O
protocol	O
that	O
utilized	O
two	O
port	B-Protocol
addresses	I-Protocol
,	O
establishing	O
two	O
connections	O
,	O
for	O
two-way	O
communications	O
.	O
</s>
<s>
An	O
odd	O
and	O
an	O
even	O
port	O
were	O
reserved	O
for	O
each	O
application	B-Application
layer	I-Application
application	O
or	O
protocol	O
.	O
</s>
<s>
The	O
standardization	O
of	O
TCP	B-Protocol
and	O
UDP	O
reduced	O
the	O
need	O
for	O
the	O
use	O
of	O
two	O
simplex	O
ports	O
for	O
each	O
application	O
down	O
to	O
one	O
duplex	O
port	O
,	O
but	O
the	O
FTP	B-Protocol
protocol	I-Protocol
was	O
never	O
altered	O
to	O
only	O
use	O
one	O
port	O
,	O
and	O
continued	O
using	O
two	O
for	O
backwards	O
compatibility	O
.	O
</s>
<s>
FTP	B-Protocol
normally	O
transfers	O
data	O
by	O
having	O
the	O
server	B-Application
connect	O
back	O
to	O
the	O
client	B-Protocol
,	O
after	O
the	O
PORT	O
command	O
is	O
sent	O
by	O
the	O
client	B-Protocol
.	O
</s>
<s>
This	O
is	O
problematic	O
for	O
both	O
NATs	B-Protocol
and	O
firewalls	B-Application
,	O
which	O
do	O
not	O
allow	O
connections	O
from	O
the	O
Internet	O
towards	O
internal	O
hosts	O
.	O
</s>
<s>
For	O
NATs	B-Protocol
,	O
an	O
additional	O
complication	O
is	O
that	O
the	O
representation	O
of	O
the	O
IP	O
addresses	O
and	O
port	O
number	O
in	O
the	O
PORT	O
command	O
refer	O
to	O
the	O
internal	O
host	O
's	O
IP	O
address	O
and	O
port	O
,	O
rather	O
than	O
the	O
public	O
IP	O
address	O
and	O
port	O
of	O
the	O
NAT	O
.	O
</s>
<s>
One	O
is	O
that	O
the	O
FTP	B-Protocol
client	I-Protocol
and	O
FTP	B-Protocol
server	I-Protocol
use	O
the	O
PASV	O
command	O
,	O
which	O
causes	O
the	O
data	O
connection	O
to	O
be	O
established	O
from	O
the	O
FTP	B-Protocol
client	I-Protocol
to	O
the	O
server	B-Application
.	O
</s>
<s>
This	O
is	O
widely	O
used	O
by	O
modern	O
FTP	B-Protocol
clients	I-Protocol
.	O
</s>
<s>
ASCII	B-Protocol
(	O
TYPE	O
A	O
)	O
:	O
Used	O
for	O
text	O
.	O
</s>
<s>
Data	O
is	O
converted	O
,	O
if	O
needed	O
,	O
from	O
the	O
sending	O
host	O
's	O
character	O
representation	O
to	O
"	B-Protocol
8-bit	I-Protocol
ASCII	I-Protocol
"	I-Protocol
before	O
transmission	O
,	O
and	O
(	O
again	O
,	O
if	O
necessary	O
)	O
to	O
the	O
receiving	O
host	O
's	O
character	O
representation	O
,	O
including	O
newlines	O
.	O
</s>
<s>
As	O
a	O
consequence	O
,	O
this	O
mode	O
is	O
inappropriate	O
for	O
files	O
that	O
contain	O
data	O
other	O
than	O
ASCII	B-Protocol
.	O
</s>
<s>
Image	O
(	O
TYPE	O
I	O
,	O
commonly	O
called	O
Binary	O
mode	O
)	O
:	O
The	O
sending	O
machine	O
sends	O
each	O
file	O
byte	B-Application
by	O
byte	B-Application
,	O
and	O
the	O
recipient	O
stores	O
the	O
bytestream	O
as	O
it	O
receives	O
it	O
.	O
</s>
<s>
(	O
Image	O
mode	O
support	O
has	O
been	O
recommended	O
for	O
all	O
implementations	O
of	O
FTP	B-Protocol
)	O
.	O
</s>
<s>
EBCDIC	B-Language
(	O
TYPE	O
E	O
)	O
:	O
Used	O
for	O
plain	O
text	O
between	O
hosts	O
using	O
the	O
EBCDIC	B-Language
