Question

How to Check Port 21 is Open

Asked by: allanau20

Hi Experts!

How do I check if port 21 is open on a specific box?

Tried: http://www.canyouseeme.org/

It's saying that it could not see the service connection refused and connetion timed out.

T I A !

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Asked On
2007-04-25 at 17:21:43ID22534786
Tags

port

,

check

,

open

,

how

,

21

Topics

FTP Servers

,

Windows Networking

,

Network Software Firewalls

Participating Experts
3
Points
500
Comments
18

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Answers

 

by: allanau20Posted on 2007-04-25 at 17:23:28ID: 18978542

I see port 21 on this file:

%SystemRoot%\system32\drivers\etc\services

# <service name>  <port number>/<protocol>  [aliases...]   [#<comment>]
ftp                                                      21/tcp                           #FTP. control

Does it mean it's open?
T I A

 

by: grsteedPosted on 2007-04-25 at 19:20:51ID: 18978946

At a command (CMD) prompt try NETSTAT -A

It will show you what port you system is listening on for TCP and UDP

Cheers,
Gary

 

by: ygouthamPosted on 2007-04-25 at 22:25:27ID: 18979398

you can always try a

telnet host.ip.address.here 21

######## OUTPUT ##########

Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 (vsFTPd 2.0.5)
HELO
530 Please login with USER and PASS.

###########################

that means the FTP daemon is listening on port 21

 

by: keith_alabasterPosted on 2007-04-25 at 23:39:13ID: 18979595

No, the services file just defines the service ports and provides a lookup for certain systems, it is nothing to do with whether a port is open or not.

Have you port-forwarded port 21 on your external router to the box concerned?
What is providing the FTP? IIS Server? Can you ftp to the box internally?

 

by: allanau20Posted on 2007-04-26 at 09:15:11ID: 18982773

Thanks Keith.
I don't have access to routers, just the box.
I'll ask System folks if "port-forwarded port 21 on the external router to the box".

>>What is providing the FTP?
I'm using WS FTP Pro.

>> Can you ftp to the box internally?
Yes, through DOS FTP.

Thanks again!

 

by: keith_alabasterPosted on 2007-04-26 at 10:20:38ID: 18983391

OK - wait for feedback that ftp is being allowed in from outside - the fact that you can connect to it internally shows port 21 must be open on the box.

Regards
Keith

 

by: allanau20Posted on 2007-04-26 at 10:39:59ID: 18983582

Sorry for the confusion Keith.

I"m able to DOS FTP from my box, but on another box where the app resides I'm not able to DOS FTP or Telnet with port 21. Does that mean it's not opened?

Thanks.

 

by: keith_alabasterPosted on 2007-04-26 at 10:44:26ID: 18983612

can you ftp to the system where the app is installed from your PC? If yes, the port is open on the app machine :)

 

by: allanau20Posted on 2007-04-26 at 10:48:14ID: 18983644

Thanks Keith.

Tried and got this msg:
>ftp: connect :Unknown error number

Tried to IP and the server name.

 

by: allanau20Posted on 2007-04-26 at 11:59:17ID: 18984213

Keith,

However, I was not able to FTP to my co-workers workstation, different from where the app is, and could not FTP or telnet with port 21. But on his box he's able to do a DOS FTP.
This does not mean that port 21 is closed on his workstation, right?
So, we don't know if port 21 is closed on where the app is, right?

Thanks for your help!

 

by: keith_alabasterPosted on 2007-04-26 at 12:13:25ID: 18984341

Yes, it is closed. Remember, port 21 is the destination port, not the source port for ftp. Therefore you can all ftp out to a system that is running an ftp service such as the app server. Dos ftp is an ftp client that could use any free port that it wants above 1024, it is not a server service that listens on port 21 (or whatever other port is may be using)

IIS for example provides an ftp service that listens on port 21. DOS ftp provides a client that you use to connect to an ftp service.

Assuming this is a windows 2000/2003 server that hosts the app or a windows xp machine (whatever) then netstat -a from a cmd prompt on any machine will tell you the position regarding ports open.

You will see a list produced that will give an ip address, a protocol, a port number and its state. If tou see tcp port 21 listed then that port is open.

Job done :)

 

by: allanau20Posted on 2007-04-26 at 14:39:36ID: 18985375

Hi Keith,

So I asked the network guy to check the router, and this was his reply:

I am looking at the Site2Site VPN router/Firewall Log, I don’t see ServerA(xx.xxx.xx.xx) being block.

Does this mean the router is not blocking it?

Thanks again for your help -- really apprciate it!

 

by: keith_alabasterPosted on 2007-04-26 at 15:08:07ID: 18985498

go to the machine you want to talk to on ftp.
at a cmd prompt, type in netstat -a.
Post the results here

 

by: allanau20Posted on 2007-04-26 at 16:29:38ID: 18985932

Thanks in advance for your help!

On the server that I want to run the WS FTP Pro app:

Microsoft Windows [Version 5.2.3790]
(C) Copyright 1985-2003 Microsoft Corp.

