•check_spooler_session = 1
This enables a periodic check (30 seconds) for idle/lost spooler sessions; that is, sessions that have had no traffic for passive_session_timeout (300) seconds. Among other benefits, it a starvation problem on Windows hubs when a request would be made for a subscription and when it wasn’t responded to in 10 seconds the requester would send a close and close their end. However, because of starvation, not only would the subscription request not get processed, but also the close request – so the connection was left in a half-closed (CLOSE_WAIT) state. As of 7.95 this will be default behavior.
•protocol_mode = 3
This is a variant of protocol_mode 1 with a change in the behavior for handling closes from the “bottom” end. By default, when IM sends a probe_config_get (and now probe_config_set also) request to a remote controller, the controller sends the reply and then sends a close to close the connection from the bottom end. In protocol_mode 0 (the default), the close can cause IM’s local session to be closed before IM has a chance to send its own close request (normally the request originator always sends the close). If this occurs (usually for larger config files), IM assumes the request didn’t complete properly and it issues an error instead of opening the probe config GUI.
•max_heartbeat = 30
Tunnel control heartbeat allows the hub to self-correct OpenSSL session loss or degradation. Network latency and load dependent