{"id":7212,"date":"2017-02-10T13:21:36","date_gmt":"2017-02-10T12:21:36","guid":{"rendered":"http:\/\/www.b.shuttle.de\/hayek\/hayek\/jochen\/wp\/blog-en\/?p=7212"},"modified":"2017-02-10T13:21:36","modified_gmt":"2017-02-10T12:21:36","slug":"the-telnet-utility","status":"publish","type":"post","link":"https:\/\/wp.jochen.hayek.name\/blog-en\/2017\/02\/10\/the-telnet-utility\/","title":{"rendered":"using the &#8220;telnet&#8221; utility for testing ports \u2013 it&#8217;s sort of gone (on Windows nowadays), but they allow you to re-enable it"},"content":{"rendered":"<p>\t\t\t\tBack in the old days before <em>SSH<\/em> was &#8220;the standard way&#8221; to log into a remote computer, there &#8220;were&#8221; a protocol (and a utility) called &#8220;<em>telnet<\/em>&#8221; in order to achieve that.<\/p>\n<p>But the &#8220;<em>telnet<\/em>&#8221; utility traditionally also served for testing deliberate TCP\/IP ports somewhere in the Internet resp. on your &#8220;Intranet&#8221;, e.g.<\/p>\n<blockquote><p>Can I connect to that Oracle DB server on that specific port?<\/p><\/blockquote>\n<p>That&#8217;s particularly useful, because the applications themselves (whether GUIs or CLI utilities) usually have poor ways of dealing with facts like:<\/p>\n<ul>\n<li>some firewall prevents you from accessing that Oracle DB server<\/li>\n<li>there is simply no route to that Oracle DB server<\/li>\n<\/ul>\n<p>The &#8220;<em>telnet<\/em>&#8221; utility does not really have nicer error messages, but &#8220;everybody knows&#8221;, what it means, if you tell them, you tried to &#8220;<em>telnet HOST PORT<\/em>&#8220;, and it failed or timed out. And you know, it&#8217;s not the application, but it&#8217;s the network or the server.<\/p>\n<p>In \u00a0recent versions of Microsoft Windows the &#8220;<em>telnet<\/em>&#8221; utility got made sort of invisible, but there is an easy way to make it visible and available. See the links below!<\/p>\n<p>But if you already have the PuTTY suite of utilities available on your PC, maybe you prefer the &#8220;plink&#8221; utility:<\/p>\n<ul>\n<li><a href=\"https:\/\/the.earth.li\/~sgtatham\/putty\/0.67\/htmldoc\/Chapter7.html#plink-usage\">https:\/\/the.earth.li\/~sgtatham\/putty\/0.67\/htmldoc\/Chapter7.html#plink-usage<\/a><\/li>\n<\/ul>\n<pre>% \u2026plink -telnet -P <em>port<\/em>\u00a0<em>host<\/em><\/pre>\n<ul>\n<li><a href=\"http:\/\/www.chiark.greenend.org.uk\/~sgtatham\/putty\/latest.html\">http:\/\/www.chiark.greenend.org.uk\/~sgtatham\/putty\/latest.html<\/a>\u00a0&#8211; where to find the PuTTY suite of utilities<\/li>\n<\/ul>\n<p>The Windows &#8220;defect&#8221; <img data-recalc-dims=\"1\" src=\"https:\/\/i0.wp.com\/wp.jochen.hayek.name\/blog-en\/wp-includes\/images\/smilies\/mrgreen.png?ssl=1\" alt=\":mrgreen:\" class=\"wp-smiley\" style=\"height: 1em; max-height: 1em;\" \/> \u00a0and its fix:<\/p>\n<ul>\n<li><a href=\"http:\/\/superuser.com\/questions\/349080\/is-there-a-telnet-utility-for-windows\">http:\/\/superuser.com\/questions\/349080\/is-there-a-telnet-utility-for-windows<\/a><\/li>\n<li><a href=\"http:\/\/superuser.com\/questions\/110760\/why-isnt-telnet-enabled-by-default-in-windows-7\">http:\/\/superuser.com\/questions\/110760\/why-isnt-telnet-enabled-by-default-in-windows-7<\/a><\/li>\n<li><a href=\"http:\/\/www.webtlk.com\/2009\/07\/24\/how-to-enable-telnet-in-windows-vista-and-windows-7\/\">http:\/\/www.webtlk.com\/2009\/07\/24\/how-to-enable-telnet-in-windows-vista-and-windows-7\/<\/a><\/li>\n<\/ul>\n<p>If you wish to turn on and enable the &#8220;telnet&#8221; utility, here is what to do:<\/p>\n<ol>\n<li>Click Start.<\/li>\n<li>Click Control Panel.<\/li>\n<li>Now, go to Programs or Programs and Features.<\/li>\n<li>Click Turn Windows features on or off. (only &#8220;administrators&#8221; can proceed here.)<\/li>\n<li>In the Windows Features dialog box, tick Telnet Client check box.<\/li>\n<li>Click OK.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Back in the old days before SSH was &#8220;the standard way&#8221; to log into a remote computer, there &#8220;were&#8221; a protocol (and a utility) called &#8220;telnet&#8221; in order to achieve that. But the &#8220;telnet&#8221; utility traditionally also served for testing deliberate TCP\/IP ports somewhere in the Internet resp. on your &#8220;Intranet&#8221;, e.g. Can I connect [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"_share_on_mastodon":"0"},"categories":[475,666],"tags":[1337],"class_list":["post-7212","post","type-post","status-publish","format-standard","hentry","category-putty","category-uncategorized","tag-telnet"],"share_on_mastodon":{"url":"","error":""},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paO0kP-1Sk","jetpack_likes_enabled":true,"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/posts\/7212","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/comments?post=7212"}],"version-history":[{"count":0,"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/posts\/7212\/revisions"}],"wp:attachment":[{"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/media?parent=7212"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/categories?post=7212"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.jochen.hayek.name\/blog-en\/wp-json\/wp\/v2\/tags?post=7212"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}