Function check_bind 

pub fn check_bind(
    addr: SocketAddr,
    public_read: bool,
    credential_count: u64,
    demo: bool,
) -> Result<()>

The bind rules of D5. A loopback address needs nothing. Any other address needs --public-read, because viewing is not authenticated, and at least one publish credential (a key or a trust), because publishing is authenticated. A demo needs no credential: its data is generated and in memory, and with none configured every publish is refused, so it is read only.