Looking at the documentation [1] and the Streams source code, it appears that the route port for external client boostrap is fixed as 443. Some organizations have policies prohibiting use of this port.

This enhancement would provide a means of overriding this value.

[1] https://access.redhat.com/documentation/en-us/red_hat_amq/7.5/html-single/using_amq_streams_on_openshift/index#proc-accessing-kafka-using-routes-deployment-configuration-kafka