Turn off socket inheritance for the wireless device "find calibre" broadcast socket. It appears that calibre restarts otherwise keep this socket open.

src/calibre/devices/smart_device_app/driver.py

@@ -1937,6 +1937,7 @@ def _startup_on_demand(self):
 
             try:
                 self.broadcast_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+                set_socket_inherit(self.broadcast_socket, False)
             except:
                 message = 'creation of broadcast socket failed. This is not fatal.'
                 self._debug(message)