character	O
set	O
.	O
</s>
<s>
Local	O
(	O
TYPE	O
L	O
n	O
)	O
:	O
Designed	O
to	O
support	O
file	B-Protocol
transfer	I-Protocol
between	O
machines	O
which	O
do	O
not	O
use	O
8-bit	O
bytes	B-Application
,	O
e.g.	O
</s>
<s>
36-bit	O
systems	O
such	O
as	O
DEC	B-Device
PDP-10s	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
"	O
TYPE	O
L	O
9	O
"	O
would	O
be	O
used	O
to	O
transfer	O
data	O
in	O
9-bit	O
bytes	B-Application
,	O
or	O
"	O
TYPE	O
L	O
36	O
"	O
to	O
transfer	O
36-bit	O
words	O
.	O
</s>
<s>
Note	O
these	O
data	O
types	O
are	O
commonly	O
called	O
"	O
modes	O
"	O
,	O
although	O
ambiguously	O
that	O
word	O
is	O
also	O
used	O
to	O
refer	O
to	O
active-vs-passive	O
communication	O
mode	O
(	O
see	O
above	O
)	O
,	O
and	O
the	O
modes	O
set	O
by	O
the	O
FTP	B-Protocol
protocol	I-Protocol
MODE	O
command	O
(	O
see	O
below	O
)	O
.	O
</s>
<s>
Files	O
are	O
viewed	O
as	O
an	O
arbitrary	O
sequence	O
of	O
bytes	B-Application
,	O
characters	O
or	O
words	O
.	O
</s>
<s>
This	O
is	O
the	O
usual	O
file	O
structure	O
on	O
Unix	B-Application
systems	I-Application
and	O
other	O
systems	O
such	O
as	O
CP/M	O
,	O
MS-DOS	O
and	O
Microsoft	O
Windows	O
.	O
</s>
<s>
This	O
file	O
organization	O
is	O
common	O
on	O
mainframe	O
and	O
midrange	O
systems	O
,	O
such	O
as	O
MVS	O
,	O
VM/CMS	O
,	O
OS/400	O
and	O
VMS	O
,	O
which	O
support	O
record-oriented	B-Application
filesystems	I-Application
.	O
</s>
<s>
This	O
file	O
structure	O
was	O
specifically	O
designed	O
for	O
TENEX	B-Operating_System
systems	O
,	O
and	O
is	O
generally	O
not	O
supported	O
on	O
other	O
platforms	O
.	O
</s>
<s>
Most	O
contemporary	O
FTP	B-Protocol
clients	I-Protocol
and	O
servers	O
only	O
support	O
STRU	O
F	O
.	O
STRU	O
R	O
is	O
still	O
in	O
use	O
in	O
mainframe	O
and	O
minicomputer	O
file	B-Protocol
transfer	I-Protocol
applications	O
.	O
</s>
<s>
Stream	O
mode	O
(	O
MODE	O
S	O
)	O
:	O
Data	O
is	O
sent	O
as	O
a	O
continuous	O
stream	O
,	O
relieving	O
FTP	B-Protocol
from	O
doing	O
any	O
processing	O
.	O
</s>
<s>
Rather	O
,	O
all	O
processing	O
is	O
left	O
up	O
to	O
TCP	B-Protocol
.	O
</s>
<s>
Block	O
mode	O
(	O
MODE	O
B	O
)	O
:	O
Designed	O
primarily	O
for	O
transferring	O
record-oriented	B-Application
files	I-Application
(	O
STRU	O
R	O
)	O
,	O
although	O
can	O
also	O
be	O
used	O
to	O
transfer	O
stream-oriented	O
(	O
STRU	O
F	O
)	O
text	O
files	O
.	O
</s>
<s>
FTP	B-Protocol
puts	O
each	O
record	O
(	O
or	O
line	O
)	O
of	O
data	O
into	O
several	O
blocks	O
(	O
block	O
header	O
,	O
byte	B-Application
count	O
,	O
and	O
data	O
field	O
)	O
and	O
then	O
passes	O
it	O
on	O
to	O
TCP	B-Protocol
.	O
</s>
<s>
Compressed	O
mode	O
(	O
MODE	O
C	O
)	O
:	O
Extends	O
MODE	O
B	O
with	O
data	O
compression	O
using	O
run-length	B-Algorithm
encoding	I-Algorithm
.	O
</s>
<s>
Most	O
contemporary	O
FTP	B-Protocol
clients	I-Protocol
and	O
servers	O
do	O
not	O
implement	O
MODE	O
B	O
or	O
MODE	O
C	O
;	O
FTP	B-Protocol
clients	I-Protocol
