Dude Agent port behind a NAT

How to connect to an agent to a different port than 8291?
It seems it can’t be done…

Dude works on WinBox port.

Wysłane z mojego Redmi Note 3 przy użyciu Tapatalka

The matter is that dude box is behind a mikrotik box doing NAT, so, how to connect to an agent with a different tcp port if 8291 is get by first box?
In “device” panel there’s no place to specify the dude port, only a checkbox “dude server”.

Thanks