I have test bot the `rpc.ruserd` and `rusers` on localhost, including version 3 and 2 (`RPC_PROGVERSMISMATCH`), from `inetd` or run directly.
```
kola@freebsd:/usr/src/libexec/rpc.rusersd $ sudo rusers localhost // Version 3
localhost kola kola kola kola kola kola
kola@freebsd:/usr/src/libexec/rpc.rusersd $ sudo rusers localhost // Version 2
RPC_PROGVERSMISMATCH // debug log
localhost kola kola kola kola kola kola
```