and	O
servers	O
for	O
mainframe	O
and	O
minicomputer	O
operating	B-General_Concept
systems	I-General_Concept
are	O
the	O
exception	O
to	O
that	O
.	O
</s>
<s>
Some	O
FTP	B-Protocol
software	O
also	O
implements	O
a	O
DEFLATE-based	O
compressed	O
mode	O
,	O
sometimes	O
called	O
"	O
Mode	O
Z	O
"	O
after	O
the	O
command	O
that	O
enables	O
it	O
.	O
</s>
<s>
GridFTP	B-Application
defines	O
additional	O
modes	O
,	O
MODE	O
E	O
and	O
MODE	O
X	O
,	O
as	O
extensions	O
of	O
MODE	O
B	O
.	O
</s>
<s>
More	O
recent	O
implementations	O
of	O
FTP	B-Protocol
support	O
the	O
Modify	O
Fact	O
:	O
Modification	O
Time	O
(	O
MFMT	O
)	O
command	O
,	O
which	O
allows	O
a	O
client	B-Protocol
to	O
adjust	O
that	O
file	B-Application
attribute	I-Application
remotely	O
,	O
enabling	O
the	O
preservation	O
of	O
that	O
attribute	O
when	O
uploading	O
files	O
.	O
</s>
<s>
FTP	B-Protocol
login	O
uses	O
normal	O
username	O
and	O
password	O
scheme	O
for	O
granting	O
access	O
.	O
</s>
<s>
The	O
username	O
is	O
sent	O
to	O
the	O
server	B-Application
using	O
the	O
USER	O
command	O
,	O
and	O
the	O
password	O
is	O
sent	O
using	O
the	O
PASS	O
command	O
.	O
</s>
<s>
This	O
sequence	O
is	O
unencrypted	O
"	O
on	O
the	O
wire	O
"	O
,	O
so	O
may	O
be	O
vulnerable	O
to	O
a	O
network	O
sniffing	B-Protocol
attack	O
.	O
</s>
<s>
If	O
the	O
information	O
provided	O
by	O
the	O
client	B-Protocol
is	O
accepted	O
by	O
the	O
server	B-Application
,	O
the	O
server	B-Application
will	O
send	O
a	O
greeting	O
to	O
the	O
client	B-Protocol
and	O
the	O
session	O
will	O
commence	O
.	O
</s>
<s>
If	O
the	O
server	B-Application
supports	O
it	O
,	O
users	O
may	O
log	O
in	O
without	O
providing	O
login	O
credentials	O
,	O
but	O
the	O
same	O
server	B-Application
may	O
authorize	O
only	O
limited	O
access	O
for	O
such	O
sessions	O
.	O
</s>
<s>
A	O
host	O
that	O
provides	O
an	O
FTP	B-Protocol
service	O
may	O
provide	O
anonymous	O
FTP	B-Protocol
access	I-Protocol
.	O
</s>
<s>
Users	O
typically	O
log	O
into	O
the	O
service	O
with	O
an	O
'	O
anonymous	O
 '	O
(	O
lower-case	O
and	O
case-sensitive	O
in	O
some	O
FTP	B-Protocol
servers	I-Protocol
)	O
account	O
when	O
prompted	O
for	O
user	O
name	O
.	O
</s>
<s>
Many	O
FTP	B-Protocol
hosts	O
whose	O
purpose	O
is	O
to	O
provide	O
software	O
updates	O
will	O
allow	O
anonymous	O
logins	O
.	O
</s>
<s>
HTTP	B-Protocol
essentially	O
fixes	O
the	O
bugs	O
in	O
FTP	B-Protocol
that	O
made	O
it	O
inconvenient	O
to	O
use	O
for	O
many	O
small	O
ephemeral	O
transfers	O
as	O
are	O
typical	O
in	O
web	O
pages	O
.	O
</s>
<s>
FTP	B-Protocol
has	O
a	O
stateful	O
control	O
connection	O
which	O
maintains	O
a	O
current	O
working	O
directory	O
and	O
other	O
flags	O
,	O
and	O
each	O
transfer	O
requires	O
a	O
secondary	O
connection	O
through	O
which	O
the	O
data	O
are	O
transferred	O
.	O
</s>
<s>
In	O
"	O
passive	O
"	O
mode	O
this	O
secondary	O
connection	O
is	O
from	O
client	B-Protocol
to	O
server	B-Application
