Re-ping if we are downloading

Don't disconnect.  Send multiple pings during large downloads.  Only disconn if _last_mg_in outside keep alive

Don't close socket if _last_mg_in was within keep alive (don't rely on _ping_t only)

Send out pingreq, do not disconnect, if downloading, or pingreq overdue.

REvert loop misc but make it only disconnect on _last_msg_in, not _ping_t

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Disconnect if no ping response, but if downloading ping again, resetting _ping_t

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Only re-ping if we are downloading

Author: JamesParrott

src/paho/mqtt/client.py

@@ -2174,6 +2174,8 @@ def loop_misc(self) -> MQTTErrorCode:
 
         return MQTTErrorCode.MQTT_ERR_SUCCESS
 
+
+
     def max_inflight_messages_set(self, inflight: int) -> None:
         """Set the maximum number of messages with QoS>0 that can be part way
         through their network flow at once. Defaults to 20."""
@@ -3274,7 +3276,7 @@ def _check_keepalive(self) -> None:
             last_msg_in = self._last_msg_in
 
         if self._sock is not None and (now - last_msg_out >= self._keepalive or now - last_msg_in >= self._keepalive):
-            if self._state == _ConnectionState.MQTT_CS_CONNECTED and self._ping_t == 0:
+            if self._state == _ConnectionState.MQTT_CS_CONNECTED and (self._ping_t == 0 or now - last_msg_in < self.keepalive):
                 try:
                     self._send_pingreq()
                 except Exception: