Got a question about reading and writing data from a child process using named pipes.

I have a pygls language server running as a child process from my main program.

if not os.path.exists(fifo_in_name):
    os.mkfifo(fifo_in_name)
if not os.path.exists(fifo_out_name):
    os.mkfifo(fifo_out_name)
try:
  fifo_in = os.open(fifo_in_name, os.O_RDONLY | os.O_NONBLOCK)
  fifo_out = os.open(fifo_out_name, os.O_WRONLY | os.O_NONBLOCK)
except OSError as e:
  logger.error(f"Failed to open FIFO: {e}")
  raise e


process = await asyncio.create_subprocess_exec(
    sys.executable, 'lsp/lsp_server.py', fifo_in_name, fifo_out_name,
)

In my lsp_server.py, I launch my server like this:

@contextmanager
def open_fifo(name, mode):
    fd = os.open(name, mode | os.O_NONBLOCK)
    try:
        if mode & os.O_RDONLY:
            file_obj = os.fdopen(fd, 'rb', buffering=0)
        elif mode & os.O_WRONLY:
            file_obj = os.fdopen(fd, 'wb', buffering=0)
        else:
            raise ValueError("Unsupported mode")
        yield file_obj
    finally:
        file_obj.close()


if __name__ == "__main__":
    fifo_in = sys.argv[1]
    fifo_out = sys.argv[2]
    with open_fifo(fifo_in, os.O_RDONLY) as f, open_fifo(fifo_out, os.O_WRONLY) as r:
        server.start_io(f, r)
        print("Started LSP server")

I’m getting OSError: [Errno 6] Device not configured: '/tmp/fifo_out' when trying to open fifo_out from my main program. I’d be grateful for some guidance on properly using pipes for bidirectional communication.