,	O
whereas	O
in	O
the	O
default	O
"	O
active	O
"	O
mode	O
this	O
connection	O
is	O
from	O
server	B-Application
to	O
client	B-Protocol
.	O
</s>
<s>
This	O
apparent	O
role	O
reversal	O
when	O
in	O
active	O
mode	O
,	O
and	O
random	O
port	O
numbers	O
for	O
all	O
transfers	O
,	O
is	O
why	O
firewalls	B-Application
and	O
NAT	O
gateways	O
have	O
such	O
a	O
hard	O
time	O
with	O
FTP	B-Protocol
.	O
</s>
<s>
HTTP	B-Protocol
is	O
stateless	B-Protocol
and	O
multiplexes	O
control	O
and	O
data	O
over	O
a	O
single	O
connection	O
from	O
client	B-Protocol
to	O
server	B-Application
on	O
well-known	O
port	O
numbers	O
,	O
which	O
trivially	O
passes	O
through	O
NAT	O
gateways	O
and	O
is	O
simple	O
for	O
firewalls	B-Application
to	O
manage	O
.	O
</s>
<s>
Setting	O
up	O
an	O
FTP	B-Protocol
control	O
connection	O
is	O
quite	O
slow	O
due	O
to	O
the	O
round-trip	O
delays	O
of	O
sending	O
all	O
of	O
the	O
required	O
commands	O
and	O
awaiting	O
responses	O
,	O
so	O
it	O
is	O
customary	O
to	O
bring	O
up	O
a	O
control	O
connection	O
and	O
hold	O
it	O
open	O
for	O
multiple	O
file	B-Protocol
transfers	I-Protocol
rather	O
than	O
drop	O
and	O
re-establish	O
the	O
session	O
afresh	O
each	O
time	O
.	O
</s>
<s>
In	O
contrast	O
,	O
HTTP	B-Protocol
originally	O
dropped	O
the	O
connection	O
after	O
each	O
transfer	O
because	O
doing	O
so	O
was	O
so	O
cheap	O
.	O
</s>
<s>
While	O
HTTP	B-Protocol
has	O
subsequently	O
gained	O
the	O
ability	O
to	O
reuse	O
the	O
TCP	B-Protocol
connection	O
for	O
multiple	O
transfers	O
,	O
the	O
conceptual	O
model	O
is	O
still	O
of	O
independent	O
requests	O
rather	O
than	O
a	O
session	O
.	O
</s>
<s>
When	O
FTP	B-Protocol
is	O
transferring	O
over	O
the	O
data	O
connection	O
,	O
the	O
control	O
connection	O
is	O
idle	O
.	O
</s>
<s>
If	O
the	O
transfer	O
takes	O
too	O
long	O
,	O
the	O
firewall	B-Application
or	O
NAT	O
may	O
decide	O
that	O
the	O
control	O
connection	O
is	O
dead	O
and	O
stop	O
tracking	O
it	O
,	O
effectively	O
breaking	O
the	O
connection	O
and	O
confusing	O
the	O
download	O
.	O
</s>
<s>
The	O
single	O
HTTP	B-Protocol
connection	O
is	O
only	O
idle	O
between	O
requests	O
and	O
it	O
is	O
normal	O
and	O
expected	O
for	O
such	O
connections	O
to	O
be	O
dropped	O
after	O
a	O
time-out	O
.	O
</s>
<s>
Most	O
common	O
web	B-Application
browsers	I-Application
can	O
retrieve	O
files	O
hosted	O
on	O
FTP	B-Protocol
servers	I-Protocol
,	O
although	O
they	O
may	O
not	O
support	O
protocol	O
extensions	O
such	O
as	O
FTPS	B-Protocol
.	O
</s>
<s>
When	O
an	O
FTP	B-Protocol
—	O
rather	O
than	O
an	O
HTTP	B-Protocol
—	O
URL	O
is	O
supplied	O
,	O
the	O
accessible	O
contents	O
on	O
the	O
remote	O
server	B-Application
are	O
presented	O
in	O
a	O
manner	O
that	O
is	O
similar	O
to	O
that	O
used	O
for	O
other	O
web	O
content	O
.	O
</s>
<s>
FireFTP	B-Application
is	O
a	O
browser	B-Application
extension	O
designed	O
as	O
a	O
full-featured	O
FTP	B-Protocol
