Hi Howard, Fernando,

Yes ArduinoOTA is very interesting and seems quite Easy...seems !
At the beginning I was thinking it was a listening port problem but i was wrong.
Sorry Howard please forget my last demand.
As i said with ArduinoOTA  I can upload  OCS remotely only the first time when the sketch on the mega is running ArduinoOTA  library.
But when OCS is installed ArduinoOTA is not running and then it is not possible to re-upload, etc...
I did not want to bother Howard with a feature that could work on the side but here again i was wrong.
I'm afraid the ArduinoOTA should be mixed with OCS  not sure Howard would be interested in that.
I can write a little small guide of the first steps to help you save some time.
I'm still testing with a little headache i have to admit.
Tell me if you are interested in that
Hear is the github link i'm using
https://github.com/jandrassy/ArduinoOTA
Juraj is the developer and tried to help me but no solution for the moment

Koal01