Nmap not picking up port
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Thread: Nmap not picking up port

  1. #1
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    Nmap not picking up port

    Just curious about this. The output of the netstat -ta command shows two listening ports:

    Active Internet connections (servers and established)
    Proto Recv-Q Send-Q Local Address Foreign Address State
    tcp 0 0 localhost.localdomain:ipp *:* LISTEN
    tcp 0 0 localhost.localdomain:5335 *:* LISTEN

    ipp is the CUPS server on port 631 tcp
    the second entry is the MdnsResponder service listening on port 5335

    When I run Nmap to scan myself, it shows CUPS listening on 631 ok, but it doesn't show 5335 as open. I was thinking that if a service was listening on a port then, then the port is open. Why doesn't Nmap pick up this port as "open"?

    Edit: I am just using the "connect" scan option with Nmap.
    For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
    (Romans 6:23, WEB)

  2. #2
    Dissident 4dm1n brokencrow's Avatar
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    I've used nmap quite a bit and have noted it only scans 1662 ports by default. The -p switch will let you scan a fuller range of ports.
    “Everybody is ignorant, only on different subjects.” — Will Rogers

  3. #3
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    I've used nmap quite a bit and have noted it only scans 1662 ports by default. The -p switch will let you scan a fuller range of ports.

    You know, as many times as I have used Nmap to scan myself and have seen the "of the 1662 ports (or whatever it has been in the version I've used)" it has not dawned on me that it was not scanning all my ports. I was assuming that it scanned them all by default, and so I ignored a plain message to the contrary. Thanks for furthering my education.
    For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
    (Romans 6:23, WEB)

  4. #4
    Dissident 4dm1n brokencrow's Avatar
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    It seems the default amount of scanned ports varies with nmap. The Windows version scans 1662. Nmap 3.81 running on Ubuntu only scans 1644. Fwiw.
    “Everybody is ignorant, only on different subjects.” — Will Rogers

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