DnsUrl.getHostPort() does not take IPv6 colon-separated notation into account:
: host + ":" + port;

Also in DnsClient:
int colon = servers[i].indexOf(':'); // is optional port given?

In toolkit.url.Uri, check that getHost() handles bracketed IPv6 addrs in the
same way as java.net.URI. In fact, consider using the URI class instead of --
or as the implementation of -- the Uri class. Note that the LDAP provider
expects that the result of getHost() may be passed directly to the Socket
constructor or socket factory.