TCP Listen – Firewall Testing Tool

This is a handy little program for testing and troubleshooting.

Enter a port to listen on and it will show incoming connections to that port. This can be useful if you are trying to setup connectivity through a firewall or a router.

This could also be used as a security tool to make it appear you are running a service on a standard port, by having the tool respond, while the services is really running on a different port.

Very small single file is only 48k in size.

Get TCP Listen

TCP Listen


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Responses to “TCP Listen – Firewall Testing Tool”

  1. Chris Avatar

    Any chance I can get the source code for this handy little tool?

    1. Hamato Yoshi Avatar
      Hamato Yoshi

      It’s .NET, just use reflector

  2. Jeremy Avatar
    Jeremy

    A neat enhancement would be to have the tool show which IP the incoming connection came from.

    1. Daryin Jayes Avatar
      Daryin Jayes

      that would be called called peerblock.

  3. Yesu Rathnam Avatar
    Yesu Rathnam

    Hi,

    Is it possible to listen multiple ports at same time. Or can it take source ports from a flat file and listen to all at once.

    1. allscoop Avatar
      allscoop

      Yes, you can listen to multiple ports at once.

  4. Yesu Rathnam Avatar
    Yesu Rathnam

    Any chance that I can get the source code of this tool.

  5. Taz Avatar
    Taz

    Thank you… very usefull!

  6. Kapil Daddikar Avatar
    Kapil Daddikar

    Thanks, simple and useful!

  7. eric Avatar
    eric

    which .net framework version does this application use ?

    1. Mark Avatar
      Mark

      .Net 3.5 is required

  8. Gipper Avatar
    Gipper

    Awesome! exactly what I was looking for… Cheers!

  9. Ashish Shukla Avatar
    Ashish Shukla

    Really very useful tool…. thanks a lot for creating this simple tool.

  10. steve Avatar
    steve

    how do i get listen to listen on a block of 70 ports , without typing all of them in ?

    1. allscoop Avatar

      Sorry, there is not a easier way to add that many ports…

  11. Rene Avatar
    Rene

    This program needs .net 3.5
    Is there also a version suitable for Windows Server 2012?

    1. Dan Avatar
      Dan

      It works fine on Windows Server 2012. I just tried it.

      Thanks for this handy tool.

  12. Ken Fisher Avatar
    Ken Fisher

    Sweet utility. I wish I’d have had this years ago. Very handy for testing.

    Thank-you !!!

  13. Brian Avatar
    Brian

    Hi. Does this create a listener process on the port, similar in the way NetCat does, or does this snoop the interface?

    1. allscoop Avatar
  14. Benudhar Sahoo Avatar
    Benudhar Sahoo

    Nice tool.. antivirus was deleting netcat. this tool saved me 🙂

  15. Hugo Avatar
    Hugo

    THANK YOU!!! If you ever want to enhance it, I suggest to add a multiport (add) system like splited with commas or an interval (x1,x2,x3,…,xn for different ports or y1-y2 for all ports between y1 and y2) or reading from a csv file, or any other simple way. A port stopper would be cool too, and show which IP the incoming connection came from would allow other purposes. And please note Note that this tool is really really great just as it is.

  16. David Avatar
    David

    Great Thanks. Similar to other comments, a way to add multiple ports, or a port range. Even from a .txt file would be good.

    How about a command line option referencing the text file of ports to start monitoring at open.

    Nice simple reliable program. Thanks.

  17. XPaY Avatar
    XPaY

    Brilliant & simple

  18. Mike Juge Avatar

    would there be any chance of a version able to output results in a TXT file? I have to capture raw data from point of sale sources to create a parsers for a data event monitoring solution.

  19. Jose Avatar

    Any chance you could update this to work with .NET 4.6.1?

    1. PC Avatar
      PC

      And 4.6.2?

      1. Jose Avatar
        Jose

        Agreed. Trying to run this on 2012 R2 or 2016 and don’t want to have to use versions of .NET lower than 4.x.

        1. Erik Avatar
          Erik

          Same issue here

  20. Chris Avatar
    Chris

    SIMPLE/Y BEAUTIFUL!

    Thank you!

  21. Jon Avatar
    Jon

    Cool tool but once I try to connect to the port on the 2nd or 3rd time it says an error occured, the port may be in use when running nmap scan against it that specific port

  22. Nozad Avatar
    Nozad

    is there any chance to add port list ?

  23. Luis Avatar
    Luis

    Excellent, very handy, perfect time saver for troubleshooting connectivity errors

  24. UserAtCompany Avatar
    UserAtCompany

    Nice tool!

    though, why, WHY .NET… makes it not a standalone tool :/

  25. Sven Avatar
    Sven

    Thanks a ton. Really handy when I needed this, and an awesome project to add to my collection of tools to write

  26. Alejandro Avatar
    Alejandro

    great tool very helpful thank you guys

  27. Cy Avatar
    Cy

    The program opens on Server 2016, but I can’t get a source computer to connect to any ports I put in. It says it’s listening too. Just wondering if it works for others on Server 2016. Thanks ahead!

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