Can we transmit any data from a custom dashboard TO the robot using UDP ?

[sjspry]

Well, as far as I can tell from rule 75, you can't send operator input which bypasses the driver station.

If you wanted to send something else, you can do it from any port, actually, as long as you have something on the robot to receive it. In Java, at least, you'd use Connector.open("socket://10.xx.yy.5") and related classes. I've not worked with C++, but you could look for the functions "socket", "recv", and "send".