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Thread: Checking Ports

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    Checking Ports

    What's a good way to check if a given port is open or closed? Is there a tool I can use to check this on a Linux box?

    Thanks
    RalphF
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    Super Moderator Inigoesdr's Avatar
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    Ah, right, he wanted an online service - not a local test using his Linux box?

    In which case my personal fav is sheilds up: http://www.grc.com/

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    Regular Coder brad211987's Avatar
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    also for a quick check on a single port:

    telnet <host> <port>

    If it connects, port is open, otherwise port is closed.

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    If your a Linux bod, the 'nc' command is pretty nice too as in:

    nc 192.168.1.1 80

    Would attempt to connect to port 80. Not as verbose as Telnet, but works where people may have disabled telnet.

    Example HTTP session:

    nc 192.168.1.1 80 {enter}
    GET / HTML/1.1 {enter}
    {enter}
    <OUTPUT>
    HTTP/1.1 200 OK
    Date: Tue, 08 Jun 2010 07:57:25 GMT
    Server: Apache/2.2.9
    Last-Modified: Mon, 22 Mar 2010 11:48:35 GMT
    ETag: "24c88d-e48-4826246ea2ac0"
    Accept-Ranges: bytes
    Content-Length: 3656
    Vary: Accept-Encoding
    Connection: close
    Content-Type: text/html
    {snip}


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