Change port 443 RDP web Client Gateway

Dear Sirs,

We are configurating RDP web cliente.

We want to redirect the port 443 from 4040 but when we change this port, the gateway not open the port.

There is any posibily to change this port.G

Gateway server is a public dns (in order to not use VPN) but in this server, we can add the port.

Best Regards