+----------+          +----------+          +----------+
  |QDR.A     |          |QDR.B     |          |QDR.C     |
  |port:     |          |port:     |          |port:     |
  | 20001    |--------->| 20002    |--------->| 20003    |
  |          |          |          |          |          |
  |          |          |          |          |          |
  +----------+          +----------+          +----------+

 * The direction of the arrow shows the direction of the connection setup
   Connector --> Listener