public boolean isNull() {
    if (part == null) {
      return true;
    }
    if (isObject() && part instanceof byte[]) {
      byte[] b = (byte[]) part;
      return b.length == 1 && b[0] == DSCODE.NULL.toByte();
    }
    return false;
  }
Is the payload (<code>part</code>) a serialized object?
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/Part.java