Add dpid to Port JSON object.

Change-Id: I69a78ce0a8cfb07883d4ac13318a7811ab951f02
diff --git a/src/main/java/net/onrc/onos/core/topology/serializers/PortSerializer.java b/src/main/java/net/onrc/onos/core/topology/serializers/PortSerializer.java
index ae75dff..3732151 100644
--- a/src/main/java/net/onrc/onos/core/topology/serializers/PortSerializer.java
+++ b/src/main/java/net/onrc/onos/core/topology/serializers/PortSerializer.java
@@ -8,6 +8,7 @@
 import org.codehaus.jackson.JsonProcessingException;
 import org.codehaus.jackson.map.SerializerProvider;
 import org.codehaus.jackson.map.ser.std.SerializerBase;
+import org.openflow.util.HexString;
 
 public class PortSerializer extends SerializerBase<Port> {
 
@@ -21,6 +22,7 @@
             throws IOException, JsonProcessingException {
         jsonGenerator.writeStartObject();
         jsonGenerator.writeStringField("state", "ACTIVE");
+        jsonGenerator.writeStringField("dpid", HexString.toHexString(port.getDpid()));
         jsonGenerator.writeNumberField("number", port.getNumber());
         jsonGenerator.writeStringField("desc", port.getDescription());
         jsonGenerator.writeArrayFieldStart("devices");