Add a copy constructor for class NodePortTuple.
diff --git a/src/main/java/net/floodlightcontroller/topology/NodePortTuple.java b/src/main/java/net/floodlightcontroller/topology/NodePortTuple.java
index 4983529..6ac8f29 100644
--- a/src/main/java/net/floodlightcontroller/topology/NodePortTuple.java
+++ b/src/main/java/net/floodlightcontroller/topology/NodePortTuple.java
@@ -18,6 +18,16 @@
     protected short portId; // switch port id
 
     /**
+     * A copy constructor for NodePortTuple.
+     *
+     * @param other the object to copy the state from.
+     */
+    public NodePortTuple(NodePortTuple other) {
+	this.nodeId = other.nodeId;
+	this.portId = other.portId;
+    }
+
+    /**
      * Creates a NodePortTuple
      * @param nodeId The DPID of the switch
      * @param portId The port of the switch