protected void packHeaderInfoForSending(int msgLen, boolean isSecurityHeader) {
    // setting second bit of flags byte for client this is not require but this makes all changes
    // easily at client side right now just see this bit and process security header
    byte flagsByte = flags;
    if (isSecurityHeader) {
      flagsByte |= MESSAGE_HAS_SECURE_PART;
    }
    if (isRetry) {
      flagsByte |= MESSAGE_IS_RETRY;
    }
    getCommBuffer().putInt(messageType.id).putInt(msgLen).putInt(numberOfParts)
        .putInt(transactionId).put(flagsByte);
  }
Adds a new part to this message that may contain a serialized object.
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/Message.java