PythonWorkbench
diff --git a/‎can/interfaces/robotell.py‎
Lines changed: 8 additions & 3 deletions b/‎can/interfaces/robotell.py‎
Lines changed: 8 additions & 3 deletions
diff --git a/‎test/test_robotell.py‎
Lines changed: 4 additions & 0 deletions b/‎test/test_robotell.py‎
Lines changed: 4 additions & 0 deletions
@@ -2,6 +2,7 @@
 Interface for Chinese Robotell compatible interfaces (win32/linux).
 """
 
+import io
 import time
 import logging
 
@@ -367,10 +368,14 @@ def shutdown(self):
         self.serialPortOrig.close()
 
     def fileno(self):
-        if hasattr(self.serialPortOrig, "fileno"):
+        try:
             return self.serialPortOrig.fileno()
-        # Return an invalid file descriptor on Windows
-        return -1
+        except io.UnsupportedOperation:
+            raise NotImplementedError(
+                "fileno is not implemented using current CAN bus on this platform"
+            )
+        except Exception as exception:
+            raise CanOperationError("Cannot fetch fileno") from exception
 
     def get_serial_number(self, timeout):
         """Get serial number of the slcan interface.
 
@@ -940,6 +940,10 @@ def test_set_hw_filter(self):
             ),
         )
 
+    def test_when_no_fileno(self):
+        with self.assertRaises(NotImplementedError):
+            self.bus.fileno()
+
 
 if __name__ == "__main__":
     unittest.main()
Original file line number	Diff line number	Diff line change
`@@ -940,6 +940,10 @@ def test_set_hw_filter(self):`
`940`	`940`	`),`
`941`	`941`	`)`
`942`	`942`
	`943`	`+ def test_when_no_fileno(self):`
	`944`	`+ with self.assertRaises(NotImplementedError):`
	`945`	`+ self.bus.fileno()`
	`946`	`+`
`943`	`947`
`944`	`948`	`if __name__ == "__main__":`
`945`	`949`	`unittest.main()`