On Windows, configuring a named pipe server with pipe_mode will force ServerOptions::reject_remote_clients as false.
This drops any intended explicit configuration for the reject_remote_clients that may have been set as true previously.
The default setting of reject_remote_clients is normally true meaning the default is also overridden as false.
Workarounds
Ensure that pipe_mode is set first after initializing a ServerOptions. For example:
let mut opts = ServerOptions::new();
opts.pipe_mode(PipeMode::Message);
opts.reject_remote_clients(true);