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Tag: telnet

  • using the “telnet” utility for testing ports – it’s sort of gone (on Windows nowadays), but they allow you to re-enable it

    Back in the old days before SSH was “the standard way” to log into a remote computer, there “were” a protocol (and a utility) called “telnet” in order to achieve that.

    But the “telnet” utility traditionally also served for testing deliberate TCP/IP ports somewhere in the Internet resp. on your “Intranet”, e.g.

    Can I connect to that Oracle DB server on that specific port?

    That’s particularly useful, because the applications themselves (whether GUIs or CLI utilities) usually have poor ways of dealing with facts like:

    • some firewall prevents you from accessing that Oracle DB server
    • there is simply no route to that Oracle DB server

    The “telnet” utility does not really have nicer error messages, but “everybody knows”, what it means, if you tell them, you tried to “telnet HOST PORT“, and it failed or timed out. And you know, it’s not the application, but it’s the network or the server.

    In  recent versions of Microsoft Windows the “telnet” utility got made sort of invisible, but there is an easy way to make it visible and available. See the links below!

    But if you already have the PuTTY suite of utilities available on your PC, maybe you prefer the “plink” utility:

    % …plink -telnet -P port host

    The Windows “defect” :mrgreen:  and its fix:

    If you wish to turn on and enable the “telnet” utility, here is what to do:

    1. Click Start.
    2. Click Control Panel.
    3. Now, go to Programs or Programs and Features.
    4. Click Turn Windows features on or off. (only “administrators” can proceed here.)
    5. In the Windows Features dialog box, tick Telnet Client check box.
    6. Click OK.

  • iReport, some Oracle database, JDBC, SQLRunner, …

    Your task is to interface a rather remote Oracle database with iReport.

    But you are not really sure, whether you are able to successfully connect to the database at all.

    And you want to “explore” the database, its tables, its “views” …

    No CLI utility like sqlplus available as well.

    I am trying SQLRunner.

    Says something like “… cannot connect …“.

    I search the web for its precise error message.

    Leads me to a firewall problem, i.e. some firewall prevents me from accessing the Oracle database. Aha?!! The article (on Stackoverflow) says, I should use “telnet” in order to find out, whether I can access the port in question.

    But there is no “telnet” on that Windows PC. Please see my telnet related articles:

    But I have putty available, and I can make putty to react like “telnet with a GUI” – and yes, it looks like, I can’t reach the port at all. Let’s talk to the corporate network support team! But how to tell them, that using telnet I found out, I cannot reach that port? No, I can’t, because there is no telnet, and I can’t tell them of putty, because putty has not got installed properly, I “put” it there myself. What a mess! At least I know, what problem I am dealing with.

    The colleague next to me had somebody solve the firewall problem for her (last week or so). She runs SQLRunner successfully (I showed her). She can properly look at the Oracle tables. She is happy. And I know, I have to get somebody to solve my firewall / network issue. And I will be happy myself “one day”.

    http://Jochen.Hayek.name/wp/blog-en/tag/sqlrunner/ – my SQLRunner related articles