ter-item expanded "><a href="../../chapter_9/9.2/9.2.2.html"><strong aria-hidden="true">9.2.2.</strong> MQTT Principles</a></li><li class="chapter-item expanded "><a href="../../chapter_9/9.2/9.2.3.html"><strong aria-hidden="true">9.2.3.</strong> MQTT Message Format</a></li><li class="chapter-item expanded "><a href="../../chapter_9/9.2/9.2.4.html"><strong aria-hidden="true">9.2.4.</strong> Protocol Comparison</a></li><li class="chapter-item expanded "><a href="../../chapter_9/9.2/9.2.5.html"><strong aria-h