It seems that this issue also affects any AJAX request that runs for the length of the operation. I’ve tried both using an IFRAME to run my process and an AJAX request (using jQuery). I took your tip and am using a file method to communicate between the visual front end (e.g. progressbar) and...
I too have run into this issue. I’m using a similar method as the original poster to output the progress of COM port operation as it happens. I too would love to see flush supported in the near future.