The fundamental problem in the example: leader_host = bigdata.example.org:10443 is ":10443" is not part of the hostname. The field is called "leader_host"

The fundamental problem in the example: leader_host = bigdata.example.org:10443 is ":10443" is not part of the hostname. The field is called "leader_host"; if a port is needed, it should use it's own field instead of trying to overload the host field. leader_host = bigdata.example.org leader_port = 10443 (and as as others have already mentioned, don't write your own parser when they already exist in your stdlib/etc)