title: When I should use zmq_msg_t?
body: <p>The functions for sending and receiving messages as follows:</p>
  
  <pre><code>int zmq_send (void *socket, void *buf, size_t len, int flags);
  int zmq_recv (void *socket, void *buf, size_t len, int flags);
  </code></pre>
  
  <p>However, from documentation it's not clear when I have to use <code>zmq_msg_t</code> or my custom data directly. So in which cases I should consider using <code>zmq_msg_t</code> and in which case send my data directly?</p>