client	I-Protocol
,	O
it	O
could	O
be	O
run	O
within	O
Firefox	B-Application
in	O
the	O
past	O
,	O
but	O
it	O
's	O
now	O
recommend	O
working	O
with	O
Waterfox	B-Language
.	O
</s>
<s>
Google	O
Chrome	O
removed	O
FTP	B-Protocol
support	O
entirely	O
in	O
Chrome	O
88	O
.	O
</s>
<s>
As	O
of	O
2019	O
,	O
Mozilla	O
was	O
discussing	O
proposals	O
,	O
including	O
only	O
removing	O
support	O
for	O
old	O
FTP	B-Protocol
implementations	O
that	O
are	O
no	O
longer	O
in	O
use	O
to	O
simplify	O
their	O
code	O
.	O
</s>
<s>
In	O
April	O
,	O
2021	O
,	O
Mozilla	O
released	O
Firefox	B-Application
88.0	O
which	O
disabled	O
FTP	B-Protocol
support	O
by	O
default	O
.	O
</s>
<s>
In	O
July	O
2021	O
,	O
Firefox	B-Application
90	O
dropped	O
FTP	B-Protocol
support	O
entirely	O
.	O
</s>
<s>
FTP	B-Protocol
URL	O
syntax	O
is	O
described	O
in	O
,	O
taking	O
the	O
form	O
:	O
ftp://[user[:password]@]host[:port]/[url-path]	O
(	O
the	O
bracketed	O
parts	O
are	O
optional	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
URL	O
ftp://public.ftp-servers.example.com/mydirectory/myfile.txt	O
represents	O
the	O
file	O
myfile.txt	O
from	O
the	O
directory	O
mydirectory	O
on	O
the	O
server	B-Application
public.ftp-servers.example.com	O
as	O
an	O
FTP	B-Protocol
resource	O
.	O
</s>
<s>
The	O
URL	O
ftp://user001:secretpassword	O
@private	O
.ftp-servers.example.com/mydirectory/myfile.txt	O
adds	O
a	O
specification	O
of	O
the	O
username	O
and	O
password	O
that	O
must	O
be	O
used	O
to	O
access	O
this	O
resource	O
.	O
</s>
<s>
More	O
details	O
on	O
specifying	O
a	O
username	O
and	O
password	O
may	O
be	O
found	O
in	O
the	O
browsers	B-Application
 '	O
documentation	O
(	O
e.g.	O
,	O
Firefox	B-Application
and	O
Internet	B-Application
Explorer	I-Application
)	O
.	O
</s>
<s>
By	O
default	O
,	O
most	O
web	B-Application
browsers	I-Application
use	O
passive	O
(	O
PASV	O
)	O
mode	O
,	O
which	O
more	O
easily	O
traverses	O
end-user	O
firewalls	B-Application
.	O
</s>
<s>
Some	O
variation	O
has	O
existed	O
in	O
how	O
different	O
browsers	B-Application
treat	O
path	O
resolution	O
in	O
cases	O
where	O
there	O
is	O
a	O
non-root	O
home	O
directory	O
for	O
a	O
user	O
.	O
</s>
<s>
Most	O
common	O
download	B-Protocol
managers	I-Protocol
can	O
receive	O
files	O
hosted	O
on	O
FTP	B-Protocol
servers	I-Protocol
,	O
while	O
some	O
of	O
them	O
also	O
give	O
the	O
interface	O
to	O
retrieve	O
the	O
files	O
hosted	O
on	O
FTP	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
DownloadStudio	B-Protocol
allows	O
not	O
only	O
download	O
a	O
file	O
from	O
FTP	B-Protocol
server	I-Protocol
but	O
also	O
view	O
the	O
list	O
of	O
files	O
on	O
a	O
FTP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
LibreOffice	B-Application
supports	O
opening	O
file	O
from	O
FTP	B-Protocol
servers	I-Protocol
,	O
but	O
from	O
7.4	O
release	O
,	O
this	O
feature	O
is	O
labeled	O
deprecated	O
,	O
and	O
developers	O
intend	O
to	O
remove	O
it	O
in	O
a	O
