FTP Protocol Details

1
FTP Protocol Details
Tips for the assignment
2
Socket Programming using TCP

• Socket a door between application process and
  end-end-transport protocol (UDP or TCP)
• TCP service reliable transfer of bytes from one
  process to another

3
Simple TCP Server-TCP Client
4
Client Sockets Server Sockets
5
Client/server socket interaction TCP
Server (running on hostid)
Client
Application 2-5
6
Simple Server Pseudo-Code

• socket
• bind
• listen
• loop "forever"
• accept / by creating new socket /
• / process the clients request /
• loop until done
• receive/send
• closesocket(newsocket)

7
Simple Client Pseudo-Code

• socket
• connect
• / process the clients request /
• loop until done
• send/receive
• closesocket(socket)

8
Proper Ordering of Send and Recv

• socket
• bind
• listen
• loop "forever"
• accept / by creating new socket /
• / process the clients request /
• loop until done
• receive/send
• closesocket(newsocket)

socket connect / process the clients request
/ loop until done send/receive closesocke
t(socket)
9
Test the TCP Client-Server Codes

• Run ServerWindows.c
• Compile ClientWindows.c, look for the executable.
• Run ClientWindows.c from the command prompt to
  connect to the server
• ClientWindows localhost 1234
• Alternatively, use IpConfig to find out what your
  IP address is (e.g. 130.123.123.111), then
  connect to the server using
• ClientWindows 130.123.123.111 1234
• Lets see how to use the compilers debug mode to
  trace the exchange of messages.

10
FTP Server
11
FTP (Multiple Clients)
C
TCP Control Socket
DIR
Port 127,0,0,1,6,11
Listening Socket
After file transfer
TCP Control Socket
Quit
S
TCP Active Data Socket
Server

• In TCP, the Server should be running already
  prior to a Client connecting to it

