+------------------------------------------------+
        |                                                |
        | Client                                Server   |
        |                                                |
        |      --------- Q4S READY 0 --------->          |
        |      <-------- Q4S 200 OK -----------          |
        |                                                |
        |      --------- Q4S PING ------------>          |
        |      <-------- Q4S 200 OK -----------          |
        |      <-------- Q4S PING -------------          |
        |       -------- Q4S 200 OK ---------->          |
        |      --------- Q4S PING ------------>          |
        |      <-------- Q4S PING -------------          |
        |      --------- Q4S 200 OK ---------->          |
        |      <-------- Q4S 200 OK -----------          |
        |                     ...                        |
        |                                                |
        +------------------------------------------------+