// Send close_notify alert.
if (PR_Shutdown(nspr, PR_SHUTDOWN_BOTH) != PR_SUCCESS) {
  const PRErrorCode err = PR_GetError();
  fprintf(stderr, "error: PR_Read error %d: %s\n",
	    err, PR_ErrorToName(err));
  exit(1);
}
// Closes the underlying POSIX file descriptor, too.
PR_Close(nspr);