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Port 21 is forced closed?

Phil Norris
Occasional Advisor

Port 21 is forced closed?

Using www.grc.com for testing it.

Got a LinkSys router. BEFRS41.

Even if I set it to a DMZ Host it still registers Port 21 as being blocked.

Thus when I try to ftp to our work servers it ups 8k then says its complete.

Doubtful it's router-side if it's still blocked under DMZ.

And the WindowsXP firewall is off.
11 REPLIES
Ron Kinner
Honored Contributor

Re: Port 21 is forced closed?

FTP is really two ports and you have to be careful not to confuse the server with the client. Port 21 is used by the server to accept logins and requests. The connection is made from a random port on the client to the server. Once logged in, if you request a data transfer, it will open a second connection. By default this is from port 20 on the server back to the client's 1 + source port used to establish the port 21 connection. This gets blocked by almost all firewalls so ftp has a workaround called passive mode.

In passive mode the connection is made from the client back to port 20 on the server and this can be passed by a firewall. In Internet Explorer you tell it to use Passive mode via Tools/Internet Options/Advanced then check Use Passive FTP. As your ISP may be doing some firewalling this is a good way to go and may fix your problem which I gather is really not being able to upload to an FTP server. You may have better luck with one of the stand alone ftp clients such as winftp
http://www.softtechdesign.com/products/WinFTP/winftp.htm
They have a free demo but the real program costs $20. There are lots of free ftp clients around. See:

http://freeware.intrastar.net/ftp.htm

Many problems like yours are caused by not using the correct login or password or not going to the correct directory once logged in. This is much more visible on the stand alone programs. Your space on the server may be limited to a very small size so make sure you have not used up all of your space.

Just because you can FTP out does not mean you can FTP in. You have to have an FTP server running and listening on port 21.

netstat -an

will show you if you have an FTP server running. Normally there is not one running by default. IF you need one (and I really doubt you do) get the best(War FTP Daemon) at

http://support.jgaa.com/index.php?cmd=ShowProduct&ID=1

and the www.grc should see port 21 open.

Ron
Phil Norris
Occasional Advisor

Re: Port 21 is forced closed?

Well that straightens that up. Guess I don't have to worry about any ports for going out from the computer.

Still have the incomplete file thing though. I've been reading that it appears to be a common MTU issue with regards to these routers. Have yet to find a solution though.
seymour999
Frequent Advisor

Re: Port 21 is forced closed?

What is the Linksys MTU set to now?
Phil Norris
Occasional Advisor

Re: Port 21 is forced closed?

Originally 1492. I've tried numerous settings on it though.
Ron Kinner
Honored Contributor

Re: Port 21 is forced closed?

What ftp client are you trying to use?

Did you try one of the freeware clients yet?

Ron
Phil Norris
Occasional Advisor

Re: Port 21 is forced closed?

ok. Got a hold of a different brand of router and same problem. Got an ftp client on the other system and no problem with uploading.

So it's this computer. What could it be? ha.

Reinstalled XP and did nothing.

Tried SmartFTP and Bulletproof and nothing.
Ron Kinner
Honored Contributor

Re: Port 21 is forced closed?

Could be a duplex mismatch between the PC and the router. If one is full and the other is half that can cause so many errors that the connection is unusable during high transfers but works OK for small files or when transfering in the other direction. Are you able to download ftp files?

What PC and what NIC are you using? Some of the NICs have some statistics that will help diagnose the problem.

Ron
Phil Norris
Occasional Advisor

Re: Port 21 is forced closed?

Have a 3Com Gigabit 3C490 onboard.

It's a P4 2.6C, 512 Dual Channel, etc.

ASUS P4P800 with this NIC onboard.

I can download no problem at all. And I can fxp between work servers no problem. Just can't upload more than 8192 bytes.



Ron Kinner
Honored Contributor

Re: Port 21 is forced closed?

OK. I suspect you have a 3C940 rather than a 490 but it doesn't matter. You should have the 3COM diagnostics anyway. Right Click on My Network Places and Select Properties. Then right click on Local Area Connection and select Properties. Now select Configure and then Statistics. Do you see any errors or collisions? Run the Diagnostics under the other tab. See if they see anything. Then look under configuration and tell me what duplex and media-type it thinks it sees.

Do you have the latest driver from asus?

3Com Gigabit LOM (3C940) Driver V1.00.00.0046 for Windows

http://www.asus.com/support/download/item.aspx?ModelName=P4P800%20Deluxe


Ron
Phil Norris
Occasional Advisor

Re: Port 21 is forced closed?

Yes sorry its the 940.

No I didn't have the latest. I had .44. Thought I had the latest. I'm getting those and trying the things now.
Phil Norris
Occasional Advisor

Re: Port 21 is forced closed?

Ok. Got those latest .46 now. It still does it. Slightly differently. More of a pause before it does it. What it does is assume it's 100% complete and shows that but shows it transfering at 2,016k/s. As much as I wish that was my upload it's not.

And on a 5 meg file say it'll get 750k or so of it and then say it's finished.

It says the diagnostics aren't installed on this computer. I assumed it came with the latest drivers but I guess not. I've also not found them on the 3Com site or the Asus site.