@Override
  protected byte writeCredential(DataOutputStream dos, DataInputStream dis, String authInit,
      boolean isNotification, DistributedMember member, HeapDataOutputStream heapdos)
      throws IOException, GemFireSecurityException {

    if (!multiuserSecureMode && (authInit == null || authInit.length() == 0)) {
      // No credentials indicator
      heapdos.writeByte(CREDENTIALS_NONE);
      heapdos.flush();
      dos.write(heapdos.toByteArray());
      dos.flush();
      return -1;
    }

    return super.writeCredential(dos, dis, authInit, isNotification, member, heapdos);
  }
client-to-server handshake. Nothing is sent to the server prior to invoking this method.
geode-core/src/main/java/org/apache/geode/cache/client/internal/ClientSideHandshakeImpl.java