attempt to send CLOSE message on connection close

Author: owenpearson

ably/realtime/connectionmanager.py

@@ -175,7 +175,13 @@ async def close_impl(self) -> None:
         self.cancel_suspend_timer()
         self.start_transition_timer(ConnectionState.CLOSING, fail_state=ConnectionState.CLOSED)
         if self.transport:
-            await self.transport.dispose()
+            # Try to send protocol CLOSE message to server for clean shutdown
+            # If connection is already broken, continue with dispose anyway
+            try:
+                await self.transport.close()
+            except Exception as e:
+                log.debug(f'ConnectionManager.close_impl(): failed to send CLOSE message: {e}')
+            await self.transport.dispose()  # Dispose transport resources
         if self.connect_base_task:
             self.connect_base_task.cancel()
         if self.disconnect_transport_task: