On some occasions we've been able to fix issues by configuring rhsm_port in /etc/virt-who.conf, for example in RHBZ#1625587.
This parameter is not documented anywhere though, neither in the man page, nor in the product documentation.
The rhsm_port has the default value of 443. Typically. it is not required to change the rhsm_port value.
Satellite does not support using custom ports. Therefore, we cannot add instructions on changing default ports as this can cause errors.