title: libev, why recv a event's number is 3 in evloop?
body: <pre><code>void callback(struct ev_loop *loop, ev_io *w, int events)
  {
      if (EV_READ == events) {
        ...
      }
      else if (EV_WRITE == events) {
        ...
      }
      else {
        here recv event's number is 3
      }
  }
  </code></pre>
  
  <p>In libev source code 'ev.h', i had not been find macro to define number 0x03 </p>
  
  <pre><code>EV_READ     =            0x01, /* ev_io detected read will not block */
  EV_WRITE    =            0x02, /* ev_io detected write will not block */
  </code></pre>