IdM behind a firewall

[tmontanaro]

I'm trying to execute the FIWARE Idm behind a firewall (I'm using the docker version), but it is really difficult because it seems that some background parts use a range of ports to connect to the (i think it is a) backend. Specifically, I noticed (through tshark) that it uses a port among 47870 and 47900 to run the server, but I'm not sure they are limited to this range only.

Is there any way of specifying such interval or, better, choose a fixed port?

Thank you in advance