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<span>Stem Docs</span></a></h1>
<h2 class="heading"><span>East of the Sun & West of the Moon</span></h2>
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<div class="section" id="east-of-the-sun-west-of-the-moon">
<h1>East of the Sun & West of the Moon<a class="headerlink" href="#east-of-the-sun-west-of-the-moon" title="Permalink to this headline">¶</a></h1>
<p>The following is an overview of some of the utilities stem provides.</p>
<ul class="simple">
<li><a class="reference internal" href="#connection-resolution"><em>Connection Resolution</em></a></li>
</ul>
<div class="section" id="connection-resolution">
<span id="id1"></span><h2>Connection Resolution<a class="headerlink" href="#connection-resolution" title="Permalink to this headline">¶</a></h2>
<p>Connection information is a useful tool for learning more about network
applications like Tor. Our <a class="reference internal" href="../api/util/connection.html#stem.util.connection.get_connections" title="stem.util.connection.get_connections"><tt class="xref py py-func docutils literal"><span class="pre">stem.util.connection.get_connections()</span></tt></a>
function provides an easy method for accessing this information, with a few
caveats...</p>
<ul class="simple">
<li>Connection resolvers are platform specific. We <a class="reference external" href="../api/util/connection.html#stem.util.connection.Resolver">support several</a> but not not
all, most notably Windows (<a class="reference external" href="https://trac.torproject.org/9850">ticket 9850</a>).</li>
<li>By default Tor runs with a feature called <strong>DisableDebuggerAttachment</strong>. This
prevents debugging applications like gdb from analyzing Tor unless it is run
as root. Unfortunately this also alters the permissions of the Tor process
/proc contents breaking numerous system tools (including our resolvers). To
use this function you need to either run as root (discouraged) or add
<strong>DisableDebuggerAttachment 0</strong> to your torrc.</li>
</ul>
<p>Please note that if you operate an exit relay it is <strong>highly</strong> discouraged for
you to look at or record this information. Not only is doing so eavesdropping,
but likely also a violation of wiretap laws.</p>
<p>With that out of the way, how do you look up this information? Below is a
simple script that dumps Tor’s present connections.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">from</span> <span class="nn">stem.util.connection</span> <span class="kn">import</span> <span class="n">get_connections</span><span class="p">,</span> <span class="n">get_system_resolvers</span>
<span class="kn">from</span> <span class="nn">stem.util.system</span> <span class="kn">import</span> <span class="n">get_pid_by_name</span>
<span class="n">resolvers</span> <span class="o">=</span> <span class="n">get_system_resolvers</span><span class="p">()</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">resolvers</span><span class="p">:</span>
<span class="k">print</span> <span class="s">"Stem doesn't support any connection resolvers on our platform."</span>
<span class="n">sys</span><span class="o">.</span><span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="n">picked_resolver</span> <span class="o">=</span> <span class="n">resolvers</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="c"># lets just opt for the first</span>
<span class="k">print</span> <span class="s">"Our platform supports connection resolution via: </span><span class="si">%s</span><span class="s"> (picked </span><span class="si">%s</span><span class="s">)"</span> <span class="o">%</span> <span class="p">(</span><span class="s">', '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">resolvers</span><span class="p">),</span> <span class="n">picked_resolver</span><span class="p">)</span>
<span class="n">tor_pids</span> <span class="o">=</span> <span class="n">get_pid_by_name</span><span class="p">(</span><span class="s">'tor'</span><span class="p">,</span> <span class="n">multiple</span> <span class="o">=</span> <span class="bp">True</span><span class="p">)</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">tor_pids</span><span class="p">:</span>
<span class="k">print</span> <span class="s">"Unable to get tor's pid. Is it running?"</span>
<span class="n">sys</span><span class="o">.</span><span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="k">elif</span> <span class="nb">len</span><span class="p">(</span><span class="n">tor_pids</span><span class="p">)</span> <span class="o">></span> <span class="mi">1</span><span class="p">:</span>
<span class="k">print</span> <span class="s">"You're running </span><span class="si">%i</span><span class="s"> instances of tor, picking the one with pid </span><span class="si">%i</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">tor_pids</span><span class="p">),</span> <span class="n">tor_pids</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">print</span> <span class="s">"Tor is running with pid </span><span class="si">%i</span><span class="s">"</span> <span class="o">%</span> <span class="n">tor_pids</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="k">print</span> <span class="s">"</span><span class="se">\n</span><span class="s">Connections:</span><span class="se">\n</span><span class="s">"</span>
<span class="k">for</span> <span class="n">conn</span> <span class="ow">in</span> <span class="n">get_connections</span><span class="p">(</span><span class="n">picked_resolver</span><span class="p">,</span> <span class="n">process_pid</span> <span class="o">=</span> <span class="n">tor_pids</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">process_name</span> <span class="o">=</span> <span class="s">'tor'</span><span class="p">):</span>
<span class="k">print</span> <span class="s">" </span><span class="si">%s</span><span class="s">:</span><span class="si">%s</span><span class="s"> => </span><span class="si">%s</span><span class="s">:</span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">conn</span><span class="o">.</span><span class="n">local_address</span><span class="p">,</span> <span class="n">conn</span><span class="o">.</span><span class="n">local_port</span><span class="p">,</span> <span class="n">conn</span><span class="o">.</span><span class="n">remote_address</span><span class="p">,</span> <span class="n">conn</span><span class="o">.</span><span class="n">remote_port</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>% python example.py
Our platform supports connection resolution via: proc, netstat, sockstat, lsof, ss (picked proc)
Tor is running with pid 17303
Connections:
192.168.0.1:59014 => 38.229.79.2:443
192.168.0.1:58822 => 68.169.35.102:443</pre>
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