Dear Gunter, 
There would be no such option.
At an SAP ABAP system, it is the Gateway process that receives / handles RFC communication with remote systems, and the Gateway does not have the option to bind to multiple ports.
The Gateway can bind to only two ports:
- sapgw<xx> (33xx/tcp) - for "normal" RFC communication; and
- sapgw<xx>s (48xx/tcp) - for RFC communication with SNC enabled.
Regards,
Isaías