title: Xdebug: [Step Debug] Could not connect to debugging client
body: <p>I would like to try Xdebug 3.0.0RC1 to explore what has changed and the new features that come with it. I am also using the latest PhpStorm 2020.3 EAP which supports Xdebug 3 with no major config needed. Below is my PhpStorm config for the Debugger:</p>
  <p><a href="https://i.stack.imgur.com/Xp3hW.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Xp3hW.png" alt="enter image description here" /></a></p>
  <p>And here is the configuration I have tried for Xdebug3:</p>
  <pre><code>zend_extension=/usr/local/lib/php/extensions/no-debug-non-zts-20170718/xdebug.so
  xdebug.mode=debug
  xdebug.start_with_request=yes
  xdebug.client_host=host.docker.internal # here I tried several combinations like: &quot;localhost&quot;, &quot;127.0.0.1&quot;, &quot;172.17.0.1&quot;
  xdebug.client_port=9001 # here I tried several ports 9003 included with no success
  </code></pre>
  <p>I have also tried not adding the <code>client_host/client_port</code> setting at all and still failing.</p>
  <p>I am getting this error:</p>
  <pre><code>Script php bin/console doctrine:cache:clear-metadata returned with error code 255
  !!  [17-Nov-2020 15:24:40 UTC] Xdebug: [Step Debug] Could not connect to debugging client. Tried: host.docker.internal:9001 (through xdebug.client_host/xdebug.client_port) :-(
  !!  [17-Nov-2020 15:24:41 UTC] PHP Fatal error:  Method class@anonymous::__toString() must not throw an exception, caught Symfony\Component\DependencyInjection\Exception\AutowiringFailedException:  in /var/www/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/Compiler/AutowirePass.php on line 233
  </code></pre>
  <p>Some info about my environment:</p>
  <ul>
  <li>Fedora 33</li>
  <li>Docker version 19.03.13, build 4484c46d9d</li>
  <li>PhpStorm 2020.3 EAP Build #PS-203.5784.36</li>
  </ul>
  <p>It is curious (because apparently <code>host.docker.internal</code> is &quot;not&quot; supported by the Docker version I am using and yet it works) and weird at the same time that the following configuration does work with Xdebug 2 even having the debugger listening for incoming connections all the time:</p>
  <p><a href="https://i.stack.imgur.com/YrkI6.png" rel="noreferrer"><img src="https://i.stack.imgur.com/YrkI6.png" alt="enter image description here" /></a></p>
  <pre><code>zend_extension=/usr/local/lib/php/extensions/no-debug-non-zts-20170718/xdebug.so
  xdebug.remote_autostart=0
  xdebug.remote_enable=1
  xdebug.remote_host=host.docker.internal
  xdebug.remote_port=9000
  </code></pre>
  <p>What I am missing here?</p>
  <p>Note: I already applied the solution provided by the Xdebug developer <a href="https://stackoverflow.com/a/17259423/719427">here</a>.</p>