Repeated communication between RSU and vehicle

Question

I encounter some trouble when using VEINS. I want to simulate a comunication between RSU and Vehicle. in the begining of simulation, RSU broadcasts a MsgInit message to all vehicles, after that, the vehicles also broadcasts a Metrics message to RSU. But RSU cannot received the Metrics message, I dont know the reason, can someone help me? Here is my code (I'm using omnet 5.6.2, sumo 1.8.0 and veins 5.1)

// MyVeinsAppRSU.cc
void MyVeinsAppRSU::initialize(int stage)
{
    ...
    // send message "sendMsgInit" at 70 second of simulation
    scheduleAt(simTime()+70,sendMsgInit);
}
void MyVeinsAppRSU::handleSelfMsg(cMessage* msg)
{
    MsgInit* msg_init = new MsgInit();
    BaseFrame1609_4* WSM = new BaseFrame1609_4();
    WSM->encapsulate(msg_init);
    populateWSM(WSM);
    // send out WSM from lowerLayer of Application of RSU
    send(WSM,lowerLayerOut);
}
void MyVeinsAppRSU::handleLowerMsg(cMessage* msg)
{
    BaseFrame1609_4* WSM = check_and_cast<BaseFrame1609_4*>(msg);
    //Decapsulation packet from WSM
    cPacket* pkt = WSM->getEncapsulatedPacket();
    // translate packet to Metrics
    Metrics* MT = dynamic_cast<Metrics*>(pkt);
    EV << "send message Vehicle id: " << MT->getVehicleId() << "Receive successfully !!!!!!!!!!!" << endl;
}

// MyVeinsAppCar.cc
void MyVeinsAppCar::handleLowerMsg(cMessage* msg)
{
    BaseFrame1609_4* WSM = check_and_cast<BaseFrame1609_4*>(msg);
    cPacket* enc = WSM->getEncapsulatedPacket();
    MsgInit* MI = dynamic_cast<MsgInit*>(enc);
    // initialize as follower
    findHost()->getDisplayString().setTagArg("i", 1, "black");

    //after receive MsgInit, send Metrics out(next step: handleSelfMsg)
    if (sendMetrics->isScheduled()) {
        cancelEvent(sendMetrics);
    }
    scheduleAt(simTime() + 1,sendMetrics);
}
void MyVeinsAppCar::handleSelfMsg(cMessage* msg)
{
    cModule* vehicle = getParentModule();
    TraCIMobility* traci = dynamic_cast<TraCIMobility*>(vehicle->getSubmodule("veinsmobility", 0));
    TraCICommandInterface::Vehicle* traciVehicle = traci->getVehicleCommandInterface();

    if(msg == sendMetrics){

        Metrics* msg_metrics = new Metrics();
        msg_metrics->setVehicleId(this->getParentModule()->getIndex());
        msg_metrics->setSpeed(traci->getSpeed());

        BaseFrame1609_4* WSM = new BaseFrame1609_4();
        WSM->encapsulate(msg_metrics);
        populateWSM(WSM, -1);
        send(WSM,lowerLayerOut);

        EV << "send Metrics!!"<< endl;
    }
}

Thank you in advance.