FreeBSD's services file contains an additional echo service entry, with

a non-standard protocol and on a lower port than the tcp/udp entries,
which breaks the assumption that there will only be one service by a
given name on a given port when no protocol is specified.

Previous versions of this code have had other problems as a result of
different service definitions amongst common platforms.  As this platform
has an extra, unexpected, service entry, I've special cased the platform
rather than re-order the list of services checked to highlight the pitfall.