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<meta itemprop="headline" content="SSH into Machine That Is Behind a Private Network">
<meta itemprop="description" content="StoryI believe there is always a “tech support person” in every home. Everyone knows that when there is a problem with any electronic device, they should ask this person. I am the tech support in our house. Today, I had to fix a problem in our desktop. Since I was not at home, I had to fix the problem remotely.">
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<h1 id="page-title" class="page__title" itemprop="headline">SSH into Machine That Is Behind a Private Network
</h1>
<p class="page__meta">
<span class="page__meta-date">
<i class="far fa-calendar-alt" aria-hidden="true"></i>
<time datetime="2022-02-26T21:40:00+00:00">February 26, 2022</time>
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<span class="page__meta-sep"></span>
<span class="page__meta-readtime">
<i class="far fa-clock" aria-hidden="true"></i>
2 minute read
</span>
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<section class="page__content" itemprop="text">
<h2 id="story">Story</h2>
<p>I believe there is always a “tech support person” in every home. Everyone knows that when there is a problem with any electronic device, they should ask this person. I am the tech support in our house. Today, I had to fix a problem in our desktop. Since I was not at home, I had to fix the problem remotely.</p>
<h2 id="possible-solutions">Possible solutions</h2>
<ul>
<li>
<p>Just tell the non-tech people at home to configure the router to forward ssh traffic to desktop, right? Well, this is not an option for me, not because people are non-tech, but there is no router! The desktop is connected to internet via hotspot from mobile phone. There is no root access in the phone and even if there was, it is a really big pain to forward the packets manually. Trust me. Been there, done that!</p>
</li>
<li>
<p>There are tools like <a href="https://www.ngrok.com">ngrok</a>, <a href="localtunnel.me">localtunnel</a> which exposes your localhost to the internet and gives you a URL to access it but I did not want to use them.</p>
<ul>
<li>I did not want to use <code class="language-plaintext highlighter-rouge">ngrok</code> because it is not open source and it might have security issues. They are also charging you.</li>
<li><code class="language-plaintext highlighter-rouge">localtunnel</code> seemed perfect. The code of both client and server is open. That is great news! But it did not last long because it is just forwarding http/https traffic :(</li>
</ul>
</li>
</ul>
<h2 id="solution">Solution</h2>
<p>I was thinking of extending the functionality of <code class="language-plaintext highlighter-rouge">localtunnel</code>, but I learned a very simple way. You dont need any external program to overcome this issue. The good old <code class="language-plaintext highlighter-rouge">ssh</code> can do that! All you need is another machine (a remote server) that both computers can access via ssh.</p>
<div class="language-bash highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c"># local machine (my home computer)</span>
ssh <span class="nt">-R</span> 7777:localhost:22 remote-user@remote.host
</code></pre></div></div>
<p>This command forwards all the incoming connections to port 7777 of remote machine to port 22 of our current machine. In order for this to work, you need to make sure <code class="language-plaintext highlighter-rouge">GatewayPorts</code> is set to <code class="language-plaintext highlighter-rouge">yes</code> in the remote server ssh configuration. It also assumes our current machine accepts ssh connections via port 22.</p>
<hr />
<p>Now, go to any machine and connect to the remote server first. When we are connected, we will create another ssh connection to port 7777 to connect our home computer.</p>
<div class="language-bash highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c"># another local machine (my laptop)</span>
ssh remote-user@remote.host
<span class="c"># connected remote</span>
ssh <span class="nt">-p</span> 7777 homeuser@localhost
<span class="c"># we are now connected to home computer</span>
</code></pre></div></div>
<p>The last two command can also combined so that we directly hop into the home computer.</p>
<div class="language-bash highlighter-rouge"><div class="highlight"><pre class="highlight"><code>ssh <span class="nt">-t</span> remote-user@remote.host ssh <span class="nt">-p</span> 7777 homeuser@localhost
</code></pre></div></div>
<h3 id="result">Result</h3>
<p>As a result, it only took us 2 simple ssh commands to do this. This is just unbelievable! Now, I need to find a way to make non-tech people at home run this command when there is a problem. Too bad Linux cant help me there :D</p>
</section>
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<p class="page__date"><strong><i class="fas fa-fw fa-calendar-alt" aria-hidden="true"></i> Updated:</strong> <time datetime="2022-02-26T21:40:00+00:00">February 26, 2022</time></p>
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