Working on the cluster i/o
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/EchoMessage.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/EchoMessage.java
new file mode 100644
index 0000000..d25a341
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/EchoMessage.java
@@ -0,0 +1,37 @@
+package org.onlab.onos.store.cluster.messaging;
+
+import org.onlab.onos.cluster.NodeId;
+
+/**l
+ * Echo heart-beat message that nodes send to each other.
+ */
+public class EchoMessage extends ClusterMessage {
+
+ private NodeId nodeId;
+
+ // For serialization
+ private EchoMessage() {
+ super(MessageSubject.HELLO);
+ nodeId = null;
+ }
+
+ /**
+ * Creates a new heart-beat echo message.
+ *
+ * @param nodeId sending node identification
+ */
+ public EchoMessage(NodeId nodeId) {
+ super(MessageSubject.HELLO);
+ nodeId = nodeId;
+ }
+
+ /**
+ * Returns the sending node identifer.
+ *
+ * @return node identifier
+ */
+ public NodeId nodeId() {
+ return nodeId;
+ }
+
+}