#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <sys/timeb.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <signal.h>

#include <errno.h>

#include <stdlib.h>
#include <unistd.h>

#define DEFAULTPORT 1515

#define SUM 0
#define PRODUCT 1


int current_operation;

void sig_handler(int signo)
{
printf("Signal %s received\n",(signo == SIGUSR2)?"SIGUSR2":"SIGUSR1");

  if (signo==SIGUSR2)
    current_operation= SUM;
  else
    current_operation= PRODUCT;

    printf("Current operation is now %s\n",(current_operation==SUM)? "SUM":"PRODUCT");



}




main(int argc,char *argv[])
{
  int	sock,length,  numerolinea, lunghezzalinea;
 struct 	sockaddr_in 	server,client;
 int	msgsock,rval,i;
 int myport;
 struct sigaction sig;

if(argc !=1)
  {
    fprintf(stderr,"Usage: %s\n",argv[0]);
    exit(-1);
  }

printf("Server PID=%d\n",getpid());

 myport = DEFAULTPORT;

 current_operation = SUM ; // inizialmente l'operazione svolta è la somma
  
/* Un unico gestore per entrambi i segnali : 
la sigaction va chiamata due volte, una per ogni segnale  */

 sig.sa_handler = sig_handler;
 sigemptyset(&sig.sa_mask);
 sig.sa_flags=SA_RESTART;

 sigaction(SIGUSR1,&sig,NULL);
 sigaction(SIGUSR2,&sig,NULL);




/* Crea la socket  */
sock=	socket(AF_INET,SOCK_STREAM,0);
if(sock<0)
	{
	perror("open sulla socket dgram");
	exit(1);
	}

/* Name socket using wildcards */
server.sin_family = 	AF_INET;
server.sin_addr.s_addr= INADDR_ANY;
server.sin_port = htons(myport);

if (bind(sock,(struct sockaddr *)&server,sizeof server)<0)
	{
	perror("bind sulla socket dgram");
	exit(1);
	}

/* Find out assigned port and print out */
length= sizeof server;
if(getsockname(sock,(struct sockaddr *)&server,&length)<0)
	{
	perror("getsockname");
	exit(1);
	}

printf("Server running on port #%d\n",ntohs(server.sin_port));

  /* Pronto ad accettare connessioni */

  listen(sock,2);


 do{


 /* Attesa di una connessione */	 
   
   msgsock= accept(sock,(struct sockaddr *)&client,(int *)&length);

   
   if(msgsock ==-1)
     perror("accept");
      else
	{
	  if(fork()==0) // Server è concorrente
	    {
//	      printf("Serving connection from %s, port %d\n",
//		     inet_ntoa(client.sin_addr),
//		     ntohs(client.sin_port));
	      
	      
	      
	      close(sock);

	      servizio(msgsock);
	      close(msgsock);
	      exit(0);
	    }
	  else
	    close(msgsock);
	}
   
 }
 while(1);
}


servizio(int sock)
{
  int rval, n1, n2, result ;
  char buf[256];
  char answer[256];

  memset(buf, 0, sizeof(buf));

  
  if((rval=read(sock,buf, sizeof buf))<0)
   {
     perror("reading filename");
     exit(-1);
   }



  sscanf(buf,"%d %d",&n1,&n2);

  if(current_operation == SUM)
    result = n1 + n2 ;
  else
    if(current_operation == PRODUCT)
      result = n1 * n2 ;


  sprintf(answer,"%d\n",result),

    printf("Received %d %d (current operation %s) = %d\n",n1,n2,(current_operation==SUM)? "SUM":"PRODUCT",result);


  if((rval = write(sock,answer,strlen(answer)+1))<0)
    perror("writing on stream socket");
  
  printf("Service  completed\n");
}