simple Txc1
{
    gates:
        input in;
        output out;
}

//
// Two instances (tic and toc) of Txc1 connected both ways.
// Tic and toc will pass messages to one another.
//
network Tictoc1
{
    submodules:
        tic: Txc1;
        toc: Txc1;

    connections:

        tic.out --> {  delay = 100ms; } --> toc.in;
        tic.in <-- {  delay = 100ms; } <-- toc.out;
}

#include <string.h>
#include <omnetpp.h>

using namespace omnetpp;

/**
 * Derive the Txc1 class from cSimpleModule. In the Tictoc1 network,
 * both the `tic' and `toc' modules are Txc1 objects, created by OMNeT++
 * at the beginning of the simulation.
 */
class Txc1 : public cSimpleModule
{
  protected:
    // The following redefined virtual function holds the algorithm.
    virtual void initialize() override;
    virtual void handleMessage(cMessage *msg) override;
};

// The module class needs to be registered with OMNeT++
Define_Module(Txc1);

void Txc1::initialize()
{
    // Initialize is called at the beginning of the simulation.
    // To bootstrap the tic-toc-tic-toc process, one of the modules needs
    // to send the first message. Let this be `tic'.

    // Am I Tic or Toc?

    //仿真初始化，由节点tic发出第一条消息
    if (strcmp("tic", getName()) == 0) {
        // create and send first message on gate "out". "tictocMsg" is an
        // arbitrary string which will be the name of the message object.
        //创建输出门“out”发出第一条消息"tictocMsg"，不过发的啥这里并不关心
        cMessage *msg = new cMessage("tictocMsg");
        send(msg, "out");
    }
}

void Txc1::handleMessage(cMessage *msg)
{
    // The handleMessage() method is called whenever a message arrives
    // at the module. Here, we just send it to the other module, through
    // gate `out'. Because both `tic' and `toc' does the same, the message
    // will bounce between the two.

    send(msg, "out"); // send out the message
}