The hostname can only be supplied being an IP address; DNS names are certainly not permitted. The port in the hostname part may be the TCP listening port. If the TCP and UDP (discovery) ports differ, the UDP port is specified as a question parameter "discport" The opposite significant parameter https://one-directory.com/listings386156/how-much-you-need-to-expect-you-ll-pay-for-a-good-random-ethereum-address