future	O
version	O
.	O
</s>
<s>
FTP	B-Protocol
was	O
not	O
designed	O
to	O
be	O
a	O
secure	O
protocol	O
,	O
and	O
has	O
many	O
security	O
weaknesses	O
.	O
</s>
<s>
FTP	B-Protocol
does	O
not	O
encrypt	O
its	O
traffic	O
;	O
all	O
transmissions	O
are	O
in	O
clear	O
text	O
,	O
and	O
usernames	O
,	O
passwords	O
,	O
commands	O
and	O
data	O
can	O
be	O
read	O
by	O
anyone	O
able	O
to	O
perform	O
packet	B-Protocol
capture	I-Protocol
(	O
sniffing	B-Protocol
)	O
on	O
the	O
network	O
.	O
</s>
<s>
This	O
problem	O
is	O
common	O
to	O
many	O
of	O
the	O
Internet	O
Protocol	O
specifications	O
(	O
such	O
as	O
SMTP	B-Protocol
,	O
Telnet	B-Protocol
,	O
POP	B-Protocol
and	O
IMAP	B-Protocol
)	O
that	O
were	O
designed	O
prior	O
to	O
the	O
creation	O
of	O
encryption	O
mechanisms	O
such	O
as	O
TLS	B-Protocol
or	O
SSL	O
.	O
</s>
<s>
Using	O
the	O
secure	O
versions	O
of	O
the	O
insecure	O
protocols	O
,	O
e.g.	O
,	O
FTPS	B-Protocol
instead	O
of	O
FTP	B-Protocol
and	O
TelnetS	B-Protocol
instead	O
of	O
Telnet	B-Protocol
.	O
</s>
<s>
SSH	B-Protocol
File	I-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
or	O
Secure	B-Protocol
Copy	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Using	O
a	O
secure	O
tunnel	O
such	O
as	O
Secure	B-Protocol
Shell	I-Protocol
(	O
SSH	B-Protocol
)	O
or	O
virtual	B-Application
private	I-Application
network	I-Application
(	O
VPN	B-Application
)	O
.	O
</s>
<s>
FTP	B-Protocol
over	O
SSH	B-Protocol
is	O
the	O
practice	O
of	O
tunneling	O
a	O
normal	O
FTP	B-Protocol
session	O
over	O
a	O
Secure	B-Protocol
Shell	I-Protocol
connection	O
.	O
</s>
<s>
Because	O
FTP	B-Protocol
uses	O
multiple	O
TCP	B-Protocol
connections	O
(	O
unusual	O
for	O
a	O
TCP/IP	B-Protocol
protocol	I-Protocol
that	O
is	O
still	O
in	O
use	O
)	O
,	O
it	O
is	O
particularly	O
difficult	O
to	O
tunnel	O
over	O
SSH	B-Protocol
.	O
</s>
<s>
With	O
many	O
SSH	B-Protocol
clients	O
,	O
attempting	O
to	O
set	O
up	O
a	O
tunnel	O
for	O
the	O
control	O
channel	O
(	O
the	O
initial	O
client-to-server	O
connection	O
on	O
port	B-Protocol
21	I-Protocol
)	O
will	O
protect	O
only	O
that	O
channel	O
;	O
when	O
data	O
is	O
transferred	O
,	O
the	O
FTP	B-Protocol
software	O
at	O
either	O
end	O
sets	O
up	O
new	O
TCP	B-Protocol
connections	O
(	O
data	O
channels	O
)	O
and	O
thus	O
have	O
no	O
confidentiality	O
or	O
integrity	O
protection	O
.	O
</s>
<s>
Otherwise	O
,	O
it	O
is	O
necessary	O
for	O
the	O
SSH	B-Protocol
client	B-Protocol
software	I-Protocol
to	O
have	O
specific	O
knowledge	O
of	O
the	O
FTP	B-Protocol
protocol	I-Protocol
,	O
to	O
monitor	O
and	O
rewrite	O
FTP	B-Protocol
control	O
channel	O
messages	O
and	O
autonomously	O
open	O
new	O
packet	B-Protocol
forwardings	I-Protocol
for	O
FTP	B-Protocol
data	O
channels	O
.	O
</s>
<s>
Explicit	O
FTPS	B-Protocol
is	O
an	O
extension	O
to	O
the	O
FTP	B-Protocol
standard	O
that	O
allows	O
clients	O
to	O
request	O
FTP	B-Protocol
sessions	O
to	O
be	O
