How to send custom packets in omnet++?

Question

Let's say i created my own packet called myPacket. Is there a way i can send it using socket.sendTo() ?

I know socket.sendTo() takes in an INET packet so is there a way to convert myPacket into an INET packet?

The module that is going to receive the packet is Radio. I checked Radio's functions and they take in an inet packet so what can i do about it?

Signal *Radio::createSignal(Packet *packet) const
{
    encapsulate(packet);
    if (sendRawBytes) {
        auto rawPacket = new Packet(packet->getName(), packet->peekAllAsBytes());
        rawPacket->copyTags(*packet);
        delete packet;
        packet = rawPacket;
    }
    Signal *signal = check_and_cast<Signal *>(medium->transmitPacket(this, packet));
    ASSERT(signal->getDuration() != 0);
    return signal;
}

Answer 1

Sending messages using sockets needs a socket on the other side. If you have a socket at the other side so go ahead and send your message using a socket.

Answer 2

Basically, messages sent by using the cSimpleModule basic member function send(). This method is used to send messages to other modules through gates. One can also use the scheduleAt() to send a message at specific point in time.

If you use a higher level application such as http or tcp applications, so you are most probably going to use sockets. Sockets also use send() and scheduleAt() to send messages through gates.

Answer 3

You need to do 4 steps:

1. Define your own.msg class and extend some of the inet predefined classes. See inet/applications/base/ApplicationPacket.msg as an example.
2. Define your communication protocol aka inet socket object to pass the messages. Look at this guide . Don't forget to pass destination address and port, normally they are defined as.NED parameters and injected through the omnetpp.ini file.
3. Then you need to write a method, which builds your packet and sends it to the destination address. Take a look at the method UdpBasicApp::sendPacket() at inet/applications/udpapp/UdpBasicApp.cc as an example.
4. At receiver side I usually have a bunch of processing methods switched in handleMessage method or similar one to catch all possible messages my receiver can receive and process. All such methods take cMessage* msg as an argument and then at the beginning:

Packet* packet = check_and_cast<Packet*>(msg);
if (!packet) {
    return;
}
const auto& payload = packet->peekAtFront<YourOwnPacketClass>();
// work with you message body...