title: Which is the recommended Topic structure in MQTT for private messaging?
body: <p>I am building a MQTT based private messaging application using Eclipse Paho. I am a beginner in MQTT so need to understand implications of Topic architecture.</p>
  
  <p>If user A has to send a message to user B:</p>
  
  <ol>
  <li>make user A subscribe to topic A and user B to topic B. So anyone messaging to B has to publish in topic B (the payload contains the sender details)</li>
  <li>make user A subscribe to A/# and B to B/#. So B messaging to A will publish to topic A/B</li>
  </ol>
  
  <p>I want to know the <strong>recommended topic subscribing</strong> in private messaging considering implementation of other features like </p>
  
  <ol>
  <li>Last Seen</li>
  <li>Online</li>
  <li>Delivered</li>
  <li>Read</li>
  </ol>
  
  <p>Please suggest ways (topic, pub and sub) to implement above features. For example after a client has connected to a broker, it will send a retained message to the topic A/status with the payload “online“.</p>