+------------------------------------------------+
        |                                                |
        | Client             Server             Actuator |
        |        ...                                     |
        |   --- PING ---------->                         |
        |   <-- 200 OK----------                         |
        |   <----- PING --------                         |
        |   <--- 200 OK -------- ---- alert              |
        |                            notification -->    |
        |                                                |
        |   --- PING ----------> <--- alert              |
        |                             acknowledge ---    |
        |   <-- 200 OK----------                         |
        |   <----- PING --------                         |
        |   --- 200 OK -------->                         |
        |        ...                                     |
        |                                                |
        +------------------------------------------------+