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Thread: Closed ports problem

  1. #1
    Join Date
    Mar 2010
    Beans
    2

    Closed ports problem

    Hi all,

    I have just built my home server from fresh, using Kubuntu 64 bit. I can access my server from both LAN and WAN for web (port 80) and ssh (port 22) services as well as ping it.

    However, I can't access my server for ftp (port 21 - using proftpd) and Motion webcam server (port 8081) from both LAN and WAN.

    A port forwarding web site told me that ports 21 and 8081 on my server are still closed but I don't know why because I have programs running and listening, the firewall seems not to block them:

    nmap localhost:

    21/tcp open ftp
    22/tcp open ssh
    25/tcp open smtp
    80/tcp open http
    143/tcp open imap
    631/tcp open ipp
    993/tcp open imaps
    3306/tcp open mysql
    8080/tcp open http-proxy
    8081/tcp open blackice-icecap

    iptables -L -n:
    ...
    Chain ufw-user-input (1 references)
    target prot opt source destination
    ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:21
    ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:21
    ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8081
    ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:8081
    ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080
    ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:8080
    ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:20
    ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:20

    I can do ftp itself (ftp localhost) as well as access to webcam server locally (using http://localhost:8081).

    I have checked router's configure carefully (perhaps it is correctly set). BTW, I can't access from other LAN computers either (I have also changed my ADSL router from Dynalink to Billion but situation is the same).

    I am stuck and don't know what to try nor what is the next step.

    Can someones help me? Thanks a lot in advance.

  2. #2
    Join Date
    Mar 2010
    Location
    Los Angeles, CA
    Beans
    231
    Distro
    Ubuntu 10.04 Lucid Lynx

    Re: Closed ports problem

    It's a firewall issue. Not sure which one, but it's a firewall issue.

    Can you nmap the box from itself targeting its private IP (NOT localhost) and get the same results? If so, what does nmaping the box from another LAN machine return?
    Postfix problems? Come find me in #postfix on the freenode IRC network.

  3. #3
    Join Date
    Nov 2007
    Location
    Newry, Northern Ireland
    Beans
    1,192

    Re: Closed ports problem

    You may need to specify that the rules apply to your ethernet connection as well as to the lo (Local Loopback) connection I had a problem recently where things were not working as expected, because I had opened a port on the eth0 interface but not on the lo interface in the firewall rules.

    I also find the firewall easier to configure if I use the Webmin Interface.
    Can't think of anything profound or witty.
    My Blog: http://gonzothegeek.blogspot.co.uk/

  4. #4
    Join Date
    Mar 2010
    Location
    Los Angeles, CA
    Beans
    231
    Distro
    Ubuntu 10.04 Lucid Lynx

    Re: Closed ports problem

    Yeah, I hate webmin, but I'm also no wizard with iptables. I'm torn. :-/

    Just make sure that the rules aren't solely being applied to localhost; the lo interface is ONLY reachable from the machine itself.
    Postfix problems? Come find me in #postfix on the freenode IRC network.

  5. #5
    Join Date
    Mar 2010
    Beans
    2

    SOLVED: Closed ports problem

    Oops, my big mistake.

    After installing webmin, it shows me immediately that not only Linux firewall, but I have also other one: shorewall (installed when I was following a mail server installation tutor). I have removed it and now everything seems be under my control.

    BTW, webmin is very impressive to me. I may "hate" it later but not now

    Thank you all very much. I highly appreciate.
    Last edited by tonypham; March 27th, 2010 at 04:23 AM.

  6. #6
    Join Date
    Nov 2007
    Location
    Newry, Northern Ireland
    Beans
    1,192

    Re: Closed ports problem

    I have to admit that I sometimes love Webmin and sometimes hate it.

    As long as you don't use it to try and configure Virtual Hosts in Apache or some other things, it works well. Hit a module where it does not work the Debian way and you're in big trouble.

    For Firewalls it is much better that Ebox IMHO, much more intuitive, and that is pretty much all I use Webmin for, oh and for Samba administration and some MySQL stuff.
    Can't think of anything profound or witty.
    My Blog: http://gonzothegeek.blogspot.co.uk/

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