Fixes the unexpected implementation of the ModbusSerialClient.connected property (#2327)

Author: MAKOMO

pymodbus/client/serial.py

@@ -208,9 +208,9 @@ def __init__(  # pylint: disable=too-many-arguments
         self.silent_interval = round(self.silent_interval, 6)
 
     @property
-    def connected(self):
-        """Connect internal."""
-        return self.connect()
+    def connected(self) -> bool:
+        """Check if socket exists."""
+        return self.socket is not None
 
     def connect(self) -> bool:
         """Connect to the modbus serial server."""

pymodbus/client/tcp.py

@@ -160,7 +160,7 @@ def __init__(
 
     @property
     def connected(self) -> bool:
-        """Connect internal."""
+        """Check if socket exists."""
         return self.socket is not None
 
     def connect(self):