encrypted	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
sending	O
the	O
"	O
AUTH	O
TLS	B-Protocol
"	O
command	O
.	O
</s>
<s>
The	O
server	B-Application
has	O
the	O
option	O
of	O
allowing	O
or	O
denying	O
connections	O
that	O
do	O
not	O
request	O
TLS	B-Protocol
.	O
</s>
<s>
Implicit	O
FTPS	B-Protocol
is	O
an	O
outdated	O
standard	O
for	O
FTP	B-Protocol
that	O
required	O
the	O
use	O
of	O
a	O
SSL	O
or	O
TLS	B-Protocol
connection	O
.	O
</s>
<s>
It	O
was	O
specified	O
to	O
use	O
different	O
ports	O
than	O
plain	O
FTP	B-Protocol
.	O
</s>
<s>
The	O
SSH	B-Protocol
file	I-Protocol
transfer	I-Protocol
protocol	I-Protocol
(	O
chronologically	O
the	O
second	O
of	O
the	O
two	O
protocols	O
abbreviated	O
SFTP	O
)	O
transfers	O
files	O
and	O
has	O
a	O
similar	O
command	O
set	O
for	O
users	O
,	O
but	O
uses	O
the	O
Secure	B-Protocol
Shell	I-Protocol
protocol	I-Protocol
(	O
SSH	B-Protocol
)	O
to	O
transfer	O
files	O
.	O
</s>
<s>
Unlike	O
FTP	B-Protocol
,	O
it	O
encrypts	O
both	O
commands	O
and	O
data	O
,	O
preventing	O
passwords	O
and	O
sensitive	O
information	O
from	O
being	O
transmitted	O
openly	O
over	O
the	O
network	O
.	O
</s>
<s>
It	O
cannot	O
interoperate	O
with	O
FTP	B-Protocol
software	O
,	O
though	O
some	O
FTP	B-Protocol
client	I-Protocol
software	O
offers	O
support	O
for	O
the	O
SSH	B-Protocol
file	I-Protocol
transfer	I-Protocol
protocol	I-Protocol
as	O
well	O
.	O
</s>
<s>
Trivial	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
TFTP	O
)	O
is	O
a	O
simple	O
,	O
lock-step	O
FTP	B-Protocol
that	O
allows	O
a	O
client	B-Protocol
to	O
get	O
a	O
file	O
from	O
or	O
put	O
a	O
file	O
onto	O
a	O
remote	O
host	O
.	O
</s>
<s>
One	O
of	O
its	O
primary	O
uses	O
is	O
in	O
the	O
early	O
stages	O
of	O
booting	B-Device
from	I-Device
a	I-Device
local	I-Device
area	I-Device
network	I-Device
,	O
because	O
TFTP	O
is	O
very	O
simple	O
to	O
implement	O
.	O
</s>
<s>
TFTP	O
lacks	O
security	O
and	O
most	O
of	O
the	O
advanced	O
features	O
offered	O
by	O
more	O
robust	O
file	B-Protocol
transfer	I-Protocol
protocols	I-Protocol
such	O
as	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Simple	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
the	O
first	O
protocol	O
abbreviated	O
SFTP	O
)	O
,	O
as	O
defined	O
by	O
,	O
was	O
proposed	O
as	O
an	O
(	O
unsecured	O
)	O
file	B-Protocol
transfer	I-Protocol
protocol	I-Protocol
with	O
a	O
level	O
of	O
complexity	O
intermediate	O
between	O
TFTP	O
and	O
FTP	B-Protocol
.	O
</s>
<s>
It	O
has	O
a	O
command	O
set	O
of	O
11	O
commands	O
and	O
support	O
three	O
types	O
of	O
data	O
transmission	O
:	O
ASCII	B-Protocol
,	O
binary	O
and	O
continuous	O
.	O
</s>
<s>
Below	O
is	O
a	O
summary	O
of	O
FTP	B-Protocol
reply	I-Protocol
codes	I-Protocol
that	O
may	O
be	O
returned	O
by	O
an	O
FTP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
These	O
replies	O
relay	O
status	O
codes	O
from	O
the	O
server	B-Application
file	O
system	O
.	O
</s>
