等待模拟时间 Omnet++

Question

I need to modify UdpEchoApp (from Inet package) so that before it sends back the packet it waits "x" seconds of simulation time. I tried doing something like:

simtime_t before;
//something to calculate
simtime_t after;
if (after-before > x) {continue}
else {do something and then recalculate after}

but this crashes Qtenv. Is there something i can do to resolve this problem ? I also post the function that sends back the received packet:

void UdpEchoApp::socketDataArrived(UdpSocket *socket, Packet *pk)
{
    // determine its source address/port
    L3Address remoteAddress = pk->getTag<L3AddressInd>()->getSrcAddress();
    int srcPort = pk->getTag<L4PortInd>()->getSrcPort();
    pk->clearTags();
    pk->trim();

    // statistics
    numEchoed++;
    emit(packetSentSignal, pk);
    // send back
    socket->sendTo(pk, remoteAddress, srcPort);
}

Thank you

Answer 1

Your code is wrong: simulation time is increased by simulation environment according to incoming events. In other words, simulation time is modified outside the standard methods that defines a behavior of a module.
To simulate a delay during the simulation one has to use a selfmessage.
In short:

1. In socketDataArrived() :

• remember the packet to send and remoteAddress in a buffer,
• schedule a selfmessage x seconds later (using scheduleAt() ).

2. In handleMessageWhenUp() when your selfmessage occurs take the packet from the buffer and send it.