-# the following is equivalent to rwrite(FERROR, "$msg\n")
-# message header: length 17; MPLEX_BASE + code FERROR
+# The following is equivalent to rprintf(FERROR_XFER, "%s\n", $msg).
+# 1. Message header: ((MPLEX_BASE + FERROR_XFER) << 24) + $msglen.