1. #include <omnetpp.h>
2. //using namespace omnetpp; //for Omnet++ ver. 5
3.  
4. class Server : public cSimpleModule
5. {  
6.   private:
7.     cQueue queue;             //the queue of jobs; it is assumed that the first job in the queue is the one being serviced
8.  cMessage *departure;        //special message; it reminds about the end of service and the need for job departure
9.  simtime_t departure_time;   //time of the next departure
10.  
11.  double L;
12.  int n;
13.  int acc,lost;
14.  
15.   protected:
16.     virtual void initialize();
17.     virtual void handleMessage(cMessage *msgin);
18.  
19. };
20.  
21. Define_Module(Server);
22.  
23.  
24. void Server::initialize()
25. {
26.  departure = new cMessage("Departure");
27.  acc=lost=0;
28.  L=0;
29.  WATCH(L);
30.  n=par("n");
31. }
32.  
33.  
34. void Server::handleMessage(cMessage *msgin)  //two types of messages may arrive: a job from the source, or the special message initiating job departure
35. {  
36.     if (msgin==departure)   //job departure
37.  {
38.   cMessage *msg = (cMessage *)queue.pop();    //remove the finished job from the head of the queue
39.  
40.   send(msg,"out");                            //depart the finished job
41.   if (!queue.isEmpty())                         //if the queue is not empty, initiate the next service, i.e. schedule the next departure event in the future
42.   {
43.    departure_time=simTime()+par("service_time");
44.          scheduleAt(departure_time,departure);
45.   }
46.  }
47.  else if(queue.length()<n)                  //job arrival
48.  {
49.      acc++;
50.   if (queue.isEmpty())
51.   {
52.    departure_time=simTime()+par("service_time");
53.             scheduleAt(departure_time,departure);
54.   }
55.   queue.insert(msgin); //insert the job at the end of the queue
56.  }
57.  else
58.  {
59.      lost++;
60.      delete msgin;
61.  }
62.     L=(double)lost/(acc+lost);
63. }
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