Signals are received twice in OMNet++ - c++

Question

I have created my own OMNet++ Listener class as follows:
headerfile
#ifndef MYFRAMELISTENER_H_
#define MYFRAMELISTENER_H_
#include <clistener.h>
#include <vector>
class MyFrameListener : public cListener{
public:
int tempDelmeJustForTest;
simsignal_t signalIDArray[14];
int index;
public:
MyFrameListener();
virtual ~MyFrameListener();
virtual void receiveSignal(cComponent *source, simsignal_t signalID, cObject *obj);
};
#endif /* MYFRAMELISTENER_H_ */
cc File
MyFrameListener::MyFrameListener() {
this->tempDelmeJustForTest = 0;
}
MyFrameListener::~MyFrameListener() {
}
void MyFrameListener::receiveSignal(cComponent *source, simsignal_t signalID, cObject *obj){
tempDelmeJustForTest++;
}
SimpleModule cc file:
void ListenersModule::initialize()
{
// TODO - Generated method body
frameListener = new MyFrameListener();
//subscribe("packetReceivedFromLower",frameListener);
simulation.getSystemModule()->subscribe("packetReceivedFromLower",frameListener);
}
void ListenersModule::handleMessage(cMessage *msg)
{
// TODO - Generated method body
}
void ListenersModule::finish(){
//simulation.getSystemModule()->unsubscribe("packetReceivedFromLower",frameListener);
recordScalar("My Listened Values", this->frameListener->tempDelmeJustForTest);
}
Here, I am trying to count the number of Ethernet frames received in EtherMACFullDuplex by incrementing the tempDelmeJustForTest variable.
EtherMACFullDuplex is a module located in inet/src/inet/linklayer/ethernet/EtherMACFullDuplex.cc and it is used to create the Ethernet phy port.
This class has a function as shown below:
void EtherMACFullDuplex::processReceivedDataFrame(EtherFrame *frame)
{
emit(packetReceivedFromLowerSignal, frame);
// strip physical layer overhead (preamble, SFD) from frame
frame->setByteLength(frame->getFrameByteLength());
// statistics
unsigned long curBytes = frame->getByteLength();
numFramesReceivedOK++;
numBytesReceivedOK += curBytes;
emit(rxPkOkSignal, frame);
numFramesPassedToHL++;
emit(packetSentToUpperSignal, frame);
// pass up to upper layer
EV_INFO << "Sending " << frame << " to upper layer.\n";
send(frame, "upperLayerOut");
}
It emits a signal "packetReceivedFromLower" and my listner has subscribed to it as shown in the above code.
Problem is the counter shows tempDelmeJustForTest = 12 when the sender sends only 6 Ethernet Frames. Why ?
Also, I am project referencing Core4Inet project other than the Inet project.

Answer 1

I am guessing you are overhearing the signal emitted by the MAC layer of the destination host and the MAC layer of the switch.
By subscribing not just at your own module, but at the module returned by simulation.getSystemModule(), you are overhearing all signals of type packetReceivedFromLower emitted anywhere in the simulation. The "Subscribing to Signals" chapter of the user manual has more information on this mechanism.
If you want to know where the signal you are overhearing was emitted from, you can use the source parameter of your receiveSignal method.

Answer 2

The counter tempDelmeJustForTest shows 12 when the sender sends 6 Ethernet Frames, because the method processReceivedDataFrame is involved 6 times in your switch and 6 times in destination host.
The command:
simulation.getSystemModule()->subscribe("packetReceivedFromLower",frameListener);
means that the listener will receive the signal from any element (i.e. including switch). You can check which module sent a signal by adding one line in receiveSignal():
void MyFrameListener::receiveSignal(cComponent *source, simsignal_t signalID, cObject *obj){
EV << "Signal from " << source->getFullPath() << endl;
tempDelmeJustForTest++;
}