C:\>netstat -a

Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    ServerA:http          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:epmap         ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:microsoft-ds  ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:1040          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:1062          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:1095          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:1101          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:1311          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:ms-olap1      ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:ms-olap2      ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:msolap-ptp2   ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:3189          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:ms-wbt-server  ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:4215          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:5001          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:8000          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:8080          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:8081          ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:12162         ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:netbios-ssn   ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:1086          Server10079.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1101          ServerA.mydomain.com:1110  ESTABLISHED
  TCP    ServerA:1107          Server10244.mydomain.com:1162  ESTABLISHED
  TCP    ServerA:1110          ServerA.mydomain.com:1101  ESTABLISHED
  TCP    ServerA:1136          Server10003.mydomain.com:1025  ESTABLISHED
  TCP    ServerA:1140          Server10244.mydomain.com:1162  ESTABLISHED
  TCP    ServerA:1152          Server10004.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1200          Server10235.mydomain.com:epmap  ESTABLISHED
  TCP    ServerA:1201          Server10235.mydomain.com:1025  ESTABLISHED
  TCP    ServerA:1209          Server10004.mydomain.com:epmap  ESTABLISHED
  TCP    ServerA:1210          Server10004.mydomain.com:1025  ESTABLISHED
  TCP    ServerA:1214          Server10003.mydomain.com:ldap  TIME_WAIT
  TCP    ServerA:1216          Server10003.mydomain.com:ldap  TIME_WAIT
  TCP    ServerA:1217          Server10004.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1220          Server10004.mydomain.com:ldap  TIME_WAIT
  TCP    ServerA:1224          Server10076.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1227          Server10077.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1230          Server10078.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1233          Server10004.mydomain.com:epmap  ESTABLISHED
  TCP    ServerA:1234          Server10004.mydomain.com:1025  ESTABLISHED
  TCP    ServerA:1235          Server10004.mydomain.com:ldap  TIME_WAIT
  TCP    ServerA:1236          Server10004.mydomain.com:ldap  TIME_WAIT
  TCP    ServerA:1237          Server10136.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1241          Server10137.mydomain.com:microsoft-ds  ESTABLISHED

  TCP    ServerA:1243          Server11016.mydomain.com:netbios-ssn  TIME_WAIT
  TCP    ServerA:ms-wbt-server  dell-56hb2c1.mydomain.com:ms-olap2  ESTABLISHE
D
  TCP    ServerA:ms-wbt-server  dell-3zyjp21.mydomain.com:1252  ESTABLISHED
  TCP    ServerA:3640          Server10003.mydomain.com:1025  ESTABLISHED
  TCP    ServerA:3921          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3922          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3923          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3924          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3925          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3926          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3927          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3928          ServerA.mydomain.com:5001  ESTABLISHED
  TCP    ServerA:3933          EBAPPD04:microsoft-ds  ESTABLISHED
  TCP    ServerA:4524          Server11029.mydomain.com:ms-wbt-server  ESTABLISHE
D
  TCP    ServerA:5001          ServerA.mydomain.com:3921  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3922  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3923  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3924  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3925  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3926  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3927  ESTABLISHED
  TCP    ServerA:5001          ServerA.mydomain.com:3928  ESTABLISHED
  TCP    ServerA:ms-rule-engine  ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:11001         ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:11020         ServerA.mydomain.com:0  LISTENING
  TCP    ServerA:11021         ServerA.mydomain.com:0  LISTENING
  UDP    ServerA:snmp          *:*
  UDP    ServerA:microsoft-ds  *:*
  UDP    ServerA:isakmp        *:*
  UDP    ServerA:1025          *:*
  UDP    ServerA:1026          *:*
  UDP    ServerA:1104          *:*
  UDP    ServerA:1105          *:*
  UDP    ServerA:1137          *:*
  UDP    ServerA:1138          *:*
  UDP    ServerA:ms-sql-m      *:*
  UDP    ServerA:1964          *:*
  UDP    ServerA:ipsec-msft    *:*
  UDP    ServerA:4525          *:*
  UDP    ServerA:8081          *:*
  UDP    ServerA:8082          *:*
  UDP    ServerA:ntp           *:*
  UDP    ServerA:netbios-ns    *:*
  UDP    ServerA:netbios-dgm   *:*
  UDP    ServerA:ntp           *:*
  UDP    ServerA:1027          *:*
  UDP    ServerA:1057          *:*
  UDP    ServerA:1148          *:*
  UDP    ServerA:1170          *:*
  UDP    ServerA:1213          *:*
  UDP    ServerA:3630          *:*
  UDP    ServerA:4200          *:*
  UDP    ServerA:4494          *:*

C:>

 

by: keith_alabasterPosted on 2007-04-26 at 23:07:32ID: 18987013

There you go - no port 21 open. This shows that there is no ftp listening server service running/started.

The first line starts with TCP    ServerA:http          ServerA.mydomain.com:0  LISTENING

This shows port 80 (http) is open as the first entry (port 21 would have been above this if it was open)

 

by: allanau20Posted on 2007-04-27 at 12:20:49ID: 18991620

Thanks Keith.

My laptop does not show port 21 as you've mentioned when I did a netstat /a.
However, I was able to telnet VPN IP 21 <-- using port 21?
I know you said port 21 is receiving/destination (listening).
Even if I'm able to telnet using port 21, it doesn't mean it's open?

I know I'm a pain, but really appreciate your help!

 

by: keith_alabasterPosted on 2007-04-27 at 12:52:37ID: 18991780

I'm losing the thread of your question.

What is VPN IP?

 

by: allanau20Posted on 2007-04-27 at 12:54:44ID: 18991792

Sorry for the confusion.

I mean that the IP runs through a VPN connection, and the IP is the FTP Server outside of mydomain.com.

Thanks for your help.

20120131-EE-VQP-002

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