code: public static Name
  fromAddress(String addr) throws UnknownHostException {
  	byte [] array = Address.toByteArray(addr, Address.IPv4);
  	if (array == null)
  		array = Address.toByteArray(addr, Address.IPv6);
  	if (array == null)
  		throw new UnknownHostException("Invalid IP address");
  	return fromAddress(array);
  }
docs: Creates a reverse map name corresponding to an address contained in
  a String.
  @param addr The address from which to build a name.
  @return The name corresponding to the address in the reverse map.
  @throws UnknownHostException The string does not contain a valid address.