Fix is_connected property when not using loop_forever

ChangeLog.txt

@@ -23,6 +23,10 @@ v2.0.0 - 2023-xx-xx
 - Fix loading too weak TLS CA file but setting allowed ciphers before loading CA. Closes #676.
 - Allow to manually ack QoS > 0 messages. Closes #753 & #348.
 - Improve tests & linters. Modernize build (drop setup.py, use pyproject.toml)
+- Fix is_connected property to correctly return False when connection is lost
+  and loop_start/loop_forever isn't used. Closes #525.
+
+
 
 v1.6.1 - 2021-10-21
 ===================

src/paho/mqtt/client.py

@@ -1290,10 +1290,19 @@ def _loop(self, timeout: float = 1.0) -> MQTTErrorCode:
             socklist = select.select(rlist, wlist, [], timeout)
         except TypeError:
             # Socket isn't correct type, in likelihood connection is lost
+            # ... or we called disconnect(). In that case the socket will
+            # be closed but some loop (like loop_forever) will continue to
+            # call _loop(). We still want to break that loop by returning an
+            # rc != MQTT_ERR_SUCCESS and we don't want state to change from
+            # mqtt_cs_disconnecting.
+            if self._state != ConnectionState.MQTT_CS_DISCONNECTING:
+                self._state = ConnectionState.MQTT_CS_CONNECTION_LOST
             return MQTTErrorCode.MQTT_ERR_CONN_LOST
         except ValueError:
             # Can occur if we just reconnected but rlist/wlist contain a -1 for
             # some reason.
+            if self._state != ConnectionState.MQTT_CS_DISCONNECTING:
+                self._state = ConnectionState.MQTT_CS_CONNECTION_LOST
             return MQTTErrorCode.MQTT_ERR_CONN_LOST
         except Exception:
             # Note that KeyboardInterrupt, etc. can still terminate since they
@@ -1768,6 +1777,8 @@ def loop_misc(self) -> MQTTErrorCode:
             if self._state == mqtt_cs_disconnecting:
                 rc = MQTTErrorCode.MQTT_ERR_SUCCESS
             else:
+                self._state = ConnectionState.MQTT_CS_CONNECTION_LOST
+                self._easy_log(MQTT_LOG_DEBUG, "... 2")
                 rc = MQTTErrorCode.MQTT_ERR_KEEPALIVE
 
             self._do_on_disconnect(rc)
@@ -2580,6 +2591,10 @@ def _loop_rc_handle(
 
             self._do_on_disconnect(rc, properties)
 
+        if rc == MQTT_ERR_CONN_LOST:
+            self._easy_log(MQTT_LOG_DEBUG, "... 3")
+            self._state = ConnectionState.MQTT_CS_CONNECTION_LOST
+
         return rc
 
     def _packet_read(self) -> MQTTErrorCode:

src/paho/mqtt/enums.py

@@ -68,6 +68,7 @@ class ConnectionState(enum.IntEnum):
     MQTT_CS_CONNECTED = 1
     MQTT_CS_DISCONNECTING = 2
     MQTT_CS_CONNECT_ASYNC = 3
+    MQTT_CS_CONNECTION_LOST = 4
 
 
 class MessageState(enum.IntEnum):