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    Port 20 blocked

    This is a discussion on Port 20 blocked within the Sky Router forums, part of the Sky Broadband help category; Anyone else have Port 20 blocked? Open Port Check Tool gives the following: Error: I could not see your service ...

    1. #1
      mville's Avatar
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      Port 20 blocked

      Anyone else have Port 20 blocked?

      Open Port Check Tool gives the following:

      Error: I could not see your service on xx.xxx.xx.xxx on port (20)
      Reason: Connection refused

      and I am unable to access my own ftp site externally, thru the NETGEAR DG834GT router, although the ftp site works perfectly on my internal network.

      Any ideas? Thanks.

      mville
      Last edited by mville; 17-08-07 at 01:49 PM.


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    3. #2
      dflour69's Avatar
      dflour69 is offline Sky User Member
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      Re: Port 20 blocked

      Report from Home of Gibson Research Corporation

      "GRC Port Authority Report created on UTC: 2007-08-17 at 16:28:49

      Results from probe of port: 20

      0 Ports Open
      0 Ports Closed
      1 Ports Stealth
      ---------------------
      1 Ports Tested

      THE PORT tested was found to be: STEALTH.

      TruStealth: PASSED - ALL tested ports were STEALTH,
      - NO unsolicited packets were received,
      - NO Ping reply (ICMP Echo) was received."


      So mine is not closed.

    4. #3
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      Re: Port 20 blocked

      If you are looking to be able to get to your PC ftp server from the outside world you will need to add a rule in the firewall on the router to forward port 20 traffic to your pc.

      Login to your router via 192.168.0.1 or NETGEAR Support Home Page and select firewall rules. You will need one for port 20 and possibly port 21 pointing to the LAN ip address of your ftp server.

      Is worth giving your pc with ftp on a fixed ip address, or use dhcp on the router to make a reservation so it gets the same address each time.

      Hope this helps.

      HC

    5. #4
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      Re: Port 20 blocked

      I've created a firewall rule, for port 20 and 21 to my LAN pc, but I get a Connection Refused error.

      mville

    6. #5
      mezzarelli's Avatar
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      Exclamation Re: Port 20 blocked

      Yes please if anyone out there has had the same problem and has fixed it, please help!

      i have setup remote desktop, all works fine..i then needed to setup an FTP site, finally thought i was getting somewhere but i get 'connection closed by remote host'..

      i have forwarded port 20 to my pc, ftp is allowed through my firewall..so why is port 20 still blocked>?

      in fact i have tried all ports open and used open port check Open Port Check Tool and 21 is open and 20 is blocked...

      i am pulling my hair out! please help me

    7. #6
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      Re: Port 20 blocked

      Hi

      Your FTP is working

      You have a Hello Txt file there

      I just checked your IP and connected no problems.


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    8. #7
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      Re: Port 20 blocked

      ummm, but i can only see that when i use ftp://localhost etc.. not when i try the IP address or my dynamic dns name.... how come you can see my test file.. i'm even more confused now...

    9. #8
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      Re: Port 20 blocked

      Because you cannot access your external IP through NAT.


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    10. #9
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      Re: Port 20 blocked

      Hello everyone!
      I was fighting with same issue 2 nights :/ The real remedy was this topic and dflour69's post (man, thank to you ).
      Port is STEALTH so it doesn't answer to ping, so you cannot check it with tool like canUCme.org as ping will never return.
      There's no issue when loopbacking which makes it even more mysterious.

      I have VirtualServers (redirecting) set in my router for both ports 20 and 21, both are open in firewall and firewall-like soft from Xp, I've also set Triggering for 20 just in case (Active mode).
      I was trying to connect to my ftp from host from outside (my bro's computer which doesn't belong to network under my router - moreover he connects through another ISP). We were testing ftp using FF browser.

      As soon as I read this thread we changed to standalone ftp client and it worked!. Correct me if I'm wrong but the problem was that Firefox doesn't see port 20 in stealth mode, while ftp didn't care about it.
      But not everything is fine 'cause I'm not happy to install ftp client wherever I want to connect from.
      Anyone knows what is the source of problem (WinXP or my noble Internet Service Provider)?
      And how to change it (make port 20 open).
      Thanks!

    11. #10
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      Re: Port 20 blocked

      Firefox will always use passive FTP which is sometimes difficult to set up behind a NAT firewall. Essentially, the requesting computer will make a connection to port 21, say that it wants to use passive FTP, and then say what file or directory listing it wants to fetch. The FTP server then says, "OK, connect to port x to collect the data", where x is some arbitrary number between 1024 and 65534. The requesting computer then tries to connect to port x and download the file data or directory listing.

      When operating in active mode (such as when the requesting computer is using the command line ftp program), it makes a connection to port 21, says it wants to use active mode and that the incoming data be sent on port x, then requests the file. The ftp server then makes an outgoing connection to port x and transfers the data.

      To get things working for active FTP, all you need to do is forward port 21 to the PC with the FTP server. Because the data connection on "arbitrary port x" is outgoing, the router has no problem with it.

      Things are a bit more tricky if you want to support passive FTP though, because the data connection on arbitrary port x is incoming, so you don't know which port to need to forward, and in any case, it changes for every incoming request. NAT software on routers will sometimes have a special, "ftp aware" mechanism to handle incoming passive FTP requests. You may need to specifically select the FTP service in the firewall configuration on the router, rather than specifying port 21 by hand - I'm not sure.

      But the crucial thing is that you can't have a firewall running on your PC because that will just block the incoming connection on "arbitrary port x" that picks up the data.

      The stuff about port 20, by the way, is a bit of a red herring. Port 20 is the source port used for the outgoing data connections for active FTP. Enabling port forwarding for port 20 when you're trying to set up an FTP server is just meaningless really.

      So, try disabling the firewall on your PC and see if that works. If it does, then the NAT software on the router is clever enough to understand passive FTP. If it still doesn't work, then you'll need to configure your FTP server to use a specific range of passive ports (choose a range of numbers from within the 49152 to 65534 range - give it a range of at least a hundred or so), and then on the router, forward all those ports to the PC. It sounds drastic, but that's what you have to do to get passive FTP working.

     

     

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