HostPort will check if the host part is a valid IP address, if the IP address is valid, but no port is found, defaultPort is added.

HostPortOrFile parses the strings in s, each string can either be a address, [scheme://]address:port or a filename.

TransferIn parses transfer statements: 'transfer from [address...]'.

Transport returns the transport defined in s and a string where the transport prefix is removed (if there was any).

ErrNoNameservers is returned by HostPortOrFile if no servers can be parsed.