12
FTP Operation
13
FTP Operation
Note that Ports 1216 1217 are ephemeral ports.
Any port 1024, 65535 will work.
Source Computer Networking and the Internet
(5/e) by Fred Halsall
14
FTP Commands
COMMAND DESCRIPTION
USER username User name on the FTP server
PASS password Users password on the FTP server
SYST Type of operating system requested
TYPE type File type to be transferred A (ASCII), I (Image/Binary)
PORT n1,n2,n3,n4,n5,n6 Client IP address (n1-n4) and port number (n5, n6)
RETR filename.type Retrieve (get) a file
STOR filename.type Store (put) a file
LIST filelist List files or directories
QUIT Log off from server
Source Computer Networking and the Internet
(5/e) by Fred Halsall
15
FTP Reply Codes
REPLY DESCRIPTION
1yz Positive reply, wait for another reply before sending a new command
2yz Positive reply, a new command can be sent
3yz Positive reply, another command is awaited
4yz Negative reply, try again
5yz Negative reply, do not retry
x0z Syntax
x1z Information
x2z Control or data connection
x3z Authentication
x4z Unspecified
x5z File status
Source Computer Networking and the Internet
(5/e) by Fred Halsall
16
Active FTP (or Standard )
Standard (or PORT or Active) The Standard mode
FTP client sends PORT commands to the FTP server.
These commands are sent over the FTP command
channel when establishing the FTP
session. Operation Standard mode FTP clients
first establish a connection to TCP port 21 on
the FTP server. This connection establishes the
FTP command channel. The client sends a PORT
command over the FTP command channel when the FTP
client needs to send or receive data, such as a
folder list or file. The PORT command contains
information about which port the FTP client
receives the data connection on. In Standard
mode, the FTP server always starts the data
connection from TCP port 20. The FTP server must
open a new connection to the client when it sends
or receives data, and the FTP client requests
this by using the PORT command again.
17
Passive FTP (or PASV)
Passive (or PASV) The Passive mode client sends
PASV commands to the FTP Server. Operation Passiv
e mode FTP clients also start by establishing a
connection to TCP port 21 on the FTP server to
create the control channel. When the client sends
a PASV command over the command channel, the FTP
server opens an ephemeral port (between 1024 and
5000) and informs the FTP client to connect to
that port before requesting data transfer. As in
Standard mode, the FTP client must send a new
PASV command prior to each new transfer, and the
FTP server will await a connection at a new port
for each transfer.
18
Active FTP mode
p. 50, RFC 959
19
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Passive open
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
20
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
21
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
22
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
23
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
24
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
25
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
26
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
27
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
SYST
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
28
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
SYST
215 UNIX TypeX VersionY
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
29
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
get ltfilename.typegt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
30
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
31
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
32
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
RETR ltfilename.typegt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
33
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
RETR ltfilename.typegt
150 opening ASCII mode data connection
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
34
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
Server does an active open to Port n5, n6
RETR ltfilename.typegt
150 opening ASCII mode data connection
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
35
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
Server does an active open to Port n5, n6
RETR ltfilename.typegt
150 opening ASCII mode data connection
Send file through data connection
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
36
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
Server does an active open to Port n5, n6
RETR ltfilename.typegt
150 opening ASCII mode data connection
Send file through data connection
226 File transfer complete
User prompted for a conmand
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
37
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
Server does an active open to Port n5, n6
RETR ltfilename.typegt
150 opening ASCII mode data connection
Send file through data connection
226 File transfer complete
QUIT
User prompted for a conmand
Source Computer Networking and the Internet
(5/e) by Fred Halsall
38
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
Server does an active open to Port n5, n6
RETR ltfilename.typegt
150 opening ASCII mode data connection
Send file through data connection
226 File transfer complete,
QUIT
User prompted for a conmand
221 Goodbye
Source Computer Networking and the Internet
(5/e) by Fred Halsall
39
ACTIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 20
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PORT n1-n6
get ltfilename.typegt
200 PORT command successful
Server does an active open to Port n5, n6
RETR ltfilename.typegt
150 opening ASCII mode data connection
Send file through data connection
226 File transfer complete,
QUIT
User prompted for a conmand
Server closes data connection first , then
control connection
221 Goodbye
Source Computer Networking and the Internet
(5/e) by Fred Halsall
40
Passive FTP mode
41
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Passive open
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
42
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
43
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
44
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
45
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
46
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
47
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
48
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
49
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
SYST
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
50
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
