PiggyBackService: fixed null-pointer on piggyback-receive if no local

service is registered.

src/de/tud/kom/p2psim/impl/transport/modular/ModularTransLayer.java

@@ -319,8 +319,7 @@ public class ModularTransLayer implements SimHostComponent, TransportComponent,
 				for (PiggybackMessageService pService : piggybackServices
 						.values()) {
 					piggybacked = pService.piggybackOnSendMessage(receiverNet,
-							receiverPort,
-							ProtocolAdapter.this);
+							receiverPort, ProtocolAdapter.this);
 					if (piggybacked != null) {
 						if (mPig == null) {
 							mPig = new MessageWithPiggybackedData(msg);
@@ -430,7 +429,6 @@ public class ModularTransLayer implements SimHostComponent, TransportComponent,
 			}
 		}
 
-
 		/*
 		 * Notify the Protocol of a received Message
 		 */
@@ -465,7 +463,8 @@ public class ModularTransLayer implements SimHostComponent, TransportComponent,
 					// triggered once
 
 					if (receivedMessage.getPayload() instanceof MessageWithPiggybackedData) {
-						MessageWithPiggybackedData pMsg = (MessageWithPiggybackedData) receivedMessage.getPayload();
+						MessageWithPiggybackedData pMsg = (MessageWithPiggybackedData) receivedMessage
+								.getPayload();
 						/*
 						 * Deliver piggybacked messages
 						 */
@@ -478,8 +477,8 @@ public class ModularTransLayer implements SimHostComponent, TransportComponent,
 						// deliver real message
 						replyEvent.success(pMsg.getPayload(), senderInfo);
 					} else {
-						replyEvent
-							.success(receivedMessage.getPayload(), senderInfo);
+						replyEvent.success(receivedMessage.getPayload(),
+								senderInfo);
 					}
 				}
 				/*
@@ -497,13 +496,15 @@ public class ModularTransLayer implements SimHostComponent, TransportComponent,
 					MessageWithPiggybackedData pMsg = (MessageWithPiggybackedData) receivedMessage
 							.getPayload();
 					/*
-					 * Deliver piggybacked messages
+					 * Deliver piggybacked messages, but only if we have a local
+					 * listener. Discard otherwise.
 					 */
 					for (Entry<Byte, Message> entry : pMsg.getPiggybacked()
 							.entrySet()) {
-						piggybackServices.get(entry.getKey())
-								.onReceivedPiggybackedMessage(entry.getValue(),
-										senderInfo);
+						PiggybackMessageService service = piggybackServices.get(entry.getKey());
+						if (service != null) {
+							service.onReceivedPiggybackedMessage(entry.getValue(), senderInfo);
+						}
 					}
 					// deliver real message
 					pl.dispatch(pMsg.getPayload(), protocol, senderInfo,