@Override
  public void setSender(InternalDistributedMember _sender) {
    sender = _sender;
  }
Sets the sender of this message. This method is only invoked when the message is
<B>received</B> by a <code>DistributionManager</code>.
geode-core/src/main/java/org/apache/geode/distributed/internal/DistributionMessage.java