SYST
215 UNIX TypeX VersionY
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
51
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
220 user ltusernamegt logged in
PASV
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
52
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port 2024
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
53
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port 2024
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
dir
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
54
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port 2024
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
55
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port 2024
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
56
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port n5, n6 (or Port 2024 in this example)
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
Client does an active open to Port n5,n6
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
57
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port n5, n6 (or Port 2024 in this example)
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
Client does an active open to Port n5,n6
Send file through data connection
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
58
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port n5, n6 (or Port 2024 in this example)
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
Client does an active open to Port n5,n6
Send file through data connection
226 File transfer complete
User is prompted for a command
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
59
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port n5, n6 (or Port 2024 in this example)
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
Client does an active open to Port n5,n6
Send file through data connection
226 File transfer complete
QUIT
User is prompted for a command
time
Source Computer Networking and the Internet
(5/e) by Fred Halsall
60
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port n5, n6 (or Port 2024 in this example)
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
Client does an active open to Port n5,n6
Send file through data connection
226 File transfer complete
QUIT
User is prompted for a command
time
221 Goodbye
Source Computer Networking and the Internet
(5/e) by Fred Halsall
61
PASSIVE FTP Operation
CLIENT
SERVER
Data connection
control connection
Data connection
control connection
Port 2024
Port 21
Port 1120
Port 1121
Active open
Passive open
TCP control connection to Port 21 established
220 FTP server ready
USER ltusernamegt
331 password required
PASS ltpasswordgt
Port n5, n6 (or Port 2024 in this example)
220 user ltusernamegt logged in
PASV
227 Entering PASV mode (192,168,150,90,195,149)
LIST
dir
150 Opening ASCII mode data connection for file
list
Client does an active open to Port n5,n6
Send file through data connection
226 File transfer complete
QUIT
User is prompted for a command
Server closes data connection first , then
control connection
time
221 Goodbye
Source Computer Networking and the Internet
(5/e) by Fred Halsall
62
ACTIVE FTP Operation
CLIENT
SERVER
Source Computer Networking and the Internet
(5/e) by Fred Halsall
63
Security Issues
Firewall administrators may not want to use
Passive mode FTP servers because the FTP server
can open any ephemeral port number. Many FTP
servers are configured with an ephemeral port
range of 1024 through 65535. Firewall
configurations that allow full access to all
ephemeral ports for unsolicited connections may
be considered unsecured.
http//support.microsoft.com/kb/323446
64
Some utility Netstat
COMMAND Netstat -a
Active Connections Proto Local Address
Foreign Address
State TCP IT027049http
IT027049.massey.ac.nz0 LISTENING TCP
IT027049epmap IT027049.massey.ac.nz0
LISTENING TCP IT027049https
IT027049.massey.ac.nz0 LISTENING TCP
IT027049microsoft-ds IT027049.massey.ac.nz0
LISTENING TCP IT0270491025
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491179 IT027049.massey.ac.nz0
LISTENING TCP IT0270491181
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491300 IT027049.massey.ac.nz0
LISTENING TCP IT0270491318
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491786 IT027049.massey.ac.nz0
LISTENING TCP IT0270491787
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491790 IT027049.massey.ac.nz0
LISTENING TCP IT0270491791
IT027049.massey.ac.nz0 LISTENING TCP
IT0270495000 IT027049.massey.ac.nz0
LISTENING TCP IT02704913450
IT027049.massey.ac.nz0 LISTENING TCP
IT027049netbios-ssn IT027049.massey.ac.nz0
LISTENING TCP IT0270491082
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491179 its-xchg4.massey.ac.nz1165
ESTABLISHED TCP IT0270491181
its-dc2.massey.ac.nz1025 ESTABLISHED TCP
IT0270491318 hnt-up-dhcp-494.wharton.upe
nn.edu62686 ESTABLISHED TCP IT0270491456
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491456 alb-file2.massey.ac.nzne
tbios-ssn ESTABLISHED TCP IT0270491467
IT027049.massey.ac.nz0 LISTENING TCP
IT0270491467 itsa-campus1.massey.ac.nzn
etbios-ssn ESTABLISHED TCP IT0270491786
d226-94-36.home.cgocable.net7091
ESTABLISHED
Displays all active TCP connections and the TCP
and UDP ports on which the computer is listening
65
TCP IT0270491787 pcp0011009611pcs.de
trtc01.mi.comcast.net21848 ESTABLISHED TCP
IT0270491790 balticom-132-227.balticom.l
v63567 ESTABLISHED TCP IT0270491791
24-29-117-20.nyc.rr.com1236 ESTABLISHED TCP
IT0270498947 IT027049.massey.ac.nz0
LISTENING UDP IT027049microsoft-ds
UDP IT027049isakmp
UDP IT0270491026
UDP
IT0270491027
UDP IT0270491028
UDP IT0270491046
UDP IT0270491088
UDP IT0270491177
UDP IT02704913450
UDP
IT02704938037
UDP IT027049ntp
UDP IT0270491187
UDP IT0270491459
UDP IT0270491718
UDP IT0270491900
UDP
IT027049ntp
UDP IT027049netbios-ns
UDP IT027049netbios-dgm
UDP IT0270491900
UDP IT0270498760
UDP IT02704962493

66
How to change the Internet Explorer FTP Client
mode

• Start Internet Explorer.
• On the Tools menu, click Internet Options.
• Click the Advanced tab.
• Under Browsing, click to clear the Enable folder
  view for FTP sites check box.
• Click to select the Use Passive FTP (for firewall
  and DSL modem compatibility) check box.
• Internet Explorer behaves as a Standard mode
  FTP client if you select the Enable folder view
  for FTP sites check box, even if you also select
  the Use Passive FTP check box. If you clear the
  Enable folder view for FTP sites check box and
  then select the Use Passive FTP check box,
  Internet Explorer behaves as a Passive mode FTP
  client.

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The End